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Di C, Lohmueller KE. Revisiting Dominance in Population Genetics. Genome Biol Evol 2024; 16:evae147. [PMID: 39114967 PMCID: PMC11306932 DOI: 10.1093/gbe/evae147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/24/2024] [Indexed: 08/11/2024] Open
Abstract
Dominance refers to the effect of a heterozygous genotype relative to that of the two homozygous genotypes. The degree of dominance of mutations for fitness can have a profound impact on how deleterious and beneficial mutations change in frequency over time as well as on the patterns of linked neutral genetic variation surrounding such selected alleles. Since dominance is such a fundamental concept, it has received immense attention throughout the history of population genetics. Early work from Fisher, Wright, and Haldane focused on understanding the conceptual basis for why dominance exists. More recent work has attempted to test these theories and conceptual models by estimating dominance effects of mutations. However, estimating dominance coefficients has been notoriously challenging and has only been done in a few species in a limited number of studies. In this review, we first describe some of the early theoretical and conceptual models for understanding the mechanisms for the existence of dominance. Second, we discuss several approaches used to estimate dominance coefficients and summarize estimates of dominance coefficients. We note trends that have been observed across species, types of mutations, and functional categories of genes. By comparing estimates of dominance coefficients for different types of genes, we test several hypotheses for the existence of dominance. Lastly, we discuss how dominance influences the dynamics of beneficial and deleterious mutations in populations and how the degree of dominance of deleterious mutations influences the impact of inbreeding on fitness.
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Affiliation(s)
- Chenlu Di
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
| | - Kirk E Lohmueller
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
- Interdepartmental Program in Bioinformatics, University of California, Los Angeles, CA, USA
- Department of Human Genetics, David Geffen School of Medicine, Los Angeles, CA, USA
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2
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Angst P, Haag CR, Ben-Ami F, Fields PD, Ebert D. Genome-Wide Allele Frequency Changes Reveal That Dynamic Metapopulations Evolve Differently. Mol Biol Evol 2024; 41:msae128. [PMID: 38935572 PMCID: PMC11229820 DOI: 10.1093/molbev/msae128] [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: 02/14/2024] [Revised: 06/14/2024] [Accepted: 06/20/2024] [Indexed: 06/29/2024] Open
Abstract
Two important characteristics of metapopulations are extinction-(re)colonization dynamics and gene flow between subpopulations. These processes can cause strong shifts in genome-wide allele frequencies that are generally not observed in "classical" (large, stable, and panmictic) populations. Subpopulations founded by one or a few individuals, the so-called propagule model, are initially expected to show intermediate allele frequencies at polymorphic sites until natural selection and genetic drift drive allele frequencies toward a mutation-selection-drift equilibrium characterized by a negative exponential-like distribution of the site frequency spectrum. We followed changes in site frequency spectrum distribution in a natural metapopulation of the cyclically parthenogenetic pond-dwelling microcrustacean Daphnia magna using biannual pool-seq samples collected over a 5-yr period from 118 ponds occupied by subpopulations of known age. As expected under the propagule model, site frequency spectra in newly founded subpopulations trended toward intermediate allele frequencies and shifted toward right-skewed distributions as the populations aged. Immigration and subsequent hybrid vigor altered this dynamic. We show that the analysis of site frequency spectrum dynamics is a powerful approach to understand evolution in metapopulations. It allowed us to disentangle evolutionary processes occurring in a natural metapopulation, where many subpopulations evolve in parallel. Thereby, stochastic processes like founder and immigration events lead to a pattern of subpopulation divergence, while genetic drift leads to converging site frequency spectrum distributions in the persisting subpopulations. The observed processes are well explained by the propagule model and highlight that metapopulations evolve differently from classical populations.
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Affiliation(s)
- Pascal Angst
- Department of Environmental Sciences, Zoology, University of Basel, Basel 4051, Switzerland
| | - Christoph R Haag
- CEFE, Université de Montpellier, CNRS, EPHE, IRD, Montpellier 34293, France
- Tvärminne Zoological Station, University of Helsinki, Hanko 10900, Finland
| | - Frida Ben-Ami
- Tvärminne Zoological Station, University of Helsinki, Hanko 10900, Finland
- School of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Peter D Fields
- Department of Environmental Sciences, Zoology, University of Basel, Basel 4051, Switzerland
- Tvärminne Zoological Station, University of Helsinki, Hanko 10900, Finland
| | - Dieter Ebert
- Department of Environmental Sciences, Zoology, University of Basel, Basel 4051, Switzerland
- Tvärminne Zoological Station, University of Helsinki, Hanko 10900, Finland
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3
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Summers J, Cosgrove EJ, Bowman R, Fitzpatrick JW, Chen N. Impacts of increasing isolation and environmental variation on Florida Scrub-Jay demography. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.10.575127. [PMID: 38260596 PMCID: PMC10802623 DOI: 10.1101/2024.01.10.575127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Isolation caused by anthropogenic habitat fragmentation can destabilize populations. Populations relying on the inflow of immigrants can face reduced fitness due to inbreeding depression as fewer new individuals arrive. Empirical studies of the demographic consequences of isolation are critical to understand how populations persist through changing conditions. We used a 34-year demographic and environmental dataset from a population of cooperatively-breeding Florida Scrub-Jays ( Aphelocoma coerulescens ) to create mechanistic models linking environmental and demographic factors to population growth rates. We found that the population has not declined despite both declining immigration and increasing inbreeding, owing to a coinciding response in breeder survival. We find evidence of density-dependent immigration, breeder survival, and fecundity, indicating that interactions between vital rates and local density play a role in buffering the population against change. Our study elucidates the impacts of isolation on demography and how long-term stability is maintained via demographic responses.
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Kyriazis CC, Serieys LE, Bishop JM, Drouilly M, Viljoen S, Wayne RK, Lohmueller KE. The influence of gene flow on population viability in an isolated urban caracal population. Mol Ecol 2024; 33:e17346. [PMID: 38581173 PMCID: PMC11035096 DOI: 10.1111/mec.17346] [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: 07/20/2023] [Revised: 01/23/2024] [Accepted: 03/26/2024] [Indexed: 04/08/2024]
Abstract
Wildlife populations are becoming increasingly fragmented by anthropogenic development. Small and isolated populations often face an elevated risk of extinction, in part due to inbreeding depression. Here, we examine the genomic consequences of urbanization in a caracal (Caracal caracal) population that has become isolated in the Cape Peninsula region of the City of Cape Town, South Africa, and is thought to number ~50 individuals. We document low levels of migration into the population over the past ~75 years, with an estimated rate of 1.3 effective migrants per generation. As a consequence of this isolation and small population size, levels of inbreeding are elevated in the contemporary Cape Peninsula population (mean FROH = 0.20). Inbreeding primarily manifests as long runs of homozygosity >10 Mb, consistent with the effects of isolation due to the rapid recent growth of Cape Town. To explore how reduced migration and elevated inbreeding may impact future population dynamics, we parameterized an eco-evolutionary simulation model. We find that if migration rates do not change in the future, the population is expected to decline, though with a low projected risk of extinction. However, if migration rates decline or anthropogenic mortality rates increase, the potential risk of extinction is greatly elevated. To avert a population decline, we suggest that translocating migrants into the Cape Peninsula to initiate a genetic rescue may be warranted in the near future. Our analysis highlights the utility of genomic datasets coupled with computational simulation models for investigating the influence of gene flow on population viability.
