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Daigle A, Johri P. Hill-Robertson interference may bias the inference of fitness effects of new mutations in highly selfing species. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.06.579142. [PMID: 38370745 PMCID: PMC10871249 DOI: 10.1101/2024.02.06.579142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
The accurate estimation of the distribution of fitness effects (DFE) of new mutations is critical for population genetic inference but remains a challenging task. While various methods have been developed for DFE inference using the site frequency spectrum of putatively neutral and selected sites, their applicability in species with diverse life history traits and complex demographic scenarios is not well understood. Selfing is common among eukaryotic species and can lead to decreased effective recombination rates, increasing the effects of selection at linked sites, including interference between selected alleles. We employ forward simulations to investigate the limitations of current DFE estimation approaches in the presence of selfing and other model violations, such as linkage, departures from semidominance, population structure, and uneven sampling. We find that distortions of the site frequency spectrum due to Hill-Robertson interference in highly selfing populations lead to mis-inference of the deleterious DFE of new mutations. Specifically, when inferring the distribution of selection coefficients, there is an overestimation of nearly neutral and strongly deleterious mutations and an underestimation of mildly deleterious mutations when interference between selected alleles is pervasive. In addition, the presence of cryptic population structure with low rates of migration and uneven sampling across subpopulations leads to the false inference of a deleterious DFE skewed towards effectively neutral/mildly deleterious mutations. Finally, the proportion of adaptive substitutions estimated at high rates of selfing is substantially overestimated. Our observations apply broadly to species and genomic regions with little/no recombination and where interference might be pervasive.
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Affiliation(s)
- Austin Daigle
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Parul Johri
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599
- Department of Genetics, University of North Carolina, Chapel Hill, NC 27599
- Integrative Program for Biological & Genome Sciences, University of North Carolina, Chapel Hill, NC 27599
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Collet JM, Nidelet S, Fellous S. Genetic independence between traits separated by metamorphosis is widespread but varies with biological function. Proc Biol Sci 2023; 290:20231784. [PMID: 37935368 PMCID: PMC10645066 DOI: 10.1098/rspb.2023.1784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 10/06/2023] [Indexed: 11/09/2023] Open
Abstract
Why is metamorphosis so pervasive? Does it facilitate the independent (micro)evolution of quantitative traits in distinct life stages, similarly to how it enables some limbs and organs to develop at specific life stages? We tested this hypothesis by measuring the expression of 6400 genes in 41 Drosophila melanogaster inbred lines at larval and adult stages. Only 30% of the genes showed significant genetic correlations between larval and adult expression. By contrast, 46% of the traits showed some level of genetic independence between stages. Gene ontology terms enrichment revealed that across stages correlated traits were often involved in proteins synthesis, insecticide resistance and innate immunity, while a vast number of genes expression traits associated with energy metabolism were independent between life stages. We compared our results to a similar case: genetic constraints between males and females in gonochoric species (i.e. sexual antagonism). We expected selection for the separation between males and females to be higher than between juvenile and adult functions, as gonochorism is a more common strategy in the animal kingdom than metamorphosis. Surprisingly, we found that inter-stage constraints were lower than inter-sexual genetic constraints. Overall, our results show that metamorphosis enables a large part of the transcriptome to evolve independently at different life stages.
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Affiliation(s)
- Julie M. Collet
- CBGP, Univ Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France
| | - Sabine Nidelet
- CBGP, Univ Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France
| | - Simon Fellous
- CBGP, Univ Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France
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Felmy A, Streiff AB, Jokela J. Propensity for selfing varies within a population of hermaphroditic snails: coexistence of selfers, outcrossers and mixed-mating individuals. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230532. [PMID: 37800152 PMCID: PMC10548103 DOI: 10.1098/rsos.230532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Accepted: 09/05/2023] [Indexed: 10/07/2023]
Abstract
To understand mating-system evolution in self-compatible hermaphrodites, variation in selfing rates is highly relevant. Empirical studies are rarely designed to capture variation between individuals, instead often comparing species and populations. Yet, evolution primarily occurs within populations, rendering among-individual variation essential. Observed individual selfing rates depend on the environment (e.g. differences in mate availability) and individuals' propensity for selfing. We quantified individual variation in selfing propensity in the snail Radix balthica by conducting laboratory mating trials that manipulated mate availability (low versus moderate) and estimating selfing rates from progeny arrays. We also measured female lifetime fitness. We found substantial among-individual variation in selfing propensity, including pure selfers (32%), pure outcrossers (31%) and mixed-mating individuals that selfed and outcrossed (37%). Experimental levels of mate availability did not significantly affect selfing rates. Selfers had reduced female liftetime fitness. Our results show that the propensity for selfing can differ considerably among individuals, with similar proportions of selfers, outcrossers and mixed maters. As mate availability did not affect selfing, our 'moderate' experimental level of mate availability might still have been too low to prompt selfers to outcross. This and the observed fitness differences also cautiously suggest that investigating the heritability of selfing propensities might be worthwhile in this population.
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Affiliation(s)
- Anja Felmy
- Department of Biology, Aquatic Ecology Unit, Lund University, 22362 Lund, Sweden
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- ETH Zurich, D-USYS, Institute of Integrative Biology, 8092 Zürich, Switzerland
| | - Alena B. Streiff
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- ETH Zurich, D-USYS, Institute of Integrative Biology, 8092 Zürich, Switzerland
| | - Jukka Jokela
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- ETH Zurich, D-USYS, Institute of Integrative Biology, 8092 Zürich, Switzerland
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Henshaw JM, Bittlingmaier M, Schärer L. Hermaphroditic origins of anisogamy. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220283. [PMID: 36934747 PMCID: PMC10024982 DOI: 10.1098/rstb.2022.0283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 11/23/2022] [Indexed: 03/21/2023] Open
Abstract
Anisogamy-the size dimorphism of gametes-is the defining difference between the male and female sexual strategies. Game-theoretic thinking led to the first convincing explanation for the evolutionary origins of anisogamy in the 1970s. Since then, formal game-theoretic models have continued to refine our understanding of when and why anisogamy should evolve. Such models typically presume that the earliest anisogamous organisms had separate sexes. However, in most taxa, there is no empirical evidence to support this assumption. Here, we present a model of the coevolution of gamete size and sex allocation, which allows for anisogamy to emerge alongside either hermaphroditism or separate sexes. We show that hermaphroditic anisogamy can evolve directly from isogamous ancestors when the average size of spawning groups is small and fertilization is relatively efficient. Sex allocation under hermaphroditism becomes increasingly female-biased as group size decreases and the degree of anisogamy increases. When spawning groups are very small, our model also predicts the existence of complex isogamous organisms in which individuals allocate resources equally to two large gamete types. We discuss common, but potentially unwarranted, assumptions in the literature that could be relaxed in future models. This article is part of the theme issue 'Half a century of evolutionary games: a synthesis of theory, application and future directions'.
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Affiliation(s)
- Jonathan M. Henshaw
- Institute of Biology I, University of Freiburg, Hauptstraße 1, D-79104 Freiburg, Germany
| | - Markus Bittlingmaier
- Institute of Biology I, University of Freiburg, Hauptstraße 1, D-79104 Freiburg, Germany
- Theoretical and Experimental Ecology Station, CNRS, 2 route du CNRS, 09200 Moulis, France
| | - Lukas Schärer
- Zoological Institute, Department of Environmental Sciences, University of Basel, Basel CH-4051, Switzerland
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McLaughlin JF, Aguilar C, Bernstein JM, Navia-Gine WG, Cueto-Aparicio LE, Alarcon AC, Alarcon BD, Collier R, Takyar A, Vong SJ, López-Chong OG, Driver R, Loaiza JR, De León LF, Saltonstall K, Lipshutz SE, Arcila D, Brock KM, Miller MJ. Comparative phylogeography reveals widespread cryptic diversity driven by ecology in Panamanian birds. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023. [PMID: 36993716 DOI: 10.1101/2023.01.26.525769] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
UNLABELLED Widespread species often harbor unrecognized genetic diversity, and investigating the factors associated with such cryptic variation can help us better understand the forces driving diversification. Here, we identify potential cryptic species based on a comprehensive dataset of COI mitochondrial DNA barcodes from 2,333 individual Panamanian birds across 429 species, representing 391 (59%) of the 659 resident landbird species of the country, as well as opportunistically sampled waterbirds. We complement this dataset with additional publicly available mitochondrial loci, such as ND2 and cytochrome b, obtained from whole mitochondrial genomes from 20 taxa. Using barcode identification numbers (BINs), we find putative cryptic species in 19% of landbird species, highlighting hidden diversity in the relatively well-described avifauna of Panama. Whereas some of these mitochondrial divergence events corresponded with recognized geographic features that likely isolated populations, such as the Cordillera Central highlands, the majority (74%) of lowland splits were between eastern and western populations. The timing of these splits are not temporally coincident across taxa, suggesting that historical events, such as the formation of the Isthmus of Panama and Pleistocene climatic cycles, were not the primary drivers of cryptic diversification. Rather, we observed that forest species, understory species, insectivores, and strongly territorial species-all traits associated with lower dispersal ability-were all more likely to have multiple BINs in Panama, suggesting strong ecological associations with cryptic divergence. Additionally, hand-wing index, a proxy for dispersal capability, was significantly lower in species with multiple BINs, indicating that dispersal ability plays an important role in generating diversity in Neotropical birds. Together, these results underscore the need for evolutionary studies of tropical bird communities to consider ecological factors along with geographic explanations, and that even in areas with well-known avifauna, avian diversity may be substantially underestimated. LAY SUMMARY - What factors are common among bird species with cryptic diversity in Panama? What role do geography, ecology, phylogeographic history, and other factors play in generating bird diversity?- 19% of widely-sampled bird species form two or more distinct DNA barcode clades, suggesting widespread unrecognized diversity.- Traits associated with reduced dispersal ability, such as use of forest understory, high territoriality, low hand-wing index, and insectivory, were more common in taxa with cryptic diversity. Filogeografía comparada revela amplia diversidad críptica causada por la ecología en las aves de Panamá. RESUMEN Especies extendidas frecuentemente tiene diversidad genética no reconocida, y investigando los factores asociados con esta variación críptica puede ayudarnos a entender las fuerzas que impulsan la diversificación. Aquí, identificamos especies crípticas potenciales basadas en un conjunto de datos de códigos de barras de ADN mitocondrial de 2,333 individuos de aves de Panama en 429 especies, representando 391 (59%) de las 659 especies de aves terrestres residentes del país, además de algunas aves acuáticas muestreada de manera oportunista. Adicionalmente, complementamos estos datos con secuencias mitocondriales disponibles públicamente de otros loci, tal como ND2 o citocroma b, obtenidos de los genomas mitocondriales completos de 20 taxones. Utilizando los números de identificación de código de barras (en ingles: BINs), un sistema taxonómico numérico que proporcina una estimación imparcial de la diversidad potencial a nivel de especie, encontramos especies crípticas putativas en 19% de las especies de aves terrestres, lo que destaca la diversidad oculta en la avifauna bien descrita de Panamá. Aunque algunos de estos eventos de divergencia conciden con características geográficas que probablemente aislaron las poblaciones, la mayoría (74%) de la divergencia en las tierras bajas se encuentra entre las poblaciones orientales y occidentales. El tiempo de esta divergencia no coincidió entre los taxones, sugiriendo que eventos históricos tales como la formación del Istmo de Panamá y los ciclos climáticos del pleistoceno, no fueron los principales impulsores de la especiación. En cambio, observamos asociaciones fuertes entre las características ecológicas y la divergencia mitocondriale: las especies del bosque, sotobosque, con una dieta insectívora, y con territorialidad fuerte mostraton múltiple BINs probables. Adicionalmente, el índice mano-ala, que está asociado a la capacidad de dispersión, fue significativamente menor en las especies con BINs multiples, sugiriendo que la capacidad de dispersión tiene un rol importamente en la generación de la diversidad de las aves neotropicales. Estos resultos demonstran la necesidad de que estudios evolutivos de las comunidades de aves tropicales consideren los factores ecológicos en conjunto con las explicaciones geográficos. Palabras clave: biodiversidad tropical, biogeografía, códigos de barras, dispersión, especies crípticas.