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Affiliation(s)
- Christopher C. Kyriazis
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA
| | - Laurel E.K. Serieys
- Panthera, 8 W 40th St, 18th Floor, New York, NY 10018, USA
- Institute for Communities and Wildlife in Africa, Department of Biological Sciences, University of Cape Town, Rondebosch, 7701, South Africa
| | - Jacqueline M. Bishop
- Institute for Communities and Wildlife in Africa, Department of Biological Sciences, University of Cape Town, Rondebosch, 7701, South Africa
| | - Marine Drouilly
- Panthera, 8 W 40th St, 18th Floor, New York, NY 10018, USA
- Institute for Communities and Wildlife in Africa, Department of Biological Sciences, University of Cape Town, Rondebosch, 7701, South Africa
- Centre for Social Science Research, University of Cape Town, Rondebosch, 7701, South Africa
| | - Storme Viljoen
- Institute for Communities and Wildlife in Africa, Department of Biological Sciences, University of Cape Town, Rondebosch, 7701, South Africa
| | - Robert K. Wayne
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA
| | - Kirk E. Lohmueller
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095, USA
- Interdepartmental Program in Bioinformatics, University of California, Los Angeles, CA 90095, USA
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA
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5
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Coutellec MA, Chaumot A, Sucré E. Neglected impacts of plant protection products on invertebrate aquatic biodiversity: a focus on eco-evolutionary processes. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024:10.1007/s11356-024-32767-3. [PMID: 38459285 DOI: 10.1007/s11356-024-32767-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 02/29/2024] [Indexed: 03/10/2024]
Abstract
The application of plant protection products (PPPs) may have delayed and long-term non-intentional impacts on aquatic invertebrates inhabiting agricultural landscapes. Such effects may induce population responses based on developmental and transgenerational plasticity, selection of genetic resistance, as well as increased extirpation risks associated with random genetic drift. While the current knowledge on such effects of PPPs is still scarce in non-target aquatic invertebrate species, evidences are accumulating that support the need for consideration of evolutionary components of the population response to PPPs in standard procedures of risk assessment. This mini-review, as part of a contribution to the collective scientific assessment on PPP impacts on biodiversity and ecosystem services performed in the period 2020-2022, presents a brief survey of the current results published on the subject, mainly in freshwater crustaceans, and proposes some research avenues and strategies that we feel relevant to fill this gap.
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Affiliation(s)
- Marie-Agnès Coutellec
- DECOD (Ecosystem Dynamics and Sustainability), INRAE, L'Institut Agro, IFREMER, 35042, Rennes, France.
| | - Arnaud Chaumot
- Laboratoire d'écotoxicologie, INRAE, UR RiverLy, 69625, Villeurbanne, France
| | - Elliott Sucré
- MARBEC (MARine Biodiversity, Exploitation and Conservation), Université de Montpellier, CNRS, Ifremer, IRD, 34000, Montpellier, France
- Université de Mayotte, Dembeni, 97660, Mayotte, France
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6
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Charlesworth B. The fitness consequences of genetic divergence between polymorphic gene arrangements. Genetics 2024; 226:iyad218. [PMID: 38147527 PMCID: PMC11090464 DOI: 10.1093/genetics/iyad218] [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: 10/15/2023] [Revised: 12/15/2023] [Accepted: 12/20/2023] [Indexed: 12/28/2023] Open
Abstract
Inversions restrict recombination when heterozygous with standard arrangements, but often have few noticeable phenotypic effects. Nevertheless, there are several examples of inversions that can be maintained polymorphic by strong selection under laboratory conditions. A long-standing model for the source of such selection is divergence between arrangements with respect to recessive or partially recessive deleterious mutations, resulting in a selective advantage to heterokaryotypic individuals over homokaryotypes. This paper uses a combination of analytical and numerical methods to investigate this model, for the simple case of an autosomal inversion with multiple independent nucleotide sites subject to mildly deleterious mutations. A complete lack of recombination in heterokaryotypes is assumed, as well as constancy of the frequency of the inversion over space and time. It is shown that a significantly higher mutational load will develop for the less frequent arrangement. A selective advantage to heterokaryotypes is only expected when the two alternative arrangements are nearly equal in frequency, so that their mutational loads are very similar in size. The effects of some Drosophila pseudoobscura polymorphic inversions on fitness traits seem to be too large to be explained by this process, although it may contribute to some of the observed effects. Several population genomic statistics can provide evidence for signatures of a reduced efficacy of selection associated with the rarer of two arrangements, but there is currently little published data that are relevant to the theoretical predictions.
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Affiliation(s)
- Brian Charlesworth
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
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Dickel L, Arcese P, Keller LF, Nietlisbach P, Goedert D, Jensen H, Reid JM. Multigenerational Fitness Effects of Natural Immigration Indicate Strong Heterosis and Epistatic Breakdown in a Wild Bird Population. Am Nat 2024; 203:411-431. [PMID: 38358807 DOI: 10.1086/728669] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
AbstractThe fitness of immigrants and their descendants produced within recipient populations fundamentally underpins the genetic and population dynamic consequences of immigration. Immigrants can in principle induce contrasting genetic effects on fitness across generations, reflecting multifaceted additive, dominance, and epistatic effects. Yet full multigenerational and sex-specific fitness effects of regular immigration have not been quantified within naturally structured systems, precluding inference on underlying genetic architectures and population outcomes. We used four decades of song sparrow (Melospiza melodia) life history and pedigree data to quantify fitness of natural immigrants, natives, and their F1, F2, and backcross descendants and test for evidence of nonadditive genetic effects. Values of key fitness components (including adult lifetime reproductive success and zygote survival) of F1 offspring of immigrant-native matings substantially exceeded their parent mean, indicating strong heterosis. Meanwhile, F2 offspring of F1-F1 matings had notably low values, indicating surprisingly strong epistatic breakdown. Furthermore, magnitudes of effects varied among fitness components and differed between female and male descendants. These results demonstrate that strong nonadditive genetic effects on fitness can arise within weakly structured and fragmented populations experiencing frequent natural immigration. Such effects will substantially affect the net degree of effective gene flow and resulting local genetic introgression and adaptation.
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Soto TY, Rojas-Gutierrez JD, Oakley CG. Can heterosis and inbreeding depression explain the maintenance of outcrossing in a cleistogamous perennial? AMERICAN JOURNAL OF BOTANY 2023; 110:e16240. [PMID: 37672596 DOI: 10.1002/ajb2.16240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 08/17/2023] [Accepted: 08/18/2023] [Indexed: 09/08/2023]
Abstract
PREMISE What maintains mixed mating is an evolutionary enigma. Cleistogamy-the production of both potentially outcrossing chasmogamous and obligately selfing cleistogamous flowers on the same individual plant-is an excellent system to study the costs of selfing. Inbreeding depression can prevent the evolution of greater selfing within populations, and heterosis in crosses between populations may further tip the balance in favor of outcrossing. Few empirical estimates of inbreeding depression and heterosis in the same system exist for cleistogamous species. METHODS We investigate the potential costs of selfing by quantifying inbreeding depression and heterosis in three populations of the cleistogamous perennial Ruellia humilis Nutt (Acanthaceae). We performed three types of hand-pollinations-self, outcross-within, and outcross-between populations-and measured seed number, germination, total flower production, and estimated cumulative fitness for the resulting progeny in a greenhouse experiment. RESULTS We found moderate inbreeding depression for cumulative fitness (<30%) in two populations, but outbreeding depression for crosses within a third population (-26%). For between-population crosses, there was weak to modest heterosis (11-47%) in two of the population combinations, but modest to strong outbreeding depression (-21 to -71%) in the other four combinations. CONCLUSIONS Neither inbreeding depression nor heterosis was of sufficient magnitude to explain the continued production of chasmogamous flowers given the relative energetic advantage of cleistogamous flowers previously estimated for these populations. Outbreeding depression either within or between populations makes the maintenance of chasmogamous flowers even harder to explain. More information is needed on the genetic basis of cleistogamy to resolve this conundrum.