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Olsen KC, Levitan DR. Interpopulation variation in inbreeding is primarily driven by tolerance of mating with relatives in a spermcasting invertebrate. J Evol Biol 2023; 36:95-108. [PMID: 36420993 PMCID: PMC10098478 DOI: 10.1111/jeb.14125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 10/19/2022] [Accepted: 10/24/2022] [Indexed: 11/25/2022]
Abstract
The degree to which individuals inbreed is a fundamental aspect of population biology shaped by both passive and active processes. Yet, the relative influences of random and non-random mating on the overall magnitude of inbreeding are not well characterized for many taxa. We quantified variation in inbreeding among qualitatively accessible and isolated populations of a sessile marine invertebrate (the colonial ascidian Lissoclinum verrilli) in which hermaphroditic colonies cast sperm into the water column for subsequent uptake and internal fertilization. We compared estimates of inbreeding to simulations predicting random mating within sites to evaluate if levels of inbreeding were (1) less than expected because of active attempts to limit inbreeding, (2) as predicted by genetic subdivision and passive inbreeding tolerance, or (3) greater than simulations due to active attempts to promote inbreeding via self-fertilization or a preference for related mates. We found evidence of restricted gene flow and significant differences in the genetic diversity of L. verrilli colonies among sites, indicating that on average colonies were weakly related in accessible locations, but their levels of relatedness matched that of first cousins or half-siblings on isolated substrates. Irrespective of population size, progeny arrays revealed variation in the magnitude of inbreeding across sites that tracked with the mean relatedness of conspecifics. Biparental reproduction was confirmed in most offspring (86%) and estimates of total inbreeding largely overlapped with simulations of random mating, suggesting that interpopulation variation in mother-offspring resemblance was primarily due to genetic subdivision and passive tolerance of related mates. Our results highlight the influence of demographic isolation on the genetic composition of populations, and support theory predicting that tolerance of biparental inbreeding, even when mates are closely related, may be favoured under a broad set of ecological and evolutionary conditions.
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Affiliation(s)
- Kevin C Olsen
- Department of Biological Science, Florida State University, Tallahassee, Florida, USA
| | - Don R Levitan
- Department of Biological Science, Florida State University, Tallahassee, Florida, USA
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7
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Martinossi-Allibert I, Ament-Velásquez SL, Saupe SJ, Johannesson H. To self or not to self? Absence of mate choice despite costly outcrossing in the fungus Podospora anserina. J Evol Biol 2023; 36:238-250. [PMID: 36263943 PMCID: PMC10092876 DOI: 10.1111/jeb.14108] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 09/16/2022] [Accepted: 09/20/2022] [Indexed: 01/11/2023]
Abstract
Fungi have a large potential for flexibility in their mode of sexual reproduction, resulting in mating systems ranging from haploid selfing to outcrossing. However, we know little about which mating strategies are used in nature, and why, even in well-studied model organisms. Here, we explored the fitness consequences of alternative mating strategies in the ascomycete fungus Podospora anserina. We measured and compared fitness proxies of nine genotypes in either diploid selfing or outcrossing events, over two generations, and with or without environmental stress. We showed that fitness was consistently lower in outcrossing events, irrespective of the environment. The cost of outcrossing was partly attributed to non-self recognition genes with pleiotropic effects on fertility. We then predicted that when presented with options to either self or outcross, individuals would perform mate choice in favour of the reproductive strategy that yields higher fitness. Contrary to our prediction, individuals did not seem to avoid outcrossing when a choice was offered, in spite of the fitness cost incurred. Our results suggest that, although functionally diploid, P. anserina does not benefit from outcrossing in most cases. We outline different explanations for the apparent lack of mate choice in face of high fitness costs associated with outcrossing, including a new perspective on the pleiotropic effect of non-self recognition genes.
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Affiliation(s)
- Ivain Martinossi-Allibert
- Systematic Biology, Department of Organismal Biology, Uppsala University, Uppsala, Sweden.,Institut de Biochimie et de Génétique Cellulaire, UMR 5095 CNRS, Université de Bordeaux, Bordeaux CEDEX, France.,Department of Biology, Realfagbygget, Norwegian University of Science and Technology, Trondheim, Norway
| | | | - Sven J Saupe
- Institut de Biochimie et de Génétique Cellulaire, UMR 5095 CNRS, Université de Bordeaux, Bordeaux CEDEX, France
| | - Hanna Johannesson
- Systematic Biology, Department of Organismal Biology, Uppsala University, Uppsala, Sweden
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Díaz-Martínez JP, Mejía-Gutiérrez LM, Islas-Villanueva V, Benítez-Villalobos F. Trioecy is maintained as a time-stable mating system in the pink sea urchin Toxopneustes roseus from the Mexican Pacific. Sci Rep 2022; 12:21408. [PMID: 36496463 PMCID: PMC9741619 DOI: 10.1038/s41598-022-26059-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 12/08/2022] [Indexed: 12/13/2022] Open
Abstract
Trioecy is a sexual system that consists of the co-occurrence of females, males and hermaphrodites in a population and is common in plants; however, in animals it is uncommon and poorly understood. In echinoderms, trioecy had never been recorded until now. Frequencies of females, males, and hermaphrodites were evaluated and gametogenic development was histologically characterized in a population of Toxopneustes roseus inhabiting the Mexican Pacific. Trioecy in this population is functional and temporally stable, since the three sexes coexisted in each sampling month. The hermaphrodites presented similar gametogenic development as the females and males and participated during the spawning season, contributing to the population's reproductive process. Trioecy is considered an evolutionarily transitory state, and it is extremely difficult to explain its presence in a species. We hypothesize that continuous ocean warming represents a threat to the survival of this population of T. roseus, since its early developmental stages, which represent a population bottleneck, are more vulnerable to high temperatures than other sea urchins inhabiting the area, while its population density is significantly lower. These conditions generate a strongly stressed environment, which is the determining factor that maintains the stability of trioecy in the species in which it has been studied.
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Affiliation(s)
- Julia Patricia Díaz-Martínez
- Programa de Posgrado en Ecología Marina, División de Estudios de Posgrado, Universidad del Mar Campus Puerto Ángel, Cd. Universitaria S/N, 70902, Oaxaca, Mexico
| | - Leobarda Margarita Mejía-Gutiérrez
- Programa de Posgrado en Ecología Marina, División de Estudios de Posgrado, Universidad del Mar Campus Puerto Ángel, Cd. Universitaria S/N, 70902, Oaxaca, Mexico
| | - Valentina Islas-Villanueva
- Consejo Nacional de Ciencia y Tecnología (CONACYT), Av. de los Insurgentes Sur 1582, 03940, Mexico, Mexico
- Instituto de Genética, Universidad del Mar Campus Puerto Ángel, Cd. Universitaria S/N, 70902, Oaxaca, Mexico
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Jarvis GC, White CR, Marshall DJ. Macroevolutionary patterns in marine hermaphroditism. Evolution 2022; 76:3014-3025. [PMID: 36199199 PMCID: PMC10091813 DOI: 10.1111/evo.14639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 08/08/2022] [Accepted: 08/23/2022] [Indexed: 01/22/2023]
Abstract
Most plants and many animals are hermaphroditic; whether the same forces are responsible for hermaphroditism in both groups is unclear. The well-established drivers of hermaphroditism in plants (e.g., seed dispersal potential, pollination mode) have analogues in animals (e.g., larval dispersal potential, fertilization mode), allowing us to test the generality of the proposed drivers of hermaphroditism across both groups. Here, we test these theories for 1153 species of marine invertebrates, from three phyla. Species with either internal fertilization, restricted offspring dispersal, or small body sizes are more likely to be hermaphroditic than species that are external fertilizers, planktonic developers, or larger. Plants and animals show different biogeographical patterns, however: animals are less likely to be hermaphroditic at higher latitudes-the opposite to the trend in plants. Overall, our results suggest that similar forces, namely, competition among offspring or gametes, shape the evolution of hermaphroditism across plants and three invertebrate phyla.
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Affiliation(s)
- George C. Jarvis
- School of Biological Sciences/Centre for Geometric BiologyMonash UniversityMelbourneVIC 3800Australia
| | - Craig R. White
- School of Biological Sciences/Centre for Geometric BiologyMonash UniversityMelbourneVIC 3800Australia
| | - Dustin J. Marshall
- School of Biological Sciences/Centre for Geometric BiologyMonash UniversityMelbourneVIC 3800Australia
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10
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Blüml C, Ramm SA, van Benthem KJ, Wittmann MJ. Waiting for love but not forever: Modeling the evolution of waiting time to selfing in hermaphrodites. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.1002475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Although mixed mating systems involving both selfing and outcrossing are fairly common in hermaphrodites, the mechanisms maintaining mixed mating are still unknown in many cases. In some species, individuals that have not yet found a mating partner delay self-fertilization for some time. This “waiting time” to selfing (WT) can exhibit heritable variation between individuals and is subject to two opposing selection pressures: waiting longer increases the density-dependent probability to encounter a mate within that time and thereby the chance to avoid inbreeding depression (ID) in offspring, but also increases the risk of dying before reproduction. It has long been hypothesized that fluctuations in population density and thus mate availability can lead to stable intermediate WTs, but to our knowledge there are so far no quantitative models that also take into account the joint evolutionary dynamics of ID. We use an individual-based model and a mathematical approximation to explore how delayed selfing evolves in response to density and density fluctuations. We find that at high density, when individuals meet often, WT evolution is dominated by genetic drift; at intermediate densities, strong ID causes WT to increase; and at low densities, ID is purged and WT approaches zero. Positive feedback loops drive the system to either complete selfing or complete outcrossing. Fluctuating density can slow down convergence to these alternative stable states. However, mixed mating, in the sense of either a stable polymorphism in WT, or stable intermediate waiting times, was never observed. Thus, additional factors need to be explored to explain the persistence of delayed selfing.
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11
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Taraporevala NF, Lesoway MP, Goodheart JA, Lyons DC. Precocious Sperm Exchange in the Simultaneously Hermaphroditic Nudibranch, Berghia stephanieae. Integr Org Biol 2022; 4:obac030. [PMID: 36089995 PMCID: PMC9449679 DOI: 10.1093/iob/obac034] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 06/10/2022] [Accepted: 07/28/2022] [Indexed: 11/15/2022] Open
Abstract
Sexual systems vary greatly across molluscs. This diversity includes simultaneous hermaphroditism, with both sexes functional at the same time. Most nudibranch molluscs are thought to be simultaneous hermaphrodites, but detailed studies of reproductive development and timing remain rare as most species cannot be cultured in the lab. The aeolid nudibranch, Berghia stephanieae, is one such species that can be cultured through multiple generations on the benchtop. We studied B. stephanieae reproductive timing to establish when animals first exchange sperm and how long sperm can be stored. We isolated age- and size-matched individuals at sequential timepoints to learn how early individuals can exchange sperm. Individuals isolated at 10 weeks post initial feeding (wpf; ∼13 weeks postlaying [wpl]) can produce fertilized eggs. This is 6 weeks before animals first lay egg masses, indicating that sperm exchange occurs well before individuals are capable of laying eggs. Our results indicate that male gonads become functional for animals between 6 mm (∼6 wpf, ∼9 wpl) and 9 mm (∼12 wpf, ∼15 wpl) in length. That is much smaller (and sooner) than the size (and age) of individuals at first laying (12–19 mm; ∼16 wpf, ∼19 wpl), indicating that male and female functions do not develop simultaneously. We also tracked the number of fertilized eggs in each egg mass, which remained steady for the first 10–15 egg masses, followed by a decline to near-to-no fertilization. This dataset provides insights into the precise timing of the onset of functionality of the male and female reproductive systems in B. stephanieae. These data contribute to a broader understanding of reproductive development and the potential for understanding the evolution of diverse sexual systems in molluscs.