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Affiliation(s)
- Tatyana Y Soto
- Department of Botany and Plant Pathology and the Center for Plant Biology, Purdue University, West Lafayette, IN, USA
| | - Juan Diego Rojas-Gutierrez
- Department of Botany and Plant Pathology and the Center for Plant Biology, Purdue University, West Lafayette, IN, USA
| | - Christopher G Oakley
- Department of Botany and Plant Pathology and the Center for Plant Biology, Purdue University, West Lafayette, IN, USA
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Burnett HA, Bieker VC, Le Moullec M, Peeters B, Rosvold J, Pedersen ÅØ, Dalén L, Loe LE, Jensen H, Hansen BB, Martin MD. Contrasting genomic consequences of anthropogenic reintroduction and natural recolonization in high-arctic wild reindeer. Evol Appl 2023; 16:1531-1548. [PMID: 37752961 PMCID: PMC10519417 DOI: 10.1111/eva.13585] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 07/27/2023] [Accepted: 08/01/2023] [Indexed: 09/28/2023] Open
Abstract
Anthropogenic reintroduction can supplement natural recolonization in reestablishing a species' distribution and abundance. However, both reintroductions and recolonizations can give rise to founder effects that reduce genetic diversity and increase inbreeding, potentially causing the accumulation of genetic load and reduced fitness. Most current populations of the endemic high-arctic Svalbard reindeer (Rangifer tarandus platyrhynchus) originate from recent reintroductions or recolonizations following regional extirpations due to past overharvesting. We investigated and compared the genomic consequences of these two paths to reestablishment using whole-genome shotgun sequencing of 100 Svalbard reindeer across their range. We found little admixture between reintroduced and natural populations. Two reintroduced populations, each founded by 12 individuals around four decades (i.e. 8 reindeer generations) ago, formed two distinct genetic clusters. Compared to the source population, these populations showed only small decreases in genome-wide heterozygosity and increases in inbreeding and lengths of runs of homozygosity. In contrast, the two naturally recolonized populations without admixture possessed much lower heterozygosity, higher inbreeding and longer runs of homozygosity, possibly caused by serial population founder effects and/or fewer or more genetically related founders than in the reintroduction events. Naturally recolonized populations can thus be more vulnerable to the accumulation of genetic load than reintroduced populations. This suggests that in some organisms even small-scale reintroduction programs based on genetically diverse source populations can be more effective than natural recolonization in establishing genetically diverse populations. These findings warrant particular attention in the conservation and management of populations and species threatened by habitat fragmentation and loss.
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Affiliation(s)
- Hamish A. Burnett
- Centre for Biodiversity Dynamics, Department of BiologyNorwegian University of Science and Technology (NTNU)TrondheimNorway
- Department of Natural History, NTNU University MuseumNorwegian University of Science and Technology (NTNU)TrondheimNorway
| | - Vanessa C. Bieker
- Centre for Biodiversity Dynamics, Department of BiologyNorwegian University of Science and Technology (NTNU)TrondheimNorway
- Department of Natural History, NTNU University MuseumNorwegian University of Science and Technology (NTNU)TrondheimNorway
| | - Mathilde Le Moullec
- Centre for Biodiversity Dynamics, Department of BiologyNorwegian University of Science and Technology (NTNU)TrondheimNorway
| | - Bart Peeters
- Centre for Biodiversity Dynamics, Department of BiologyNorwegian University of Science and Technology (NTNU)TrondheimNorway
| | - Jørgen Rosvold
- Department of Terrestrial BiodiversityNorwegian Institute for Nature Research (NINA)TrondheimNorway
| | | | - Love Dalén
- Centre for PalaeogeneticsStockholmSweden
- Department of Bioinformatics and GeneticsSwedish Museum of Natural HistoryStockholmSweden
- Department of ZoologyStockholm UniversityStockholmSweden
| | - Leif Egil Loe
- Faculty of Environmental Sciences and Natural Resource ManagementNorwegian University of Life SciencesAasNorway
| | - Henrik Jensen
- Centre for Biodiversity Dynamics, Department of BiologyNorwegian University of Science and Technology (NTNU)TrondheimNorway
| | - Brage B. Hansen
- Centre for Biodiversity Dynamics, Department of BiologyNorwegian University of Science and Technology (NTNU)TrondheimNorway
- Department of Terrestrial EcologyNorwegian Institute for Nature Research (NINA)TrondheimNorway
| | - Michael D. Martin
- Centre for Biodiversity Dynamics, Department of BiologyNorwegian University of Science and Technology (NTNU)TrondheimNorway
- Department of Natural History, NTNU University MuseumNorwegian University of Science and Technology (NTNU)TrondheimNorway
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Surina B, Balant M, Glasnović P, Radosavljević I, Fišer Ž, Fujs N, Castro S. Population size as a major determinant of mating system and population genetic differentiation in a narrow endemic chasmophyte. BMC PLANT BIOLOGY 2023; 23:383. [PMID: 37553615 PMCID: PMC10411015 DOI: 10.1186/s12870-023-04384-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Accepted: 07/18/2023] [Indexed: 08/10/2023]
Abstract
BACKGROUND Mating system is one of the major determinants of intra- and interspecific genetic structure, but may vary within and between plant populations. Our study model included all known populations of Moehringia tommasinii (Caryophyllaceae), a narrow endemic plant inhabiting rock crevices in the northwestern Adriatic, and some populations of co-occurring and widespread M. muscosa, an ecologically divergent relative with an overlapping flowering period. We performed reciprocal crosses within and between taxa and used molecular markers to assess the extent of gene flow within and between populations and taxa. Using coefficient of inbreeding, population size, seed weight, pollen-to-ovule ratio, and flower display size, we also looked for evidence of a selfing syndrome. RESULTS A surprisingly high variation in mating systems was observed among populations of M. tommasinii. These populations exhibited genetic structuring, with their size positively correlated with both seed weight and pollen production. Although a selfing syndrome could not be confirmed as the majority of selfing resulted from allogamous treatments, the occurrence of selfing was notable. In the presence of M. muscosa, at a site where both species coexist closely, a distinct pattern of fruit production was observed in M. tommasinii following various pollination treatments. Molecular and morphometric data provided evidence of hybridization followed by local extinction at this site. CONCLUSIONS Population size proved to be the most important factor affecting the mating system in genetically structured populations of M. tommasinii. Lighter seeds and lower pollen production observed in populations with pronounced selfing do not provide enough evidence for the selfing syndrome. Detected gene flow between M. tommasinii and the sympatric M. muscosa suggested weak reproductive barriers between the taxa, which could pose a conservation problems for the former species. Hybridization leading to local extinction may also resulted in floral polymorphism and disruption of mating patterns of M. tommasinii.
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Affiliation(s)
- Boštjan Surina
- Natural History Museum Rijeka, Lorenzov prolaz 1, 51000, Rijeka, Croatia.
- Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Glagoljaška 8, 6000, Koper, Slovenia.
| | - Manica Balant
- Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Glagoljaška 8, 6000, Koper, Slovenia
- Institut Botànic de Barcelona (IBB, CSIC-Ajuntament de Barcelona), Passeig del Migdia s.n., Parc de Montjuïc, 08038, Barcelona, Spain
| | - Peter Glasnović
- Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Glagoljaška 8, 6000, Koper, Slovenia
| | - Ivan Radosavljević
- Division of Botany, Department of Biology, Faculty of Science, University of Zagreb, Marulićev trg 9a, 10000, Zagreb, Croatia
- Centre of Excellence for Biodiversity and Molecular Plant Breeding, Svetošimunska cesta 25, 10000, Zagreb, Croatia
| | - Živa Fišer
- Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Glagoljaška 8, 6000, Koper, Slovenia
| | - Nataša Fujs
- Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Glagoljaška 8, 6000, Koper, Slovenia
| | - Sílvia Castro
- Centre for Functional Ecology-Science for People & the Planet, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456, Coimbra, Portugal
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11
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Hudson CM, Cuenca Cambronero M, Moosmann M, Narwani A, Spaak P, Seehausen O, Matthews B. Environmentally independent selection for hybrids between divergent freshwater stickleback lineages in semi-natural ponds. J Evol Biol 2023; 36:1166-1184. [PMID: 37394735 DOI: 10.1111/jeb.14194] [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: 11/16/2022] [Revised: 05/03/2023] [Accepted: 05/31/2023] [Indexed: 07/04/2023]
Abstract
Hybridization following secondary contact of genetically divergent populations can influence the range expansion of invasive species, though specific outcomes depend on the environmental dependence of hybrid fitness. Here, using two genetically and ecologically divergent threespine stickleback lineages that differ in their history of freshwater colonization, we estimate fitness variation of parental lineages and hybrids in semi-natural freshwater ponds with contrasting histories of nutrient loading. In our experiment, we found that fish from the older freshwater lineage (Lake Geneva) and hybrids outperformed fish from the younger freshwater lineage (Lake Constance) in terms of both growth and survival, regardless of the environmental context of our ponds. Across all ponds, hybrids exhibited the highest survival. Although wild-caught adult populations differed in their functional and defence morphology, it is unclear which of these traits underlie the fitness differences observed among juveniles in our experiment. Overall, our work suggests that when hybrid fitness is insensitive to environmental conditions, as observed here, introgression may promote population expansion into unoccupied habitats and accelerate invasion success.
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Affiliation(s)
- Cameron Marshall Hudson
- Department of Fish Ecology and Evolution, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Center of Ecology, Evolution and Biochemistry, Lucerne, Switzerland
- Division of Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
- Department of Aquatic Ecology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Zürich, Switzerland
| | - Maria Cuenca Cambronero
- Department of Fish Ecology and Evolution, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Center of Ecology, Evolution and Biochemistry, Lucerne, Switzerland
- Aquatic Ecology Group, University of Vic, Central University of Catalonia, Vic, Spain
| | - Marvin Moosmann
- Department of Fish Ecology and Evolution, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Center of Ecology, Evolution and Biochemistry, Lucerne, Switzerland
- Division of Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - Anita Narwani
- Department of Aquatic Ecology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Zürich, Switzerland
| | - Piet Spaak
- Department of Aquatic Ecology, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Zürich, Switzerland
| | - Ole Seehausen
- Department of Fish Ecology and Evolution, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Center of Ecology, Evolution and Biochemistry, Lucerne, Switzerland
- Division of Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - Blake Matthews
- Department of Fish Ecology and Evolution, Eawag, Swiss Federal Institute of Aquatic Science and Technology, Center of Ecology, Evolution and Biochemistry, Lucerne, Switzerland
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Horne JB, Frey A, Gaos AR, Martin S, Dutton PH. Non-random mating within an Island rookery of Hawaiian hawksbill turtles: demographic discontinuity at a small coastline scale. ROYAL SOCIETY OPEN SCIENCE 2023; 10:221547. [PMID: 37206959 PMCID: PMC10189603 DOI: 10.1098/rsos.221547] [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: 12/01/2022] [Accepted: 04/26/2023] [Indexed: 05/21/2023]
Abstract
Hawksbill sea turtles (Eretmochelys imbricata) from the Hawaiian archipelago form a small and genetically isolated population, consisting of only a few tens of individuals breeding annually. Most females nest on the island of Hawai'i, but little is known about the demographics of this rookery. This study used genetic relatedness, inferred from 135 microhaplotype markers, to determine breeding sex-ratios, estimate female nesting frequency and assess relationships between individuals nesting on different beaches. Samples were collected during the 2017 nesting season and final data included 13 nesting females and 1002 unhatched embryos, salvaged from 41 nests, of which 13 had no observed mother. Results show that most females used a single nesting beach laying 1-5 nests each. From female and offspring alleles, the paternal genotypes of 12 breeding males were reconstructed and many showed high relatedness to their mates. Pairwise relatedness of offspring revealed one instance of polygyny but otherwise suggested a 1 : 1 breeding-sex ratio. Relatedness analysis and spatial-autocorrelation of genotypes indicate that turtles from different nesting areas do not regularly interbreed, suggesting that strong natal homing tendencies in both sexes result in non-random mating across the study area. Complexes of nearby nesting beaches also showed unique patterns of inbreeding across loci, further indicating that Hawaiian hawksbill turtles have demographically discontinuous nesting populations separated by only tens of km.
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Affiliation(s)
- John B. Horne
- Southwest Fisheries Science Center, NOAA-Fisheries, La Jolla, CA, USA
| | - Amy Frey
- Southwest Fisheries Science Center, NOAA-Fisheries, La Jolla, CA, USA
| | - Alexander R. Gaos
- Pacific Islands Fisheries Science Center, NOAA-Fisheries, Honolulu, HI, USA
| | - Summer Martin
- Pacific Islands Fisheries Science Center, NOAA-Fisheries, Honolulu, HI, USA
| | - Peter H. Dutton
- Southwest Fisheries Science Center, NOAA-Fisheries, La Jolla, CA, USA
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13
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Robinson J, Kyriazis CC, Yuan SC, Lohmueller KE. Deleterious Variation in Natural Populations and Implications for Conservation Genetics. Annu Rev Anim Biosci 2023; 11:93-114. [PMID: 36332644 PMCID: PMC9933137 DOI: 10.1146/annurev-animal-080522-093311] [Citation(s) in RCA: 28] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Deleterious mutations decrease reproductive fitness and are ubiquitous in genomes. Given that many organisms face ongoing threats of extinction, there is interest in elucidating the impact of deleterious variation on extinction risk and optimizing management strategies accounting for such mutations. Quantifying deleterious variation and understanding the effects of population history on deleterious variation are complex endeavors because we do not know the strength of selection acting on each mutation. Further, the effect of demographic history on deleterious mutations depends on the strength of selection against the mutation and the degree of dominance. Here we clarify how deleterious variation can be quantified and studied in natural populations. We then discuss how different demographic factors, such as small population size, nonequilibrium population size changes, inbreeding, and gene flow, affect deleterious variation. Lastly, we provide guidance on studying deleterious variation in nonmodel populations of conservation concern.
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Affiliation(s)
- Jacqueline Robinson
- Institute for Human Genetics, University of California, San Francisco, California, USA;
| | - Christopher C Kyriazis
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, USA; , ,
| | - Stella C Yuan
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, USA; , ,
| | - Kirk E Lohmueller
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, USA; , , .,Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California, USA
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14
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Mating system and speciation I: Accumulation of genetic incompatibilities in allopatry. PLoS Genet 2022; 18:e1010353. [PMID: 36520924 PMCID: PMC9799327 DOI: 10.1371/journal.pgen.1010353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Revised: 12/29/2022] [Accepted: 11/25/2022] [Indexed: 12/23/2022] Open
Abstract
Self-fertilisation is widespread among hermaphroditic species across the tree of life. Selfing has many consequences on the genetic diversity and the evolutionary dynamics of populations, which may in turn affect macroevolutionary processes such as speciation. On the one hand, because selfing increases genetic drift and reduces migration rate among populations, it may be expected to promote speciation. On the other hand, because selfing reduces the efficacy of selection, it may be expected to hamper ecological speciation. To better understand under which conditions and in which direction selfing affects the build-up of reproductive isolation, an explicit population genetics model is required. Here, we focus on the interplay between genetic drift, selection and genetic linkage by studying speciation without gene flow. We test how fast populations with different rates of selfing accumulate mutations leading to genetic incompatibilities. When speciation requires populations to pass through a fitness valley caused by underdominant and compensatory mutations, selfing reduces the depth and/or breadth of the valley, and thus overall facilitates the fixation of incompatibilities. When speciation does not require populations to pass through a fitness valley, as for Bateson-Dobzhanzky-Muller incompatibilities (BDMi), the lower effective population size and higher genetic linkage in selfing populations both facilitate the fixation of incompatibilities. Interestingly, and contrary to intuitive expectations, local adaptation does not always accelerate the fixation of incompatibilities in outcrossing relative to selfing populations. Our work helps to clarify how incompatibilities accumulate in selfing vs. outcrossing lineages, and has repercussions on the pace of speciation as well as on the genetic architecture of reproductive isolation.