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Affiliation(s)
- Neville F Taraporevala
- Scripps Institution of Oceanography, University of California San Diego , 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Maryna P Lesoway
- Scripps Institution of Oceanography, University of California San Diego , 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Jessica A Goodheart
- Scripps Institution of Oceanography, University of California San Diego , 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Deirdre C Lyons
- Scripps Institution of Oceanography, University of California San Diego , 9500 Gilman Drive, La Jolla, CA 92093, USA
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12
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Evolution of sexual systems, sex chromosomes and sex-linked gene transcription in flatworms and roundworms. Nat Commun 2022; 13:3239. [PMID: 35688815 PMCID: PMC9187692 DOI: 10.1038/s41467-022-30578-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 05/06/2022] [Indexed: 12/02/2022] Open
Abstract
Many species with separate male and female individuals (termed ‘gonochorism’ in animals) have sex-linked genome regions. Here, we investigate evolutionary changes when genome regions become completely sex-linked, by analyses of multiple species of flatworms (Platyhelminthes; among which schistosomes recently evolved gonochorism from ancestral hermaphroditism), and roundworms (Nematoda) which have undergone independent translocations of different autosomes. Although neither the evolution of gonochorism nor translocations fusing ancestrally autosomal regions to sex chromosomes causes inevitable loss of recombination, we document that formerly recombining regions show genomic signatures of recombination suppression in both taxa, and become strongly genetically degenerated, with a loss of most genes. Comparisons with hermaphroditic flatworm transcriptomes show masculinisation and some defeminisation in schistosome gonad gene expression. We also find evidence that evolution of sex-linkage in nematodes is accompanied by transcriptional changes and dosage compensation. Our analyses also identify sex-linked genes that could assist future research aimed at controlling some of these important parasites. Transitions between hermaphroditic and separate sexes are relatively understudied in animals compared to pants. Here, Wang et al. reconstruct the evolution of separate sexes in the flatworms and complex changes of sex chromosomes in the roundworms.
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13
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Pla S, Benvenuto C, Capellini I, Piferrer F. Switches, stability and reversals in the evolutionary history of sexual systems in fish. Nat Commun 2022; 13:3029. [PMID: 35637181 PMCID: PMC9151764 DOI: 10.1038/s41467-022-30419-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Accepted: 04/29/2022] [Indexed: 11/09/2022] Open
Abstract
Sexual systems are highly diverse and have profound consequences for population dynamics and resilience. Yet, little is known about how they evolved. Using phylogenetic Bayesian modelling and a sample of 4614 species, we show that gonochorism is the likely ancestral condition in teleost fish. While all hermaphroditic forms revert quickly to gonochorism, protogyny and simultaneous hermaphroditism are evolutionarily more stable than protandry. In line with theoretical expectations, simultaneous hermaphroditism does not evolve directly from gonochorism but can evolve slowly from sequential hermaphroditism, particularly protandry. We find support for the predictions from life history theory that protogynous, but not protandrous, species live longer than gonochoristic species and invest the least in male gonad mass. The distribution of teleosts' sexual systems on the tree of life does not seem to reflect just adaptive predictions, suggesting that adaptations alone may not fully explain why some sexual forms evolve in some taxa but not others (Williams' paradox). We propose that future studies should incorporate mating systems, spawning behaviours, and the diversity of sex determining mechanisms. Some of the latter might constrain the evolution of hermaphroditism, while the non-duality of the embryological origin of teleost gonads might explain why protogyny predominates over protandry in teleosts.
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Affiliation(s)
- Susanna Pla
- Institut de Ciències del Mar, Spanish National Research Council (CSIC), Barcelona, Spain
| | - Chiara Benvenuto
- School of Science, Engineering and Environment, University of Salford, Salford, UK
| | | | - Francesc Piferrer
- Institut de Ciències del Mar, Spanish National Research Council (CSIC), Barcelona, Spain.
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14
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Carey SB, Lovell JT, Jenkins J, Leebens-Mack J, Schmutz J, Wilson MA, Harkess A. Representing sex chromosomes in genome assemblies. CELL GENOMICS 2022; 2. [PMID: 35720975 PMCID: PMC9205529 DOI: 10.1016/j.xgen.2022.100132] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Sex chromosomes have evolved hundreds of independent times across eukaryotes. As genome sequencing, assembly, and scaffolding techniques rapidly improve, it is now feasible to build fully phased sex chromosome assemblies. Despite technological advances enabling phased assembly of whole chromosomes, there are currently no standards for representing sex chromosomes when publicly releasing a genome. Furthermore, most computational analysis tools are unable to efficiently investigate their unique biology relative to autosomes. We discuss a diversity of sex chromosome systems and consider the challenges of representing sex chromosome pairs in genome assemblies. By addressing these issues now as technologies for full phasing of chromosomal assemblies are maturing, we can collectively ensure that future genome analysis toolkits can be broadly applied to all eukaryotes with diverse types of sex chromosome systems. Here we provide best practice guidelines for presenting a genome assembly that contains sex chromosomes. These guidelines can also be applied to other non-recombining genomic regions, such as S-loci in plants and mating-type loci in fungi and algae.
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Affiliation(s)
- Sarah B Carey
- Department of Crop, Soil, and Environmental Sciences, Auburn University, Auburn, AL 36849, USA.,HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA
| | - John T Lovell
- HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA
| | - Jerry Jenkins
- HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA
| | - Jim Leebens-Mack
- Department of Plant Biology, University of Georgia, Athens, GA 30602, USA
| | - Jeremy Schmutz
- HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA.,US Department of Energy Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Melissa A Wilson
- School of Life Sciences, Center for Evolution and Medicine, The Biodesign Institute, Arizona State University, Tempe, AZ 85287, USA
| | - Alex Harkess
- Department of Crop, Soil, and Environmental Sciences, Auburn University, Auburn, AL 36849, USA.,HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA
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15
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Detection of sex in adults and larvae of Leptinotarsa decemlineata on principle of copy number variation. Sci Rep 2022; 12:4602. [PMID: 35301399 PMCID: PMC8931150 DOI: 10.1038/s41598-022-08642-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 03/10/2022] [Indexed: 12/02/2022] Open
Abstract
The identification of sex in larvae of insects is usually challenging or even impossible, while in adults the sexual dimorphism is usually evident. Here, we used copy number analysis to develop a method of sex detection in Colorado potato beetle (Leptinotarsa decemlineata), which has an X0 sex determination system. The X linked gene LdVssc and autosomal gene LdUBE3B were identified as appropriate target and reference loci, respectively. The copy numbers (CNV) of LdVssc in males and females were estimated using standard droplet digital PCR (ddPCR) and real-time PCR (qPCR). With both methods, CNVs were bimodally distributed (BAddPCR = 0.709 and BAqPCR = 0.683) with 100% ability to distinguish females from males. The use of qPCR-based sex detection in a broad collection of 448 random CPB adults showed a perfect association (Phi = 1.0, p < 0.05) with the true sexes of adults, with mean CNV in females of 2.032 (SD = 0.227) and 0.989 in males (SD = 0.147). In the collection of 50 random 4th instar larvae, 27 females and 23 males were identified, consistent with the expected 1:1 sex ratio (p = 0.689). The method is suitable for sexing in all stages of ontogenesis. The optimal cost-effective application of the method in large populations requires the DNA extraction using CTAB, the qPCR assay in one biological replicate and three technical replicates of each marker, and the use of one randomly chosen male per run to calibrate calculation of CNV.
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16
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Shi Y, Yao G, Zhang H, Jia H, Xiong P, He M. Proteome and Transcriptome Analysis of Gonads Reveals Intersex in Gigantidas haimaensis. BMC Genomics 2022; 23:174. [PMID: 35240981 PMCID: PMC8892766 DOI: 10.1186/s12864-022-08407-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 02/22/2022] [Indexed: 11/19/2022] Open
Abstract
Sex has proven to be one of the most intriguing areas of research across evolution, development, and ecology. Intersex or sex change occurs frequently in molluscs. The deep-sea mussel Gigantidas haimaensis often dominates within Haima cold seep ecosystems, but details of their reproduction remain unknown. Herein, we conducted a combined proteomic and transcriptomic analysis of G. haimaensis gonads to provide a systematic understanding of sexual development in deep-sea bivalves. A total of 2,452 out of 42,238 genes (5.81%) and 288 out of 7,089 proteins (4.06%) were significantly differentially expressed between ovaries and testes with a false discovery rate (FDR) <0.05. Candidate genes involved in sexual development were identified; among 12 differentially expressed genes between sexes, four ovary-biased genes (β-catenin, fem-1, forkhead box L2 and membrane progestin receptor α) were expressed significantly higher in males than females. Combining histological characteristics, we speculate that the males maybe intersex undergoing sex change, and implied that these genes may be involved in the process of male testis converting into female gonads in G. haimaensis. The results suggest that this adaptation may be based on local environmental factors, sedentary lifestyles, and patchy distribution, and sex change may facilitate adaptation to a changing environment and expansion of the population. The findings provide a valuable genetic resource to better understand the mechanisms of sex change and survival strategies in deep-sea bivalves.
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Affiliation(s)
- Yu Shi
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou, 510301, China.,Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China
| | - Gaoyou Yao
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou, 510301, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Hua Zhang
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou, 510301, China.,Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China
| | - Huixia Jia
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou, 510301, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Panpan Xiong
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou, 510301, China.,University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Maoxian He
- CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou, 510301, China. .,Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou, 511458, China.
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17
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Brand JN, Harmon LJ, Schärer L. Frequent origins of traumatic insemination involve convergent shifts in sperm and genital morphology. Evol Lett 2022; 6:63-82. [PMID: 35127138 PMCID: PMC8802240 DOI: 10.1002/evl3.268] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 11/30/2021] [Accepted: 12/02/2021] [Indexed: 12/18/2022] Open
Abstract
Traumatic insemination is a mating behavior during which the (sperm) donor uses a traumatic intromittent organ to inject an ejaculate through the epidermis of the (sperm) recipient, thereby frequently circumventing the female genitalia. Traumatic insemination occurs widely across animals, but the frequency of its evolution, the intermediate stages via which it originates, and the morphological changes that such shifts involve remain poorly understood. Based on observations in 145 species of the free-living flatworm genus Macrostomum, we identify at least nine independent evolutionary origins of traumatic insemination from reciprocal copulation, but no clear indication of reversals. These origins involve convergent shifts in multivariate morphospace of male and female reproductive traits, suggesting that traumatic insemination has a canalizing effect on morphology. We also observed sperm in both the sperm receiving organ and within the body tissue of two species. These species had intermediate trait values indicating that traumatic insemination evolves through initial internal wounding during copulation. Finally, signatures of male-female coevolution of genitalia across the genus indicate that sexual selection and sexual conflict drive the evolution of traumatic insemination, because it allows donors to bypass postcopulatory control mechanisms of recipients.