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15
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Maier PA, Vandergast AG, Ostoja SM, Aguilar A, Bohonak AJ. Landscape genetics of a sub-alpine toad: climate change predicted to induce upward range shifts via asymmetrical migration corridors. Heredity (Edinb) 2022; 129:257-272. [PMID: 36076071 PMCID: PMC9613655 DOI: 10.1038/s41437-022-00561-x] [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: 05/16/2022] [Revised: 08/24/2022] [Accepted: 08/25/2022] [Indexed: 11/08/2022] Open
Abstract
Climate change is expected to have a major hydrological impact on the core breeding habitat and migration corridors of many amphibians in the twenty-first century. The Yosemite toad (Anaxyrus canorus) is a species of meadow-specializing amphibian endemic to the high-elevation Sierra Nevada Mountains of California. Despite living entirely on federal lands, it has recently faced severe extirpations, yet our understanding of climatic influences on population connectivity is limited. In this study, we used a previously published double-digest RADseq dataset along with numerous remotely sensed habitat features in a landscape genetics framework to answer two primary questions in Yosemite National Park: (1) Which fine-scale climate, topographic, soil, and vegetation features most facilitate meadow connectivity? (2) How is climate change predicted to influence both the magnitude and net asymmetry of genetic migration? We developed an approach for simultaneously modeling multiple toad migration paths, akin to circuit theory, except raw environmental features can be separately considered. Our workflow identified the most likely migration corridors between meadows and used the unique cubist machine learning approach to fit and forecast environmental models of connectivity. We identified the permuted modeling importance of numerous snowpack-related features, such as runoff and groundwater recharge. Our results highlight the importance of considering phylogeographic structure, and asymmetrical migration in landscape genetics. We predict an upward elevational shift for this already high-elevation species, as measured by the net vector of anticipated genetic movement, and a north-eastward shift in species distribution via the network of genetic migration corridors across the park.
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Affiliation(s)
- Paul A Maier
- Department of Biology, San Diego State University, 5500 Campanile Dr., San Diego, CA, 92182, USA.
- FamilyTreeDNA, Gene by Gene, 1445 N Loop W, Houston, TX, 77008, USA.
| | - Amy G Vandergast
- U.S. Geological Survey, Western Ecological Research Center, San Diego Field Station, San Diego, CA, 92101, USA
| | - Steven M Ostoja
- USDA California Climate Hub, Agricultural Research Service, John Muir Institute of the Environment, University of California, Davis, 1 Shields Ave., Davis, CA, 95616, USA
| | - Andres Aguilar
- Department of Biological Sciences, California State University, Los Angeles, 5151 State University Dr., Los Angeles, CA, 90032, USA
| | - Andrew J Bohonak
- Department of Biology, San Diego State University, 5500 Campanile Dr., San Diego, CA, 92182, USA
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16
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Genetic load: genomic estimates and applications in non-model animals. Nat Rev Genet 2022; 23:492-503. [PMID: 35136196 DOI: 10.1038/s41576-022-00448-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/10/2022] [Indexed: 12/11/2022]
Abstract
Genetic variation, which is generated by mutation, recombination and gene flow, can reduce the mean fitness of a population, both now and in the future. This 'genetic load' has been estimated in a wide range of animal taxa using various approaches. Advances in genome sequencing and computational techniques now enable us to estimate the genetic load in populations and individuals without direct fitness estimates. Here, we review the classic and contemporary literature of genetic load. We describe approaches to quantify the genetic load in whole-genome sequence data based on evolutionary conservation and annotations. We show that splitting the load into its two components - the realized load (or expressed load) and the masked load (or inbreeding load) - can improve our understanding of the population genetics of deleterious mutations.
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17
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Thompson KA, Peichel CL, Rennison DJ, McGee MD, Albert AYK, Vines TH, Greenwood AK, Wark AR, Brandvain Y, Schumer M, Schluter D. Analysis of ancestry heterozygosity suggests that hybrid incompatibilities in threespine stickleback are environment dependent. PLoS Biol 2022; 20:e3001469. [PMID: 35007278 PMCID: PMC8746713 DOI: 10.1371/journal.pbio.3001469] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 11/04/2021] [Indexed: 12/25/2022] Open
Abstract
Hybrid incompatibilities occur when interactions between opposite ancestry alleles at different loci reduce the fitness of hybrids. Most work on incompatibilities has focused on those that are "intrinsic," meaning they affect viability and sterility in the laboratory. Theory predicts that ecological selection can also underlie hybrid incompatibilities, but tests of this hypothesis using sequence data are scarce. In this article, we compiled genetic data for F2 hybrid crosses between divergent populations of threespine stickleback fish (Gasterosteus aculeatus L.) that were born and raised in either the field (seminatural experimental ponds) or the laboratory (aquaria). Because selection against incompatibilities results in elevated ancestry heterozygosity, we tested the prediction that ancestry heterozygosity will be higher in pond-raised fish compared to those raised in aquaria. We found that ancestry heterozygosity was elevated by approximately 3% in crosses raised in ponds compared to those raised in aquaria. Additional analyses support a phenotypic basis for incompatibility and suggest that environment-specific single-locus heterozygote advantage is not the cause of selection on ancestry heterozygosity. Our study provides evidence that, in stickleback, a coarse-albeit indirect-signal of environment-dependent hybrid incompatibility is reliably detectable and suggests that extrinsic incompatibilities can evolve before intrinsic incompatibilities.
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Affiliation(s)
- Ken A. Thompson
- Department of Zoology & Biodiversity Research Centre, University of British Columbia, Canada
| | - Catherine L. Peichel
- Division of Evolutionary Ecology, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - Diana J. Rennison
- Division of Biological Sciences, University of California San Diego, San Diego, California, United States of America
| | - Matthew D. McGee
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | | | - Timothy H. Vines
- DataSeer Research Data Services, Vancouver, British Columbia, Canada
| | | | - Abigail R. Wark
- Harvard Medical School, Cambridge, Massachusetts, United States of America
| | - Yaniv Brandvain
- Department of Plant and Microbial Biology, University of Minnesota, Saint Paul, Minnesota, United States of America
| | - Molly Schumer
- Department of Biology, Stanford University, Stanford, California, United States of America
- Howard Hughes Medical Institute, Maryland, United States of America
| | - Dolph Schluter
- Department of Zoology & Biodiversity Research Centre, University of British Columbia, Canada
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18
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Foote AD, Hooper R, Alexander A, Baird RW, Baker CS, Ballance L, Barlow J, Brownlow A, Collins T, Constantine R, Dalla Rosa L, Davison NJ, Durban JW, Esteban R, Excoffier L, Martin SLF, Forney KA, Gerrodette T, Gilbert MTP, Guinet C, Hanson MB, Li S, Martin MD, Robertson KM, Samarra FIP, de Stephanis R, Tavares SB, Tixier P, Totterdell JA, Wade P, Wolf JBW, Fan G, Zhang Y, Morin PA. Runs of homozygosity in killer whale genomes provide a global record of demographic histories. Mol Ecol 2021; 30:6162-6177. [PMID: 34416064 DOI: 10.1111/mec.16137] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 08/10/2021] [Accepted: 08/18/2021] [Indexed: 02/06/2023]
Abstract
Runs of homozygosity (ROH) occur when offspring inherit haplotypes that are identical by descent from each parent. Length distributions of ROH are informative about population history; specifically, the probability of inbreeding mediated by mating system and/or population demography. Here, we investigated whether variation in killer whale (Orcinus orca) demographic history is reflected in genome-wide heterozygosity and ROH length distributions, using a global data set of 26 genomes representative of geographic and ecotypic variation in this species, and two F1 admixed individuals with Pacific-Atlantic parentage. We first reconstructed demographic history for each population as changes in effective population size through time using the pairwise sequential Markovian coalescent (PSMC) method. We found a subset of populations declined in effective population size during the Late Pleistocene, while others had more stable demography. Genomes inferred to have undergone ancestral declines in effective population size, were autozygous at hundreds of short ROH (<1 Mb), reflecting high background relatedness due to coalescence of haplotypes deep within the pedigree. In contrast, longer and therefore younger ROH (>1.5 Mb) were found in low latitude populations, and populations of known conservation concern. These include a Scottish killer whale, for which 37.8% of the autosomes were comprised of ROH >1.5 Mb in length. The fate of this population, in which only two adult males have been sighted in the past five years, and zero fecundity over the last two decades, may be inextricably linked to its demographic history and consequential inbreeding depression.
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Affiliation(s)
- Andrew D Foote
- Department of Natural History, NTNU University Museum, Norwegian University of Science and Technology (NTNU, Trondheim, Norway.,Molecular Ecology and Fisheries Genetics Laboratory, School of Biological Sciences, Bangor University, Bangor, Gwynedd, UK.,CMPG, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - Rebecca Hooper
- University of Exeter, Penryn Campus, Penryn, Cornwall, UK
| | - Alana Alexander
- Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | | | - Charles Scott Baker
- Marine Mammal Institute, Oregon State University, Newport, Oregon, USA.,School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Lisa Ballance
- Marine Mammal Institute, Oregon State University, Newport, Oregon, USA.,Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, La Jolla, California, USA
| | - Jay Barlow
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, La Jolla, California, USA
| | - Andrew Brownlow
- Scottish Marine Animal Stranding Scheme, Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Tim Collins
- Ocean Giants Program, Wildlife Conservation Society, New York City, New York
| | | | - Luciano Dalla Rosa
- Laboratório de Ecologia e Conservação da Megafauna Marinha, Instituto de Oceanografia, Universidade Federal do Rio Grande, Rio Grande, Brazil
| | - Nicholas J Davison
- Scottish Marine Animal Stranding Scheme, Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - John W Durban
- Marine Mammal Institute, Oregon State University, Newport, Oregon, USA.,Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, La Jolla, California, USA
| | - Ruth Esteban
- CIRCE, Conservation, Information and Research on Cetaceans, Algeciras, Spain
| | - Laurent Excoffier
- CMPG, Institute of Ecology and Evolution, University of Bern, Bern, Switzerland
| | - Sarah L Fordyce Martin
- Department of Natural History, NTNU University Museum, Norwegian University of Science and Technology (NTNU, Trondheim, Norway
| | - Karin A Forney
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Moss Landing, California, USA.,Moss Landing Marine Laboratories, San Jose State University, Moss Landing, California, USA
| | - Tim Gerrodette
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, La Jolla, California, USA
| | - M Thomas P Gilbert
- Department of Natural History, NTNU University Museum, Norwegian University of Science and Technology (NTNU, Trondheim, Norway.,Section for Evolutionary Genomics, The GLOBE Institute, University of Copenhagen, Copenhagen, Denmark
| | - Christophe Guinet
- UMR 7372 La Rochelle Université - CNRS, Centre d'Etudes Biologiques de Chizé (CEBC), Villiers-en-Bois, France
| | - M Bradley Hanson
- National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Northwest Fisheries Science Center, Seattle, Washington, USA
| | - Songhai Li
- Marine Mammal and Marine Bioacoustics Laboratory, Institute of Deep-Sea Science and Engineering, Chinese Academy of Science, Sanya, China
| | - Michael D Martin
- Department of Natural History, NTNU University Museum, Norwegian University of Science and Technology (NTNU, Trondheim, Norway
| | - Kelly M Robertson
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, La Jolla, California, USA
| | - Filipa I P Samarra
- University of Iceland's Institute of Research Centres, Vestmannaeyjar, Iceland
| | - Renaud de Stephanis
- CIRCE, Conservation, Information and Research on Cetaceans, Algeciras, Spain
| | - Sara B Tavares
- Scottish Oceans Institute, East Sands, University of St. Andrews, St. Andrews, UK.,Cetacean Research Program, Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, Canada
| | - Paul Tixier
- UMR 7372 La Rochelle Université - CNRS, Centre d'Etudes Biologiques de Chizé (CEBC), Villiers-en-Bois, France.,MARBEC Université de Montpellier-CNRS-IFREMER-IRD, Sète, France
| | | | - Paul Wade
- National Marine Mammal Laboratory, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Alaska Fisheries Science Center, Seattle, Washington, USA
| | - Jochen B W Wolf
- Section of Evolutionary Biology, Department of Biology II, Ludwig Maximilian University of Munich, Planegg-Martinsried, Germany
| | - Guangyi Fan
- BGI-Qingdao, BGI-Shenzhen, Qingdao, China.,BGI-Shenzhen, Shenzhen, China.,China National GeneBank, BGI-Shenzhen, Shenzhen, China
| | - Yaolei Zhang
- BGI-Qingdao, BGI-Shenzhen, Qingdao, China.,Translational Immunology group, Department of Biotechnology and Biomedicine, Technical University of Denmark, Lyngby, Denmark
| | - Phillip A Morin
- Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, La Jolla, California, USA
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19
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Salgueiro PA, Valerio F, Silva C, Mira A, Rabaça JE, Santos SM. Multispecies landscape functional connectivity enhances local bird species' diversity in a highly fragmented landscape. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2021; 284:112066. [PMID: 33561758 DOI: 10.1016/j.jenvman.2021.112066] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 12/23/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
Local species assemblages are likely the result of habitat and landscape filtering. However, there is still limited knowledge on how landscape functional connectivity complements habitat attributes in mediating local species assemblages in real-world fragmented landscapes. In this study, we set up a non-manipulative experimental design in a standard production forest to demonstrate how functional connectivity determines the spatial distribution of a bird community. We test single- and multispecies spatially explicit, landscape functional connectivity models framed within the circuit theory, considering also patch attributes describing habitat size and quality, to weight their effects on species occurrence and community assemblage. We found that single-species functional connectivity effects contributed positively for occurrence of each species. However, they rarely provided competing alternatives in predicting community parameters when compared to multispecies connectivity models. Incorporating multispecies connectivity showed more consistent effects for all community parameters, than single-species models, since the overlap between species' dispersal abilities in the landscape shows poor agreement. Habitat size and quality, though less important, were also determinant in explaining community parameters while possibly relating to the provision of suitable nesting and foraging conditions. Both habitat and landscape filters concur to govern community assembly, though likely influencing different processes: while landscape connectivity determines which species can reach a patch, habitat quality determines which species settle in the patch. Our results also suggest that surrogating multispecies connectivity from single species has potential to source bias by assuming species perceive landscape and its barriers similarly. Inference on this issue must be gathered from as much species as possible.