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Affiliation(s)
- Jeremias N. Brand
- Department of Environmental Sciences, Zoological InstituteUniversity of BaselBaselCH‐4051Switzerland
- Department of Tissue Dynamics and RegenerationMax Planck Institute for Biophysical ChemistryGöttingenDE‐37077Germany
| | - Luke J. Harmon
- Department of Biological SciencesUniversity of IdahoMoscowIdaho83843
| | - Lukas Schärer
- Department of Environmental Sciences, Zoological InstituteUniversity of BaselBaselCH‐4051Switzerland
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18
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Alves DFR, Barros-Alves SP, Almeida AC, Costa RC. Sex change and reproductive output of the protandric shrimp Merguia rhizophorae (Rathbun, 1900) (Decapoda, Merguiidae). J NAT HIST 2022. [DOI: 10.1080/00222933.2021.2019339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Douglas Fernandes Rodrigues Alves
- Laboratório de Ecologia de Ecossistemas Aquáticos (LEEA), Universidade Federal de Uberlândia (UFU), Programa de Pós-Graduação em Ecologia e Conservação de Recursos Naturais (PPGECO), Uberlândia, Minas Gerais, Brazil
| | - S. P. Barros-Alves
- Departamento de Ciências Agrárias e Naturais (DECAN), Universidade do Estado de Minas Gerais (UEMG), Unidade de Ituiutaba, Ituiutaba, Minas Gerais, Brazil
| | - A. C. Almeida
- Laboratório de Ecologia de Ecossistemas Aquáticos (LEEA), Universidade Federal de Uberlândia (UFU), Programa de Pós-Graduação em Ecologia e Conservação de Recursos Naturais (PPGECO), Uberlândia, Minas Gerais, Brazil
| | - R. C. Costa
- Laboratory of Biology and Ecology of Marine and Freshwater Shrimps (LABCAM), Universidade Estadual Paulista (UNESP), Faculdade de Ciências, Departamento de Ciências Biológicas, Bauru, São Paulo, Brazil
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19
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Hart MW, Guerra VI, Allen JD, Byrne M. Cloning and Selfing Affect Population Genetic Variation in Simulations of Outcrossing, Sexual Sea Stars. THE BIOLOGICAL BULLETIN 2021; 241:286-302. [PMID: 35015625 DOI: 10.1086/717293] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
AbstractMany sea stars are well known for facultative or obligate asexual reproduction in both the adult and larval life-cycle stages. Some species and lineages are also capable of facultative or obligate hermaphroditic reproduction with self-fertilization. However, models of population genetic variation and empirical analyses of genetic data typically assume only sexual reproduction and outcrossing. A recent reanalysis of previously published empirical data (microsatellite genotypes) from two studies of one of the most well-known sea star species (the crown-of-thorns sea star; Acanthaster sp.) concluded that cloning and self-fertilization in that species are rare and contribute little to patterns of population genetic variation. Here we reconsider that conclusion by simulating the contribution of cloning and selfing to genetic variation in a series of models of sea star demography. Simulated variation in two simple models (analogous to previous analyses of empirical data) was consistent with high rates of cloning or selfing or both. More realistic scenarios that characterize population flux in sea stars of ecological significance, including outbreaks of crown-of-thorns sea stars that devastate coral reefs, invasions by Asterias amurensis, and epizootics of sea star wasting disease that kill Pisaster ochraceus, also showed significant but smaller effects of cloning and selfing on variation within subpopulations and differentiation between subpopulations. Future models or analyses of genetic variation in similar study systems might benefit from simulation modeling to characterize possible contributions of cloning or selfing to genetic variation in population samples or to understand the limits on inferring the effects of cloning or selfing in nature.
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20
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Trickovic B, Glémin S. Establishment of local adaptation in partly self-fertilizing populations. Genetics 2021; 220:6428547. [PMID: 34791199 PMCID: PMC9208650 DOI: 10.1093/genetics/iyab201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 10/21/2021] [Indexed: 11/12/2022] Open
Abstract
Populations often inhabit multiple ecological patches and thus experience divergent selection, which can lead to local adaptation if migration is not strong enough to swamp locally adapted alleles. Conditions for the establishment of a locally advantageous allele have been studied in randomly mating populations. However, many species reproduce, at least partially, through self-fertilization, and how selfing affects local adaptation remains unclear and debated. Using a two-patch branching process formalism, we obtained a closed-form approximation under weak selection for the probability of establishment of a locally advantageous allele (P) for arbitrary selfing rate and dominance level, where selection is allowed to act on viability or fecundity, and migration can occur via seed or pollen dispersal. This solution is compared to diffusion approximation and used to investigate the consequences of a shift in a mating system on P, and the establishment of protected polymorphism. We find that selfing can either increase or decrease P, depending on the patterns of dominance in the two patches, and has conflicting effects on local adaptation. Globally, selfing favors local adaptation when locally advantageous alleles are (partially) recessive, when selection between patches is asymmetrical and when migration occurs through pollen rather than seed dispersal. These results establish a rigorous theoretical background to study heterogeneous selection and local adaptation in partially selfing species.
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Affiliation(s)
- Bogi Trickovic
- Center for Mechanisms of Evolution, Arizona State University, AZ 85281, Tempe, United States of America
| | - Sylvain Glémin
- University of Rennes, CNRS, ECOBIO [(Ecosystèmes, biodiversityé, évolution)] - UMR 6553, Rennes, France.,Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
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21
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Janicke T, Chapuis E, Meconcelli S, Bonel N, Delahaie B, David P. Environmental effects on the genetic architecture of fitness components in a simultaneous hermaphrodite. J Anim Ecol 2021; 91:124-137. [PMID: 34652857 DOI: 10.1111/1365-2656.13607] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 10/04/2021] [Indexed: 12/01/2022]
Abstract
Understanding how environmental change affects genetic variances and covariances of reproductive traits is key to formulate firm predictions on evolutionary responses. This is particularly true for sex-specific variance in reproductive success, which has been argued to affect how populations can adapt to environmental change. Our current knowledge on the impact of environmental stress on sex-specific genetic architecture of fitness components is still limited and restricted to separate-sexed organisms. However, hermaphroditism is widespread across animals and may entail interesting peculiarities with respect to genetic constraints imposed on the evolution of male and female reproduction. We explored how food restriction affects the genetic variance-covariance (G) matrix of body size and reproductive success of the simultaneously hermaphroditic freshwater snail Physa acuta. Our results provide strong evidence that the imposed environmental stress elevated the opportunity for selection in both sex functions. However, the G-matrix remained largely stable across the tested food treatments. Importantly, our results provide no support for cross-sex genetic correlations suggesting no strong evolutionary coupling of male and female reproductive traits. We discuss potential implications for the adaptation to changing environments and highlight the need for more quantitative genetic studies on male and female fitness components in simultaneous hermaphrodites.
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Affiliation(s)
- Tim Janicke
- Centre d'Écologie Fonctionnelle et Évolutive, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France.,Applied Zoology, Technical University Dresden, Dresden, Germany
| | - Elodie Chapuis
- MIVEGEC, Univ Montpellier, CNRS, IRD, Montpellier, France
| | - Stefania Meconcelli
- Centre d'Écologie Fonctionnelle et Évolutive, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France.,Department of Life Sciences and Systems Biology, Università di Torino, Torino, Italy
| | - Nicolas Bonel
- Centre d'Écologie Fonctionnelle et Évolutive, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France.,Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS-CCT-CONICET Bahía Blanca), Bahía Blanca, Argentina
| | - Boris Delahaie
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Patrice David
- Centre d'Écologie Fonctionnelle et Évolutive, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France
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22
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Against the Odds: Hybrid Zones between Mangrove Killifish Species with Different Mating Systems. Genes (Basel) 2021; 12:genes12101486. [PMID: 34680881 PMCID: PMC8535463 DOI: 10.3390/genes12101486] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 09/21/2021] [Accepted: 09/22/2021] [Indexed: 11/16/2022] Open
Abstract
Different mating systems are expected to affect the extent and direction of hybridization. Due to the different levels of sexual conflict, the weak inbreeder/strong outbreeder (WISO) hypothesis predicts that gametes from self-incompatible (SI) species should outcompete gametes from self-compatible (SC) ones. However, other factors such as timing of selfing and unilateral incompatibilities may also play a role on the direction of hybridization. In addition, differential mating opportunities provided by different mating systems are also expected to affect the direction of introgression in hybrid zones involving outcrossers and selfers. Here, we explored these hypotheses with a unique case of recent hybridization between two mangrove killifish species with different mating systems, Kryptolebias ocellatus (obligately outcrossing) and K. hermaphroditus (predominantly self-fertilizing) in two hybrid zones in southeast Brazil. Hybridization rates were relatively high (~20%), representing the first example of natural hybridization between species with different mating systems in vertebrates. All F1 individuals were sired by the selfing species. Backcrossing was small, but mostly asymmetrical with the SI parental species, suggesting pattern commonly observed in plant hybrid zones with different mating systems. Our findings shed light on how contrasting mating systems may affect the direction and extent of gene flow between sympatric species, ultimately affecting the evolution and maintenance of hybrid zones.
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23
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Meissner ST. Plant sexual reproduction: perhaps the current plant two-sex model should be replaced with three- and four-sex models? PLANT REPRODUCTION 2021; 34:175-189. [PMID: 34213647 PMCID: PMC8360875 DOI: 10.1007/s00497-021-00420-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Accepted: 06/07/2021] [Indexed: 06/12/2023]
Abstract
The two-sex model makes the assumption that there are only two sexual reproductive states: male and female. However, in land plants (embryophytes) the application of this model to the alternation of generations life cycle requires the subtle redefinition of several common terms related to sexual reproduction, which seems to obscure aspects of one or the other plant generation: For instance, the homosporous sporophytic plant is treated as being asexual, and the gametophytes of angiosperms treated like mere gametes. In contrast, the proposal is made that the sporophytes of homosporous plants are indeed sexual reproductive organisms, as are the gametophytes of heterosporous plants. This view requires the expansion of the number of sexual reproductive states we accept for these plant species; therefore, a three-sex model for homosporous plants and a four-sex model for heterosporous plants are described and then contrasted with the current two-sex model. These new models allow the use of sexual reproductive terms in a manner largely similar to that seen in animals, and may better accommodate the plant alternation of generations life cycle than does the current plant two-sex model. These new models may also help stimulate new lines of research, and examples of how they might alter our view of events in the flower, and may lead to new questions about sexual determination and differentiation, are presented. Thus it is suggested that land plant species have more than merely two sexual reproductive states and that recognition of this may promote our study and understanding of them.
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Affiliation(s)
- Scott T Meissner
- Institute of Biology, University of the Philippines Diliman, 1101, Quezon City, NCR, Philippines.
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24
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Picard MAL, Vicoso B, Bertrand S, Escriva H. Diversity of Modes of Reproduction and Sex Determination Systems in Invertebrates, and the Putative Contribution of Genetic Conflict. Genes (Basel) 2021; 12:1136. [PMID: 34440310 PMCID: PMC8391622 DOI: 10.3390/genes12081136] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 07/08/2021] [Accepted: 07/11/2021] [Indexed: 12/30/2022] Open
Abstract
About eight million animal species are estimated to live on Earth, and all except those belonging to one subphylum are invertebrates. Invertebrates are incredibly diverse in their morphologies, life histories, and in the range of the ecological niches that they occupy. A great variety of modes of reproduction and sex determination systems is also observed among them, and their mosaic-distribution across the phylogeny shows that transitions between them occur frequently and rapidly. Genetic conflict in its various forms is a long-standing theory to explain what drives those evolutionary transitions. Here, we review (1) the different modes of reproduction among invertebrate species, highlighting sexual reproduction as the probable ancestral state; (2) the paradoxical diversity of sex determination systems; (3) the different types of genetic conflicts that could drive the evolution of such different systems.
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Affiliation(s)
- Marion Anne Lise Picard
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, 66650 Banyuls-sur-Mer, France; (S.B.); (H.E.)
| | - Beatriz Vicoso
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria;
| | - Stéphanie Bertrand
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, 66650 Banyuls-sur-Mer, France; (S.B.); (H.E.)
| | - Hector Escriva
- Sorbonne Université, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, 66650 Banyuls-sur-Mer, France; (S.B.); (H.E.)