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Affiliation(s)
- Pedro A Salgueiro
- UBC - Conservation Biology Lab, Portugal; LabOr - Laboratory of Ornithology, Portugal; Department of Biology, University of Évora. Mitra, 7002-554, Évora, Portugal.
| | - Francesco Valerio
- UBC - Conservation Biology Lab, Portugal; CIBIO-UE - Research Center in Biodiversity and Genetic Resources, Pole of Évora, Portugal; Department of Biology, University of Évora. Mitra, 7002-554, Évora, Portugal.
| | - Carmo Silva
- UBC - Conservation Biology Lab, Portugal; MED-Mediterranean Institute for Agriculture, Environment and Development, Instituto de Investigação e Formação Avançada, USA; Department of Biology, University of Évora. Mitra, 7002-554, Évora, Portugal.
| | - António Mira
- UBC - Conservation Biology Lab, Portugal; MED-Mediterranean Institute for Agriculture, Environment and Development, Instituto de Investigação e Formação Avançada, USA; Department of Biology, University of Évora. Mitra, 7002-554, Évora, Portugal.
| | - João E Rabaça
- LabOr - Laboratory of Ornithology, Portugal; MED-Mediterranean Institute for Agriculture, Environment and Development, Instituto de Investigação e Formação Avançada, USA; Department of Biology, University of Évora. Mitra, 7002-554, Évora, Portugal.
| | - Sara M Santos
- UBC - Conservation Biology Lab, Portugal; MED-Mediterranean Institute for Agriculture, Environment and Development, Instituto de Investigação e Formação Avançada, USA; Department of Biology, University of Évora. Mitra, 7002-554, Évora, Portugal.
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20
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Waller DM. Addressing Darwin's dilemma: Can pseudo-overdominance explain persistent inbreeding depression and load? Evolution 2021; 75:779-793. [PMID: 33598971 DOI: 10.1111/evo.14189] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 01/06/2021] [Accepted: 01/30/2021] [Indexed: 01/01/2023]
Abstract
Darwin spent years investigating the effects of self-fertilization, concluding that "nature abhors perpetual self-fertilization." Given that selection purges inbred populations of strongly deleterious mutations and drift fixes mild mutations, why does inbreeding depression (ID) persist in highly inbred taxa and why do no purely selfing taxa exist? Background selection, associations and interference among loci, and drift within small inbred populations all limit selection while often increasing fixation. These mechanisms help to explain why more inbred populations in most species consistently show more fixed load. This drift load is manifest in the considerable heterosis regularly observed in between-population crosses. Such heterosis results in subsequent high ID, suggesting a mechanism by which small populations could retain variation and inbreeding load. Multiple deleterious recessive mutations linked in repulsion generate pseudo-overdominance. Many tightly linked load loci could generate a balanced segregating load high enough to sustain ID over many generations. Such pseudo-overdominance blocks (or "PODs") are more likely to occur in regions of low recombination. They should also result in clear genetic signatures including genomic hotspots of heterozygosity; distinct haplotypes supporting alleles at intermediate frequency; and high linkage disequilibrium in and around POD regions. Simulation and empirical studies tend to support these predictions. Additional simulations and comparative genomic analyses should explore POD dynamics in greater detail to resolve whether PODs exist in sufficient strength and number to account for why ID and load persist within inbred lineages.
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Affiliation(s)
- Donald M Waller
- Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin, 53706
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21
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Undin M, Lockhart PJ, Hills SFK, Castro I. Genetic Rescue and the Plight of Ponui Hybrids. FRONTIERS IN CONSERVATION SCIENCE 2021. [DOI: 10.3389/fcosc.2020.622191] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Long-term sustainable and resilient populations is a key goal of conservation. How to best achieve this is controversial. There are, for instance, polarized views concerning the fitness and conservation value of hybrid populations founded through multi-origin translocations. A classic example concerns Apteryx (kiwi) in New Zealand. The A. mantelli of Ponui Island constitute a hybrid population where the birds are highly successful in their island habitat. A key dilemma for managers is understanding the reason for this success. Are the hybrid birds of Ponui Island of “no future conservation value” as recently asserted, or do they represent an outstanding example of genetic rescue and an important resource for future translocations? There has been a paradigm shift in scientific thinking concerning hybrids, but the ecological significance of admixed genomes remains difficult to assess. This limits what we can currently predict in conservation science. New understanding from genome science challenges the sufficiency of population genetic models to inform decision making and suggests instead that the contrasting outcomes of hybridization, “outbreeding depression” and “heterosis,” require understanding additional factors that modulate gene and protein expression and how these factors are influenced by the environment. We discuss these findings and the investigations that might help us to better understand the birds of Ponui, inform conservation management of kiwi and provide insight relevant for the future survival of Apteryx.
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22
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Söderquist L, Broberg A, Rosenberg V, Sletvold N. Predicting heterosis and inbreeding depression from population size and density to inform management efforts. J Appl Ecol 2020. [DOI: 10.1111/1365-2664.13643] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Linus Söderquist
- Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Uppsala Sweden
| | - Anna Broberg
- Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Uppsala Sweden
| | - Viktor Rosenberg
- Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Uppsala Sweden
| | - Nina Sletvold
- Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Uppsala Sweden
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23
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Consistent scaling of inbreeding depression in space and time in a house sparrow metapopulation. Proc Natl Acad Sci U S A 2020; 117:14584-14592. [PMID: 32513746 DOI: 10.1073/pnas.1909599117] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Inbreeding may increase the extinction risk of small populations. Yet, studies using modern genomic tools to investigate inbreeding depression in nature have been limited to single populations, and little is known about the dynamics of inbreeding depression in subdivided populations over time. Natural populations often experience different environmental conditions and differ in demographic history and genetic composition, characteristics that can affect the severity of inbreeding depression. We utilized extensive long-term data on more than 3,100 individuals from eight islands in an insular house sparrow metapopulation to examine the generality of inbreeding effects. Using genomic estimates of realized inbreeding, we discovered that inbred individuals had lower survival probabilities and produced fewer recruiting offspring than noninbred individuals. Inbreeding depression, measured as the decline in fitness-related traits per unit inbreeding, did not vary appreciably among populations or with time. As a consequence, populations with more resident inbreeding (due to their demographic history) paid a higher total fitness cost, evidenced by a larger variance in fitness explained by inbreeding within these populations. Our results are in contrast to the idea that effects of inbreeding generally depend on ecological factors and genetic differences among populations, and expand the understanding of inbreeding depression in natural subdivided populations.
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The Impact of Recessive Deleterious Variation on Signals of Adaptive Introgression in Human Populations. Genetics 2020; 215:799-812. [PMID: 32487519 PMCID: PMC7337073 DOI: 10.1534/genetics.120.303081] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 05/01/2020] [Indexed: 12/19/2022] Open
Abstract
Admixture with archaic hominins has altered the landscape of genomic variation in modern human populations. Several gene regions have been identified previously as candidates of adaptive introgression (AI) that facilitated human adaptation to specific environments. However, simulation-based studies have suggested that population genetic processes other than adaptive mutations, such as heterosis from recessive deleterious variants private to populations before admixture, can also lead to patterns in genomic data that resemble AI. The extent to which the presence of deleterious variants affect the false-positive rate and the power of current methods to detect AI has not been fully assessed. Here, we used extensive simulations under parameters relevant for human evolution to show that recessive deleterious mutations can increase the false positive rates of tests for AI compared to models without deleterious variants, especially when the recombination rates are low. We next examined candidates of AI in modern humans identified from previous studies, and show that 24 out of 26 candidate regions remain significant, even when deleterious variants are included in the null model. However, two AI candidate genes, HYAL2 and HLA, are particularly susceptible to high false positive signals of AI due to recessive deleterious mutations. These genes are located in regions of the human genome with high exon density together with low recombination rate, factors that we show increase the rate of false-positives due to recessive deleterious mutations. Although the combination of such parameters is rare in the human genome, caution is warranted in such regions, as well as in other species with more compact genomes and/or lower recombination rates. In sum, our results suggest that recessive deleterious mutations cannot account for the signals of AI in most, but not all, of the top candidates for AI in humans, suggesting they may be genuine signals of adaptation.