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25
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Tessens B, Monnens M, Backeljau T, Jordaens K, Van Steenkiste N, Breman FC, Smeets K, Artois T. Is ‘everything everywhere’? Unprecedented cryptic diversity in the cosmopolitan flatworm
Gyratrix hermaphroditus. ZOOL SCR 2021. [DOI: 10.1111/zsc.12507] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Bart Tessens
- Research Group Zoology: Biodiversity and Toxicology Centre for Environmental Sciences Hasselt University Diepenbeek Belgium
| | - Marlies Monnens
- Research Group Zoology: Biodiversity and Toxicology Centre for Environmental Sciences Hasselt University Diepenbeek Belgium
| | - Thierry Backeljau
- Department of Biology Evolutionary Ecology Group University of Antwerp Antwerp Belgium
- Royal Belgian Institute of Natural Sciences (RBINS: Taxonomy and Phylogeny & JEMU) Brussels Belgium
| | - Kurt Jordaens
- Royal Museum for Central Africa (RMCA: Entomology Section & JEMU) Tervuren Belgium
| | - Niels Van Steenkiste
- Research Group Zoology: Biodiversity and Toxicology Centre for Environmental Sciences Hasselt University Diepenbeek Belgium
- Departments of Botany and Zoology University of British Columbia Vancouver BC Canada
| | - Floris C. Breman
- Royal Belgian Institute of Natural Sciences (RBINS: Taxonomy and Phylogeny & JEMU) Brussels Belgium
| | - Karen Smeets
- Research Group Zoology: Biodiversity and Toxicology Centre for Environmental Sciences Hasselt University Diepenbeek Belgium
| | - Tom Artois
- Research Group Zoology: Biodiversity and Toxicology Centre for Environmental Sciences Hasselt University Diepenbeek Belgium
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Lesoway MP, Henry JQ. Retinoids promote penis development in sequentially hermaphroditic snails. Dev Biol 2021; 478:122-132. [PMID: 34224682 DOI: 10.1016/j.ydbio.2021.06.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 06/21/2021] [Accepted: 06/30/2021] [Indexed: 11/30/2022]
Abstract
Sexual systems are surprisingly diverse, considering the ubiquity of sexual reproduction. Sequential hermaphroditism, the ability of an individual to change sex, has emerged multiple times independently across the animal kingdom. In molluscs, repeated shifts between ancestrally separate sexes and hermaphroditism are generally found at the level of family and above, suggesting recruitment of deeply conserved mechanisms. Despite this, molecular mechanisms of sexual development are poorly known. In molluscs with separate sexes, endocrine disrupting toxins bind the retinoid X receptor (RXR), activating ectopic male development in females, suggesting the retinoid pathway as a candidate controlling sexual transitions in sequential hermaphrodites. We therefore tested the role of retinoic acid signaling in sequentially hermaphroditic Crepidula snails, which develop first into males, then change sex, maturing into females. We show that retinoid agonists induce precocious penis growth in juveniles and superimposition of male development in females. Combining RXR antagonists with retinoid agonists significantly reduces penis length in induced juveniles, while similar treatments using retinoic acid receptor (RAR) antagonists increase penis length. Transcripts of both receptors are expressed in the induced penis. Our findings therefore show that retinoid signaling can initiate molluscan male genital development, and regulate penis length. Further, we show that retinoids induce ectopic male development in multiple Crepidula species. Species-specific influence of conspecific induction of sexual transitions correlates with responsiveness to retinoids. We propose that retinoid signaling plays a conserved role in molluscan male development, and that shifts in the timing of retinoid signaling may have been important for the origins of sequential hermaphroditism within molluscs.
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Affiliation(s)
- Maryna P Lesoway
- Department of Cell and Developmental Biology University of Illinois, 601 S Goodwin Avenue Urbana, IL, USA, 61801.
| | - Jonathan Q Henry
- Department of Cell and Developmental Biology University of Illinois, 601 S Goodwin Avenue Urbana, IL, USA, 61801
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27
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Camus C, Solas M, Martínez C, Vargas J, Garcés C, Gil-Kodaka P, Ladah LB, Serrão EA, Faugeron S. Mates Matter: Gametophyte Kinship Recognition and Inbreeding in the Giant Kelp, Macrocystis pyrifera (Laminariales, Phaeophyceae). JOURNAL OF PHYCOLOGY 2021; 57:711-725. [PMID: 33583038 DOI: 10.1111/jpy.13146] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 12/22/2020] [Accepted: 01/05/2021] [Indexed: 06/12/2023]
Abstract
Inbreeding, the mating between genetically related individuals, often results in reduced survival and fecundity of offspring, relative to outcrossing. Yet, high inbreeding rates are commonly observed in seaweeds, suggesting compensatory reproductive traits may affect the costs and benefits of the mating system. We experimentally manipulated inbreeding levels in controlled crossing experiments, using gametophytes from 19 populations of Macrocystis pyrifera along its Eastern Pacific coastal distribution (EPC). The objective was to investigate the effects of male-female kinship on female fecundity and fertility, to estimate inbreeding depression in the F1 progeny, and to assess the variability of these effects among different regions and habitats of the EPC. Results revealed that the presence and kinship of males had a significant effect on fecundity and fertility of female gametophytes. Females left alone or in the presence of sibling males express the highest gametophyte size, number, and size of oogonia, suggesting they were able to sense the presence and the identity of their mates before gamete contact. The opposite trend was observed for the production of embryos per female gametes, indicating higher costs of selfing and parthenogenesis than outcrossing on fertility. However, the increased fecundity compensated for the reduced fertility, leading to a stable overall reproductive output. Inbreeding also affected morphological traits of juvenile sporophytes, but not their heatwave tolerance. The male-female kinship effect was stronger in high-latitude populations, suggesting that females from low-latitude marginal populations might have evolved to mate with any male gamete to guarantee reproductive success.
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Affiliation(s)
- Carolina Camus
- Centro i~mar and CeBiB, Universidad de Los Lagos, Puerto Montt, Chile
| | - Maribel Solas
- Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | | | - Jaime Vargas
- Centro i~mar, Universidad de Los Lagos, Puerto Montt, Chile
| | | | | | - Lydia B Ladah
- Department of Biological Oceanography, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, México
| | | | - Sylvain Faugeron
- Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
- UMI3614 Evolutionary Biology and Ecology of Algae, CNRS, Sorbonne Université, Pontificia Universidad Católica de Chile, Universidad Austral de Chile, Roscoff, France
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28
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Three genomes in the algal genus Volvox reveal the fate of a haploid sex-determining region after a transition to homothallism. Proc Natl Acad Sci U S A 2021; 118:2100712118. [PMID: 34011609 PMCID: PMC8166075 DOI: 10.1073/pnas.2100712118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Evolutionary transitions between species with separate sexes and species in which individuals have both sex functions have wide-ranging biological implications. It is largely unknown how such transitions occur in systems with haploid male- and female-determining chromosomes in algae and bryophytes. We investigated such a transition in the algal genus Volvox by making whole-genome sequences of two closely related species, one of which is heterothallic (with distinct males and females) and the other homothallic (with only bisexual, self-compatible individuals). The heterothallic species harbors a sex-determining region (SDR), while the homothallic species retains a nearly intact female-derived SDR-like region and separate regions containing key male genes. Thus, an ancestral female has probably become homothallic by acquiring genes that confer male functions. Transitions between separate sexes (dioecy) and other mating systems are common across eukaryotes. Here, we study a change in a haploid dioecious green algal species with male- and female-determining chromosomes (U and V). The genus Volvox is an oogamous (with large, immotile female gametes and small, motile male gametes) and includes both heterothallic species (with distinct male and female genotypes, associated with a mating-type system that prevents fusion of gametes of the same sex) and homothallic species (bisexual, with the ability to self-fertilize). We date the origin of an expanded sex-determining region (SDR) in Volvox to at least 75 Mya, suggesting that homothallism represents a breakdown of dioecy (heterothallism). We investigated the involvement of the SDR of the U and V chromosomes in this transition. Using de novo whole-genome sequences, we identified a heteromorphic SDR of ca 1 Mbp in male and female genotypes of the heterothallic species Volvox reticuliferus and a homologous region (SDLR) in the closely related homothallic species Volvox africanus, which retained several different hallmark features of an SDR. The V. africanus SDLR includes a large region resembling the female SDR of the presumptive heterothallic ancestor, whereas most genes from the male SDR are absent. However, we found a multicopy array of the male-determining gene, MID, in a different genomic location from the SDLR. Thus, in V. africanus, an ancestrally female genotype may have acquired MID and thereby gained male traits.
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Muyle A, Bachtrog D, Marais GAB, Turner JMA. Epigenetics drive the evolution of sex chromosomes in animals and plants. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200124. [PMID: 33866802 DOI: 10.1098/rstb.2020.0124] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We review how epigenetics affect sex chromosome evolution in animals and plants. In a few species, sex is determined epigenetically through the action of Y-encoded small RNAs. Epigenetics is also responsible for changing the sex of individuals through time, even in species that carry sex chromosomes, and could favour species adaptation through breeding system plasticity. The Y chromosome accumulates repeats that become epigenetically silenced which leads to an epigenetic conflict with the expression of Y genes and could accelerate Y degeneration. Y heterochromatin can be lost through ageing, which activates transposable elements and lowers male longevity. Y chromosome degeneration has led to the evolution of meiotic sex chromosome inactivation in eutherians (placentals) and marsupials, and dosage compensation mechanisms in animals and plants. X-inactivation convergently evolved in eutherians and marsupials via two independently evolved non-coding RNAs. In Drosophila, male X upregulation by the male specific lethal (MSL) complex can spread to neo-X chromosomes through the transposition of transposable elements that carry an MSL-binding motif. We discuss similarities and possible differences between plants and animals and suggest future directions for this dynamic field of research. This article is part of the theme issue 'How does epigenetics influence the course of evolution?'
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Affiliation(s)
- Aline Muyle
- University of California Irvine, Irvine, CA 92697, USA
| | - Doris Bachtrog
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA, USA
| | - Gabriel A B Marais
- Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Évolutive UMR 5558, F-69622 Villeurbanne, France.,LEAF- Linking Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia, Universidade de Lisboa, Portugal
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30
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Glémin S. Balancing selection in self-fertilizing populations. Evolution 2021; 75:1011-1029. [PMID: 33675041 DOI: 10.1111/evo.14194] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Accepted: 01/17/2021] [Indexed: 11/30/2022]
Abstract
Self-fertilization commonly occurs in hermaphroditic species, either occasionally or as the main reproductive mode. It strongly affects the genetic functioning of a population by increasing homozygosity and genetic drift and reducing the effectiveness of recombination. Balancing selection is a form of selection that maintains polymorphism, which has been extensively studied in outcrossing species. Yet, despite recent developments, the analysis of balancing selection in partially selfing species is limited to specific cases and a general treatment is still lacking. In particular, it is unclear whether selfing globally reduced the efficacy of balancing selection as in the well-known case of overdominance. I provide a unifying framework, quantify how selfing affects the maintenance of polymorphism and the efficacy of the different form of balancing selection, and show that they can be classified into two main categories: overdominance-like selection (including true overdominance, selection variable in space and time, and antagonistic selection), which is strongly affected by selfing, and negative frequency dependent selection, which is barely affected by selfing, even at multiple loci. I also provide simple analytical results for all cases under the assumption of weak selection. This framework provides theoretical background to analyze the genomic signature of balancing selection in partially selfing species. It also sheds new light on the evolution of selfing species, including the evolution of selfing syndrome, the interaction with pathogens, and the evolutionary fate of selfing lineages.
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Affiliation(s)
- Sylvain Glémin
- CNRS, ECOBIO (Ecosystèmes, biodiversité, évolution), University of Rennes 1, UMR 6553, Rennes, France.,Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Uppsala, 752 36, Sweden
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31
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Cornetti L, Fields PD, Ebert D. Genomic characterization of selfing in the cyclic parthenogen Daphnia magna. J Evol Biol 2021; 34:792-802. [PMID: 33704857 DOI: 10.1111/jeb.13780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Revised: 02/23/2021] [Accepted: 03/06/2021] [Indexed: 11/29/2022]
Abstract
Inbreeding refers to the fusion of related individuals' gametes, with self-fertilization (selfing) being an extreme form of inbreeding-involving gametes produced by the same individual. Selfing is expected to reduce heterozygosity by an average of 50% in one generation; however, little is known about the empirical variation on a genome level surrounding this figure and the factors that affect variation. We selfed genotypes of the cyclic parthenogen Daphnia magna and analysed whole genomes of mothers and selfed offspring, observing the predicted 50% heterozygosity reduction on average. We also saw substantial variation around this value and significant differences among mother-offspring pairs. Crossover analysis confirmed the known trend of recombination occurring more often towards the telomeres. This effect was shown, through simulations, to increase the variance of heterozygosity reduction compared to when a uniform distribution of crossovers was used. Similarly, we simulated inbred line production after several generations of selfing and we observed higher variance in achieved homozygosity when we consider a higher recombination rate towards the telomeres. Our empirical and simulation study highlights that the expected mean values of heterozygosity reduction show remarkable variation, which can help understand, for example, differences among inbred individuals.
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Affiliation(s)
- Luca Cornetti
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland
| | - Peter D Fields
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland
| | - Dieter Ebert
- Department of Environmental Sciences, Zoology, University of Basel, Basel, Switzerland
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32
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Xie QP, Li BB, Zhan W, Liu F, Tan P, Wang X, Lou B. A Transient Hermaphroditic Stage in Early Male Gonadal Development in Little Yellow Croaker, Larimichthys polyactis. Front Endocrinol (Lausanne) 2021; 11:542942. [PMID: 33584533 PMCID: PMC7873647 DOI: 10.3389/fendo.2020.542942] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 12/07/2020] [Indexed: 01/13/2023] Open
Abstract
Animal taxa show remarkable variability in sexual reproduction, where separate sexes, or gonochorism, is thought to have evolved from hermaphroditism for most cases. Hermaphroditism accounts for 5% in animals, and sequential hermaphroditism has been found in teleost. In this study, we characterized a novel form of the transient hermaphroditic stage in little yellow croaker (Larimichthys polyactis) during early gonadal development. The ovary and testis were indistinguishable from 7 to 40 days post-hatching (dph). Morphological and histological examinations revealed an intersex stage of male gonads between 43 and 80 dph, which consist of germ cells, somatic cells, efferent duct, and early primary oocytes (EPOs). These EPOs in testis degenerate completely by 90 dph through apoptosis yet can be rescued by exogenous 17-β-estradiol. Male germ cells enter the mitotic flourishing stage before meiosis is initiated at 180 dph, and they undergo normal spermatogenesis to produce functional sperms. This transient hermaphroditic stage is male-specific, and the ovary development appears to be normal in females. This developmental pattern is not found in the sister species Larimichthys crocea or any other closely related species. Further examinations of serum hormone levels indicate that the absence of 11-ketotestosterone and elevated levels of 17-β-estradiol delineate the male intersex gonad stage, providing mechanistic insights on this unique phenomenon. Our research is the first report on male-specific transient hermaphroditism and will advance the current understanding of fish reproductive biology. This unique gonadal development pattern can serve as a useful model for studying the evolutionary relationship between hermaphroditism and gonochorism, as well as teleost sex determination and differentiation strategies.
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Affiliation(s)
- Qing-Ping Xie
- Institute of Hydrobiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
- Marine Fisheries Research Institute of Zhejiang Province, Zhoushan, China
| | - Bing-Bing Li
- School of Fishery, Zhejiang Ocean University, Zhoushan, China
| | - Wei Zhan
- Institute of Hydrobiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Feng Liu
- Institute of Hydrobiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
| | - Peng Tan
- Marine Fisheries Research Institute of Zhejiang Province, Zhoushan, China
| | - Xu Wang
- Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL, United States
- Alabama Agricultural Experiment Station, Auburn, AL, United States
- The HudsonAlpha Institute for Biotechnology, Huntsville, AL, United States
| | - Bao Lou
- Institute of Hydrobiology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China
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33
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De Kort H, Prunier JG, Ducatez S, Honnay O, Baguette M, Stevens VM, Blanchet S. Life history, climate and biogeography interactively affect worldwide genetic diversity of plant and animal populations. Nat Commun 2021; 12:516. [PMID: 33483517 PMCID: PMC7822833 DOI: 10.1038/s41467-021-20958-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Accepted: 01/04/2021] [Indexed: 01/30/2023] Open
Abstract
Understanding how biological and environmental factors interactively shape the global distribution of plant and animal genetic diversity is fundamental to biodiversity conservation. Genetic diversity measured in local populations (GDP) is correspondingly assumed representative for population fitness and eco-evolutionary dynamics. For 8356 populations across the globe, we report that plants systematically display much lower GDP than animals, and that life history traits shape GDP patterns both directly (animal longevity and size), and indirectly by mediating core-periphery patterns (animal fecundity and plant dispersal). Particularly in some plant groups, peripheral populations can sustain similar GDP as core populations, emphasizing their potential conservation value. We further find surprisingly weak support for general latitudinal GDP trends. Finally, contemporary rather than past climate contributes to the spatial distribution of GDP, suggesting that contemporary environmental changes affect global patterns of GDP. Our findings generate new perspectives for the conservation of genetic resources at worldwide and taxonomic-wide scales.
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Affiliation(s)
- H De Kort
- Plant Conservation and Population Biology, Department of Biology, University of Leuven, Heverlee, Belgium.
| | - J G Prunier
- Centre National de la Recherche Scientifique, SETE Station d'Ecologie Théorique et Expérimentale, UMR 5321, Moulis, France
| | - S Ducatez
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - O Honnay
- Plant Conservation and Population Biology, Department of Biology, University of Leuven, Heverlee, Belgium
| | - M Baguette
- Centre National de la Recherche Scientifique, SETE Station d'Ecologie Théorique et Expérimentale, UMR 5321, Moulis, France
- Institut Systématique, Evolution, Biodiversité (ISYEB), UMR 7205 Museum National d'Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, Paris, France
| | - V M Stevens
- Centre National de la Recherche Scientifique, SETE Station d'Ecologie Théorique et Expérimentale, UMR 5321, Moulis, France
| | - S Blanchet
- Centre National de la Recherche Scientifique, SETE Station d'Ecologie Théorique et Expérimentale, UMR 5321, Moulis, France
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34
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Ramzan F, Kim HT, Younis A, Ramzan Y, Lim KB. Genetic assessment of the effects of self-fertilization in a Lilium L. hybrids using molecular cytogenetic methods (FISH and ISSR). Saudi J Biol Sci 2020; 28:1770-1778. [PMID: 33732061 PMCID: PMC7938132 DOI: 10.1016/j.sjbs.2020.12.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Revised: 12/06/2020] [Accepted: 12/09/2020] [Indexed: 11/28/2022] Open
Abstract
Self-fertilization (also termed selfing) is a mode of reproduction that occurs in hermaphrodites and has evolved several times in various plant and animal species. A transition from outbreeding to selfing in hermaphroditic flowers is typically associated with changes in flower morphology and functionality. This study aimed to identify genetic effects of selfing in the F2 progeny of F1 hybrid developed by crossing Lilium lancifolium with the Asiatic Lilium hybrid ‘Dreamland.’ Fluorescence in situ hybridization (FISH) and inter-simple sequence repeats (ISSR) techniques were used to detect genetic variations in plants produced by selfing. The FISH results showed that F1 hybrid were similar to the female parent (L. lancifolium) regarding the 45S loci, but F2 individuals showed variation in the number and location of the respective loci. In F2 progeny, F2-2, F2-3, F2-4, F2-5, and F2-8 hybrids expressed two strong and one weak 5S signal on chromosome 3, whereas F2-7 and F2-9 individuals expressed one strong and two weak signals. Only two strong 5S signals were detected in an F2-1 plant. The ISSR results showed a maximum similarity value of 0.6269 between the female parent and the F2-2 hybrid. Regarding similarity to the male parent, a maximum value of 0.6119 was found in the F2-1 and F2-2 hybrids. The highest genetic distance from L. lancifolium and the Asiatic Lilium hybrid ‘Dreamland’ was observed in the F2-4 progeny (0.6352 and 0.7547, respectively). Phylogenetic relationships showed that the F2 progeny were closer to the male parent than to the female parent. Self-fertilization showed effects on variation among the F2 progeny, and effects on the genome were confirmed using FISH and ISSR analyses.
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Affiliation(s)
- Fahad Ramzan
- Deptartment of Horticulture, Kyungpook National University, Daegu 41566, South Korea
| | - Hyoung Tae Kim
- Deptartment of Horticulture, Kyungpook National University, Daegu 41566, South Korea
| | - Adnan Younis
- Institute of Horticultural Sciences, University of Agriculture, Faisalabad 38040, Pakistan
| | - Yasir Ramzan
- Wheat Research Institute, AARI, Faisalabad, Pakistan
| | - Ki-Byung Lim
- Deptartment of Horticulture, Kyungpook National University, Daegu 41566, South Korea
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35
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More than meets the eye: syntopic and morphologically similar mangrove killifish species show different mating systems and patterns of genetic structure along the Brazilian coast. Heredity (Edinb) 2020; 125:340-352. [PMID: 32826964 DOI: 10.1038/s41437-020-00356-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 08/06/2020] [Accepted: 08/08/2020] [Indexed: 01/22/2023] Open
Abstract
Different mating systems can strongly affect the extent of genetic diversity and population structure among species. Given the increased effects of genetic drift on reduced population size, theory predicts that species undergoing self-fertilisation should have greater population structure than outcrossed species; however, demographic dynamics may affect this scenario. The mangrove killifish clade is composed of the two only known examples of self-fertilising species among vertebrates (Kryptolebias marmoratus and Kryptolebias hermaphroditus). A third species in this clade, Kryptolebias ocellatus, inhabits mangrove forests in southeast Brazil; however, its mating system and patterns of genetic structure have been rarely explored. Here, we examined the genetic structure and phylogeographic patterns of K. ocellatus along its distribution, using mitochondrial DNA and microsatellites to compare its patterns of genetic structure with the predominantly selfing and often-syntopic, K. hermaphroditus. Our results indicate that K. ocellatus reproduces mainly by outcrossing, with no current evidence of selfing, despite being an androdioecious species. Our results also reveal a stronger population subdivision in K. ocellatus compared to K. hermaphroditus, contrary to the theoretical predictions based on reproductive biology of the two species. Our findings indicate that, although morphologically similar, K. ocellatus and K. hermaphroditus had remarkably different evolutionary histories when colonising the same mangrove areas in southeastern Brazil, with other factors (e.g., time of colonisation, dispersal/establishment capacity) having more profound effects on the current population structuring of those species than differences in mating systems.
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36
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Hörandl E, Hadacek F. Oxygen, life forms, and the evolution of sexes in multicellular eukaryotes. Heredity (Edinb) 2020; 125:1-14. [PMID: 32415185 PMCID: PMC7413252 DOI: 10.1038/s41437-020-0317-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 04/26/2020] [Accepted: 04/26/2020] [Indexed: 12/27/2022] Open
Abstract
The evolutionary advantage of different sexual systems in multicellular eukaryotes is still not well understood, because the differentiation into male and female individuals halves offspring production compared with asexuality. Here we propose that various physiological adaptations to oxidative stress could have forged sessility versus motility, and consequently the evolution of sexual systems in multicellular animals, plants, and fungi. Photosynthesis causes substantial amounts of oxidative stress in photoautotrophic plants and, likewise, oxidative chemistry of polymer breakdown, cellulose and lignin, for saprotrophic fungi. In both cases, its extent precludes motility, an additional source of oxidative stress. Sessile life form and the lack of neuronal systems, however, limit options for mate recognition and adult sexual selection, resulting in inefficient mate-searching systems. Hence, sessility requires that all individuals can produce offspring, which is achieved by hermaphroditism in plants and/or by multiple mating types in fungi. In animals, motility requires neuronal systems, and muscle activity, both of which are highly sensitive to oxidative damage. As a consequence, motility has evolved in animals as heterotrophic organisms that (1) are not photosynthetically active, and (2) are not primary decomposers. Adaptations to motility provide prerequisites for an active mating behavior and efficient mate-searching systems. These benefits compensate for the "cost of males", and may explain the early evolution of sex chromosomes in metazoans. We conclude that different sexual systems evolved under the indirect physiological constraints of lifestyles.
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Affiliation(s)
- Elvira Hörandl
- Department of Systematics, Biodiversity and Evolution of Plants, University of Goettingen, Göttingen, Germany.
| | - Franz Hadacek
- Department of Plant Biochemistry, University of Goettingen, Göttingen, Germany
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37
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Felmy A, Weissert N, Travis J, Jokela J. Mate availability determines use of alternative reproductive phenotypes in hermaphrodites. Behav Ecol 2020. [DOI: 10.1093/beheco/araa046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
In many species, individuals can employ alternative reproductive phenotypes, with profound consequences for individual fitness and population dynamics. This is particularly relevant for self-compatible hermaphrodites, which have exceptionally many reproductive options. Here we investigated the occurrence of reproductive phenotypes in the simultaneously hermaphroditic freshwater snail Radix balthica under experimentally simulated conditions of low versus moderate population density. We captured all mating behavior on camera and measured individual female lifetime reproductive success. We found every possible reproductive phenotype: (1) both male and female (i.e., truly hermaphroditic) reproduction, (2) purely female and (3) purely male reproduction, (4) male reproduction combined with self-fertilization and (5) female mating activity, (6) pure self-fertilization without mating and (7–8) two types of reproductive failure. Variation in alternative reproductive phenotypes was explained by mate availability (10.8%) and individual condition, approximated by a snail’s mean daily growth rate (17.5%). Increased mate availability resulted in a lower diversity of reproductive phenotypes, in particular increasing the frequency of true hermaphrodites. However, it lowered phenotype-specific fecundities and hence reduced the population growth rate. Snails in better condition were more likely to reproduce as true hermaphrodites or pure females, whereas low-condition snails tended to suffer reproductive failure. Overall, we show substantial variation in alternative reproductive phenotypes in a hermaphrodite, which is possibly in part maintained by fluctuations in population density and thus mate availability, and by variation in individual condition. We also provide evidence of an almost 2-fold increase in clutch size that can be ascribed specifically to mating as a female.
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Affiliation(s)
- Anja Felmy
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, Dübendorf, Switzerland
- ETH Zurich, D-USYS, Institute of Integrative Biology, Universitätstrasse 16, Zurich, Switzerland
- Department of Zoology, University of Oxford, Oxford, UK
| | - Nora Weissert
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, Dübendorf, Switzerland
| | - Joseph Travis
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Jukka Jokela
- Department of Aquatic Ecology, EAWAG, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, Dübendorf, Switzerland
- ETH Zurich, D-USYS, Institute of Integrative Biology, Universitätstrasse 16, Zurich, Switzerland
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38
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Nozaki H, Mahakham W, Heman W, Matsuzaki R, Kawachi M. A new preferentially outcrossing monoicous species of Volvox sect. Volvox (Chlorophyta) from Thailand. PLoS One 2020; 15:e0235622. [PMID: 32614898 PMCID: PMC7332039 DOI: 10.1371/journal.pone.0235622] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 06/18/2020] [Indexed: 11/25/2022] Open
Abstract
Volvox sect. Volvox is an interesting group of green algae; it comprises mostly monoicous species, but evidence suggests an evolution towards dioicy. Based on cultured strains originating from Thailand, we describe Volvox longispiniferus, a novel species in Volvox sect. Volvox. This species is distinguished from others in the section by the large number of sperm packets in its monoicous sexual spheroids and by the long spines on its zygote wall. Phylogenetic analyses indicate that V. longispiniferus is distinct from the other species of two monophyletic groups within Volvox sect. Volvox. In addition, the novel species produces more zygotes when different cultures are combined compared with a single culture, suggesting a preference for outcrossing.
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Affiliation(s)
- Hisayoshi Nozaki
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
- * E-mail:
| | - Wuttipong Mahakham
- Department of Biology, Faculty of Science, Khon Kaen University, Khon Kaen, Thailand
| | - Wirawan Heman
- Department of Science and Mathematics, Faculty of Science and Health Technology, Kalasin University, Thailand
| | - Ryo Matsuzaki
- Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Masanobu Kawachi
- Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan
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39
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Spoelhof JP, Keeffe R, McDaniel SF. Does reproductive assurance explain the incidence of polyploidy in plants and animals? THE NEW PHYTOLOGIST 2020; 227:14-21. [PMID: 31883115 DOI: 10.1111/nph.16396] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Accepted: 12/17/2019] [Indexed: 06/10/2023]
Affiliation(s)
- Jonathan P Spoelhof
- Florida Museum of Natural History, University of Florida, Gainesville, FL, 32611, USA
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Rachel Keeffe
- Florida Museum of Natural History, University of Florida, Gainesville, FL, 32611, USA
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
| | - Stuart F McDaniel
- Department of Biology, University of Florida, Gainesville, FL, 32611, USA
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40
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Abu Awad D, Roze D. Epistasis, inbreeding depression, and the evolution of self-fertilization. Evolution 2020; 74:1301-1320. [PMID: 32386235 DOI: 10.1111/evo.13961] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 02/21/2020] [Indexed: 11/29/2022]
Abstract
Inbreeding depression resulting from partially recessive deleterious alleles is thought to be the main genetic factor preventing self-fertilizing mutants from spreading in outcrossing hermaphroditic populations. However, deleterious alleles may also generate an advantage to selfers in terms of more efficient purging, while the effects of epistasis among those alleles on inbreeding depression and mating system evolution remain little explored. In this article, we use a general model of selection to disentangle the effects of different forms of epistasis (additive-by-additive, additive-by-dominance, and dominance-by-dominance) on inbreeding depression and on the strength of selection for selfing. Models with fixed epistasis across loci, and models of stabilizing selection acting on quantitative traits (generating distributions of epistasis) are considered as special cases. Besides its effects on inbreeding depression, epistasis may increase the purging advantage associated with selfing (when it is negative on average), while the variance in epistasis favors selfing through the generation of linkage disequilibria that increase mean fitness. Approximations for the strengths of these effects are derived, and compared with individual-based simulation results.
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Affiliation(s)
- Diala Abu Awad
- Department of Population Genetics, Technical University of Munich, Munich, 80333, Germany
| | - Denis Roze
- Evolutionary Biology and Ecology of Algae, UMI 3614, CNRS, Roscoff, 29688, France.,Station Biologique de Roscoff, Sorbonne Université, Roscoff, 29688, France
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41
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Olsen KC, Ryan WH, Winn AA, Kosman ET, Moscoso JA, Krueger-Hadfield SA, Burgess SC, Carlon DB, Grosberg RK, Kalisz S, Levitan DR. Inbreeding shapes the evolution of marine invertebrates. Evolution 2020; 74:871-882. [PMID: 32191349 PMCID: PMC7383701 DOI: 10.1111/evo.13951] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 02/06/2020] [Accepted: 02/21/2020] [Indexed: 12/22/2022]
Abstract
Inbreeding is a potent evolutionary force shaping the distribution of genetic variation within and among populations of plants and animals. Yet, our understanding of the forces shaping the expression and evolution of nonrandom mating in general, and inbreeding in particular, remains remarkably incomplete. Most research on plant mating systems focuses on self-fertilization and its consequences for automatic selection, inbreeding depression, purging, and reproductive assurance, whereas studies of animal mating systems have often assumed that inbreeding is rare, and that natural selection favors traits that promote outbreeding. Given that many sessile and sedentary marine invertebrates and marine macroalgae share key life history features with seed plants (e.g., low mobility, modular construction, and the release of gametes into the environment), their mating systems may be similar. Here, we show that published estimates of inbreeding coefficients (FIS ) for sessile and sedentary marine organisms are similar and at least as high as noted in terrestrial seed plants. We also found that variation in FIS within invertebrates is related to the potential to self-fertilize, disperse, and choose mates. The similarity of FIS for these organismal groups suggests that inbreeding could play a larger role in the evolution of sessile and sedentary marine organisms than is currently recognized. Specifically, associations between traits of marine invertebrates and FIS suggest that inbreeding could drive evolutionary transitions between hermaphroditism and separate sexes, direct development and multiphasic life cycles, and external and internal fertilization.
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Affiliation(s)
- Kevin C Olsen
- Department of Biological Science, Florida State University, Tallahassee, Florida, 32304
| | - Will H Ryan
- Department of Biology, University of Alabama at Birmingham, Birmingham, Alabama, 35294
| | - Alice A Winn
- Department of Biological Science, Florida State University, Tallahassee, Florida, 32304
| | - Ellen T Kosman
- Department of Biological Science, Florida State University, Tallahassee, Florida, 32304
| | - Jose A Moscoso
- Department of Ecology and Evolution, Stony Brook University, Stony Brook, New York, 11794
| | | | - Scott C Burgess
- Department of Biological Science, Florida State University, Tallahassee, Florida, 32304
| | - David B Carlon
- The Biology Department, Bowdoin College, Brunswick, Maine, 04011.,Schiller Coastal Studies Center, Bowdoin College, Orr's Island, Maine, 04066
| | - Richard K Grosberg
- Coastal and Marine Sciences Institute, University of California Davis, Davis, California, 95616
| | - Susan Kalisz
- Department of Ecology and Evolutionary Biology, University of Tennessee Knoxville, Knoxville, Tennessee, 37996
| | - Don R Levitan
- Department of Biological Science, Florida State University, Tallahassee, Florida, 32304
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42
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Sellinger TPP, Abu Awad D, Moest M, Tellier A. Inference of past demography, dormancy and self-fertilization rates from whole genome sequence data. PLoS Genet 2020; 16:e1008698. [PMID: 32251472 PMCID: PMC7173940 DOI: 10.1371/journal.pgen.1008698] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 04/21/2020] [Accepted: 02/24/2020] [Indexed: 02/04/2023] Open
Abstract
Several methods based on the Sequential Markovian coalescence (SMC) have been developed that make use of genome sequence data to uncover population demographic history, which is of interest in its own right and is a key requirement to generate a null model for selection tests. While these methods can be applied to all possible kind of species, the underlying assumptions are sexual reproduction in each generation and non-overlapping generations. However, in many plants, invertebrates, fungi and other taxa, those assumptions are often violated due to different ecological and life history traits, such as self-fertilization or long term dormant structures (seed or egg-banking). We develop a novel SMC-based method to infer 1) the rates/parameters of dormancy and of self-fertilization, and 2) the populations' past demographic history. Using simulated data sets, we demonstrate the accuracy of our method for a wide range of demographic scenarios and for sequence lengths from one to 30 Mb using four sampled genomes. Finally, we apply our method to a Swedish and a German population of Arabidopsis thaliana demonstrating a selfing rate of ca. 0.87 and the absence of any detectable seed-bank. In contrast, we show that the water flea Daphnia pulex exhibits a long lived egg-bank of three to 18 generations. In conclusion, we here present a novel method to infer accurate demographies and life-history traits for species with selfing and/or seed/egg-banks. Finally, we provide recommendations for the use of SMC-based methods for non-model organisms, highlighting the importance of the per site and the effective ratios of recombination over mutation.
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Affiliation(s)
| | - Diala Abu Awad
- Department of Population Genetics, Technische Universitaet Muenchen, Freising, Germany
| | - Markus Moest
- Department of Ecology, University of Innsbruck, Innsbruck, Austria
| | - Aurélien Tellier
- Department of Population Genetics, Technische Universitaet Muenchen, Freising, Germany
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43
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Kaufmann P, Schärer L. Is the initiation of selfing linked to a hermaphrodite's female or male reproductive function? Behav Ecol Sociobiol 2020; 74:41. [PMID: 32214615 PMCID: PMC7080307 DOI: 10.1007/s00265-020-2816-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 02/11/2020] [Accepted: 02/24/2020] [Indexed: 11/30/2022]
Abstract
ABSTRACT There is an ongoing debate about whether simultaneous hermaphrodites capable of selfing should prefer selfing over outcrossing or vice versa. While many theoretical models predict a transmission advantage for alleles that favour selfing, empirical studies often reveal low selfing rates. Despite these considerations, the underlying mechanisms that determine reproductive strategies in simultaneously hermaphroditic animals are poorly understood. In our study on the facultatively selfing free-living flatworm, Macrostomum hystrix, we ask whether the initiation of selfing, as inferred from the differential spatial distribution of received sperm, is linked to an individual's female or male reproductive function. Specifically, the initiation of selfing could (i) be linked to the male function, when an individual is unable to donate sperm to others and hence donates sperm to self, or it could (ii) be linked to the female function, when an individual fails to receive sperm from others-and hence is unable to fertilize its eggs via outcrossing-thus inducing it to self-fertilize. We experimentally created a social environment that allowed focals to outcross via sperm donation, but simultaneously prevented them from receiving sperm-by pairing them with a partner lacking the male copulatory organ-so that fertilization of the focal's eggs was restricted to selfing. Our results suggest that such focals generally do not initiate selfing, while we readily observe selfing in isolated worms. This suggests that in isolated M. hystrix, it is the male function that is linked to the initiation of selfing, likely due to a lack of opportunities for sperm donation. SIGNIFICANCE STATEMENT A variety of simultaneously hermaphroditic animals are capable of reproducing via both selfing and outcrossing. While the reproductive choices of such animals can be modelled by the joint action of genetic (e.g. inbreeding depression) and ecological factors (e.g. partner availability), experimental evaluation of theoretical results is often lacking. By manipulating the social environment of focal individuals, we here provide evidence that explores the respective role that the co-occurring male and female sex functions have on the initiation of selfing in a simultaneously hermaphroditic flatworm species. Specifically, our results suggest that the initiation of selfing is linked to the worm's male function. Insights about which function is linked to the initiation of selfing may ultimately help to better understand reproductive decisions in simultaneous hermaphrodites.
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Affiliation(s)
- Philipp Kaufmann
- Department of Environmental Sciences, Zoological Institute, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland
- Present Address: Department of Evolutionary Biology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36 Uppsala, Sweden
| | - Lukas Schärer
- Department of Environmental Sciences, Zoological Institute, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland
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44
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Hartfield M, Bataillon T. Selective Sweeps Under Dominance and Inbreeding. G3 (BETHESDA, MD.) 2020; 10:1063-1075. [PMID: 31974096 PMCID: PMC7056974 DOI: 10.1534/g3.119.400919] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 01/18/2020] [Indexed: 12/26/2022]
Abstract
A major research goal in evolutionary genetics is to uncover loci experiencing positive selection. One approach involves finding 'selective sweeps' patterns, which can either be 'hard sweeps' formed by de novo mutation, or 'soft sweeps' arising from recurrent mutation or existing standing variation. Existing theory generally assumes outcrossing populations, and it is unclear how dominance affects soft sweeps. We consider how arbitrary dominance and inbreeding via self-fertilization affect hard and soft sweep signatures. With increased self-fertilization, they are maintained over longer map distances due to reduced effective recombination and faster beneficial allele fixation times. Dominance can affect sweep patterns in outcrossers if the derived variant originates from either a single novel allele, or from recurrent mutation. These models highlight the challenges in distinguishing hard and soft sweeps, and propose methods to differentiate between scenarios.
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Affiliation(s)
- Matthew Hartfield
- Department of Ecology and Evolutionary Biology, University of Toronto, Ontario M5S 3B2, Canada,
- Bioinformatics Research Centre, Aarhus University, Aarhus 8000, Denmark, and
- Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh EH9 3FL, United Kingdom
| | - Thomas Bataillon
- Bioinformatics Research Centre, Aarhus University, Aarhus 8000, Denmark, and
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45
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Giannakara A, Ramm SA. Evidence for inter-population variation in waiting times in a self-fertilizing flatworm. INVERTEBR REPROD DEV 2020. [DOI: 10.1080/07924259.2020.1732485] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
| | - Steven A. Ramm
- Evolutionary Biology, Bielefeld University, Bielefeld, Germany
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46
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Abstract
Egg trading-whereby simultaneous hermaphrodites exchange each other's eggs for fertilization-constitutes one of the few rigorously documented and most widely cited examples of direct reciprocity among unrelated individuals. Yet how egg trading may initially invade a population of nontrading simultaneous hermaphrodites is still unresolved. Here, we address this question with an analytical model that considers mate encounter rates and costs of egg production in a population that may include traders (who provide eggs for fertilization only if their partners also have eggs to reciprocate), providers (who provide eggs regardless of whether their partners have eggs to reciprocate), and withholders (cheaters who mate only in the male role and just use their eggs to elicit egg release from traders). Our results indicate that a combination of intermediate mate encounter rates, sufficiently high costs of egg production, and a sufficiently high probability that traders detect withholders (in which case eggs are not provided) is conducive to the evolution of egg trading. Under these conditions, traders can invade-and resist invasion from-providers and withholders alike. The prediction that egg trading evolves only under these specific conditions is consistent with the rare occurrence of this mating system among simultaneous hermaphrodites.
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47
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Guerra V, Haynes G, Byrne M, Yasuda N, Adachi S, Nakamura M, Nakachi S, Hart MW. Nonspecific expression of fertilization genes in the crown-of-thorns Acanthaster cf. solaris: Unexpected evidence of hermaphroditism in a coral reef predator. Mol Ecol 2019; 29:363-379. [PMID: 31837059 DOI: 10.1111/mec.15332] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 11/28/2019] [Accepted: 12/10/2019] [Indexed: 01/04/2023]
Abstract
The characterization of gene expression in gametes has advanced our understanding of the molecular basis for ecological variation in reproductive success and the evolution of reproductive isolation. These advances are especially significant for ecologically important keystone predators such as the coral-eating crown-of-thorns sea stars (COTS, Acanthaster) which are the most influential predator species in Indo-Pacific coral reef ecosystems and the focus of intensive management efforts. We used RNA-seq and transcriptome assemblies to characterize the expression of genes in mature COTS gonads. We described the sequence and domain organization of eight genes with sex-specific expression and well known functions in fertilization in other echinoderms. We found unexpected expression of genes in one ovary transcriptome that are characteristic of males and sperm, including genes that encode the sperm-specific guanylate cyclase receptor for an egg pheromone, and the sperm acrosomal protein bindin. In a reassembly of previously published RNA-seq data from COTS testes, we found a complementary pattern: strong expression of four genes that are otherwise well known to encode egg-specific fertilization proteins, including the egg receptor for bindin (EBR1) and the acrosome reaction-inducing substance in the egg coat (ARIS1, ARIS2, ARIS3). We also found histological evidence of both eggs and sperm developing in the same gonad in several COTS individuals from a parallel study. These results suggest the occurrence of hermaphrodites, and the potential for reproductive assurance via self-fertilization. Our findings have implications for management of COTS populations, especially in consideration of the large size and massive fecundity of these sea stars.
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Affiliation(s)
- Vanessa Guerra
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada.,Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - Gwilym Haynes
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada.,Department of Biology, Langara College, Vancouver, British Columbia, Canada
| | - Maria Byrne
- Schools of Medical and Biological Sciences, The University of Sydney, Sydney, Australia
| | - Nina Yasuda
- Department of Marine Biology and Environmental Science, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan
| | - Souta Adachi
- School of Marine Science and Technology, Tokai University, Shimizu, Shizuoka, Japan
| | - Masako Nakamura
- School of Marine Science and Technology, Tokai University, Shimizu, Shizuoka, Japan
| | | | - Michael W Hart
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada
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48
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Tannenbaum C, Ellis RP, Eyssel F, Zou J, Schiebinger L. Sex and gender analysis improves science and engineering. Nature 2019; 575:137-146. [DOI: 10.1038/s41586-019-1657-6] [Citation(s) in RCA: 202] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 08/27/2019] [Indexed: 01/17/2023]
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49
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Cutter AD. Reproductive transitions in plants and animals: selfing syndrome, sexual selection and speciation. THE NEW PHYTOLOGIST 2019; 224:1080-1094. [PMID: 31336389 DOI: 10.1111/nph.16075] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/17/2019] [Indexed: 05/23/2023]
Abstract
The evolution of predominant self-fertilisation frequently coincides with the evolution of a collection of phenotypes that comprise the 'selfing syndrome', in both plants and animals. Genomic features also display a selfing syndrome. Selfing syndrome traits often involve changes to male and female reproductive characters that were subject to sexual selection and sexual conflict in the obligatorily outcrossing ancestor, including the gametic phase for both plants and animals. Rapid evolution of reproductive traits, due to both relaxed selection and directional selection under the new status of predominant selfing, lays the genetic groundwork for reproductive isolation. Consequently, shifts in sexual selection pressures coupled to transitions to selfing provide a powerful paradigm for investigating the speciation process. Plant and animal studies, however, emphasise distinct selective forces influencing reproductive-mode transitions: genetic transmission advantage to selfing or reproductive assurance outweighing the costs of inbreeding depression vs the costs of males and meiosis. Here, I synthesise links between sexual selection, evolution of selfing and speciation, with particular focus on identifying commonalities and differences between plant and animal systems and pointing to areas warranting further synergy.
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Affiliation(s)
- Asher D Cutter
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON, M5S 3B2, Canada
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50
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Ho EKH, Bartkowska M, Wright SI, Agrawal AF. Population genomics of the facultatively asexual duckweed Spirodela polyrhiza. THE NEW PHYTOLOGIST 2019; 224:1361-1371. [PMID: 31298732 DOI: 10.1111/nph.16056] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 06/18/2019] [Indexed: 06/10/2023]
Abstract
Clonal propagation allows some plant species to achieve massive population sizes quickly but also reduces the evolutionary independence of different sites in the genome. We examine genome-wide genetic diversity in Spirodela polyrhiza, a duckweed that reproduces primarily asexually. We find that this geographically widespread and numerically abundant species has very low levels of genetic diversity. Diversity at nonsynonymous sites relative to synonymous sites is high, suggesting that purifying selection is weak. A potential explanation for this observation is that a very low frequency of sex renders selection ineffective. However, there is a pronounced decay in linkage disequilibrium over 40 kb, suggesting that though sex may be rare at the individual level it is not too infrequent at the population level. In addition, neutral diversity is affected by the physical proximity of selected sites, which would be unexpected if sex was exceedingly rare at the population level. The amount of genetic mixing as assessed by the decay in linkage disequilibrium is not dissimilar from selfing species such as Arabidopsis thaliana, yet selection appears to be much less effective in duckweed. We discuss alternative explanations for the signature of weak purifying selection.
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Affiliation(s)
- Eddie K H Ho
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
| | - Magdalena Bartkowska
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
| | - Stephen I Wright
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
- Center for Analysis of Genome Evolution and Function, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
| | - Aneil F Agrawal
- Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
- Center for Analysis of Genome Evolution and Function, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
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