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Duranton M, Allal F, Valière S, Bouchez O, Bonhomme F, Gagnaire PA. The contribution of ancient admixture to reproductive isolation between European sea bass lineages. Evol Lett 2020; 4:226-242. [PMID: 32547783 PMCID: PMC7293100 DOI: 10.1002/evl3.169] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 01/02/2020] [Accepted: 03/05/2020] [Indexed: 12/20/2022] Open
Abstract
Understanding how new species arise through the progressive establishment of reproductive isolation (RI) barriers between diverging populations is a major goal in Evolutionary Biology. An important result of speciation genomics studies is that genomic regions involved in RI frequently harbor anciently diverged haplotypes that predate the reconstructed history of species divergence. The possible origins of these old alleles remain much debated, as they relate to contrasting mechanisms of speciation that are not yet fully understood. In the European sea bass (Dicentrarchus labrax), the genomic regions involved in RI between Atlantic and Mediterranean lineages are enriched for anciently diverged alleles of unknown origin. Here, we used haplotype-resolved whole-genome sequences to test whether divergent haplotypes could have originated from a closely related species, the spotted sea bass (Dicentrarchus punctatus). We found that an ancient admixture event between D. labrax and D. punctatus is responsible for the presence of shared derived alleles that segregate at low frequencies in both lineages of D. labrax. An exception to this was found within regions involved in RI between the two D. labrax lineages. In those regions, archaic tracts originating from D. punctatus locally reached high frequencies or even fixation in Atlantic genomes but were almost absent in the Mediterranean. We showed that the ancient admixture event most likely occurred between D. punctatus and the D. labrax Atlantic lineage, while Atlantic and Mediterranean D. labrax lineages were experiencing allopatric isolation. Our results suggest that local adaptive introgression and/or the resolution of genomic conflicts provoked by ancient admixture have probably contributed to the establishment of RI between the two D. labrax lineages.
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Affiliation(s)
- Maud Duranton
- ISEM Univ Montpellier, CNRS, EPHE, IRD Montpellier France
| | - François Allal
- MARBEC Université de Montpellier, Ifremer-CNRS-IRD-UM Palavas-les-Flots 34250 France
| | - Sophie Valière
- INRA, US 1426, GeT-PlaGe Genotoul Castanet-Tolosan 31326 France
| | - Olivier Bouchez
- INRA, US 1426, GeT-PlaGe Genotoul Castanet-Tolosan 31326 France
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26
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Oldfather MF, Kling MM, Sheth SN, Emery NC, Ackerly DD. Range edges in heterogeneous landscapes: Integrating geographic scale and climate complexity into range dynamics. GLOBAL CHANGE BIOLOGY 2020; 26:1055-1067. [PMID: 31674701 DOI: 10.1111/gcb.14897] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 10/01/2019] [Indexed: 05/04/2023]
Abstract
The impacts of climate change have re-energized interest in understanding the role of climate in setting species geographic range edges. Despite the strong focus on species' distributions in ecology and evolution, defining a species range edge is theoretically and empirically difficult. The challenge of determining a range edge and its relationship to climate is in part driven by the nested nature of geography and the multidimensionality of climate, which together generate complex patterns of both climate and biotic distributions across landscapes. Because range-limiting processes occur in both geographic and climate space, the relationship between these two spaces plays a critical role in setting range limits. With both conceptual and empirical support, we argue that three factors-climate heterogeneity, collinearity among climate variables, and spatial scale-interact to shape the spatial structure of range edges along climate gradients, and we discuss several ways that these factors influence the stability of species range edges with a changing climate. We demonstrate that geographic and climate edges are often not concordant across species ranges. Furthermore, high climate heterogeneity and low climate collinearity across landscapes increase the spectrum of possible relationships between geographic and climatic space, suggesting that geographic range edges and climatic niche limits correspond less frequently than we may expect. More empirical explorations of how the complexity of real landscapes shapes the ecological and evolutionary processes that determine species range edges will advance the development of range limit theory and its applications to biodiversity conservation in the context of changing climate.
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Affiliation(s)
- Meagan F Oldfather
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Matthew M Kling
- Department of Integrative Biology, University of California Berkeley, Berkeley, CA, USA
| | - Seema N Sheth
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, USA
| | - Nancy C Emery
- Department of Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO, USA
| | - David D Ackerly
- Department of Integrative Biology, Department of Environmental Science, Policy, and Management, Jepson Herbarium, University of California Berkeley, Berkeley, CA, USA
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Leitwein M, Duranton M, Rougemont Q, Gagnaire PA, Bernatchez L. Using Haplotype Information for Conservation Genomics. Trends Ecol Evol 2020; 35:245-258. [DOI: 10.1016/j.tree.2019.10.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/18/2019] [Accepted: 10/28/2019] [Indexed: 12/19/2022]
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Li X, Kumar S, McDew-White M, Haile M, Cheeseman IH, Emrich S, Button-Simons K, Nosten F, Kappe SHI, Ferdig MT, Anderson TJC, Vaughan AM. Genetic mapping of fitness determinants across the malaria parasite Plasmodium falciparum life cycle. PLoS Genet 2019; 15:e1008453. [PMID: 31609965 PMCID: PMC6821138 DOI: 10.1371/journal.pgen.1008453] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 10/30/2019] [Accepted: 10/01/2019] [Indexed: 12/14/2022] Open
Abstract
Determining the genetic basis of fitness is central to understanding evolution and transmission of microbial pathogens. In human malaria parasites (Plasmodium falciparum), most experimental work on fitness has focused on asexual blood stage parasites, because this stage can be easily cultured, although the transmission of malaria requires both female Anopheles mosquitoes and vertebrate hosts. We explore a powerful approach to identify the genetic determinants of parasite fitness across both invertebrate and vertebrate life-cycle stages of P. falciparum. This combines experimental genetic crosses using humanized mice, with selective whole genome amplification and pooled sequencing to determine genome-wide allele frequencies and identify genomic regions under selection across multiple lifecycle stages. We applied this approach to genetic crosses between artemisinin resistant (ART-R, kelch13-C580Y) and ART-sensitive (ART-S, kelch13-WT) parasites, recently isolated from Southeast Asian patients. Two striking results emerge: we observed (i) a strong genome-wide skew (>80%) towards alleles from the ART-R parent in the mosquito stage, that dropped to ~50% in the blood stage as selfed ART-R parasites were selected against; and (ii) repeatable allele specific skews in blood stage parasites with particularly strong selection (selection coefficient (s) ≤ 0.18/asexual cycle) against alleles from the ART-R parent at loci on chromosome 12 containing MRP2 and chromosome 14 containing ARPS10. This approach robustly identifies selected loci and has strong potential for identifying parasite genes that interact with the mosquito vector or compensatory loci involved in drug resistance.
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Affiliation(s)
- Xue Li
- Texas Biomedical Research Institute, San Antonio, Texas, United States of America
| | - Sudhir Kumar
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, Washington, United States of America
| | - Marina McDew-White
- Texas Biomedical Research Institute, San Antonio, Texas, United States of America
| | - Meseret Haile
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, Washington, United States of America
| | - Ian H. Cheeseman
- Texas Biomedical Research Institute, San Antonio, Texas, United States of America
| | - Scott Emrich
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
- Electrical Engineering and Computer Science, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Katie Button-Simons
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - François Nosten
- Shoklo Malaria Research Unit, Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Mae Sot, Thailand
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford, United Kingdom
| | - Stefan H. I. Kappe
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, Washington, United States of America
- Department of Global Health, University of Washington, Seattle, Washington, United States of America
| | - Michael T. Ferdig
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Tim J. C. Anderson
- Texas Biomedical Research Institute, San Antonio, Texas, United States of America
- * E-mail: (TJCA); (AMV)
| | - Ashley M. Vaughan
- Center for Global Infectious Disease Research, Seattle Children’s Research Institute, Seattle, Washington, United States of America
- * E-mail: (TJCA); (AMV)
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Koski MH, Layman NC, Prior CJ, Busch JW, Galloway LF. Selfing ability and drift load evolve with range expansion. Evol Lett 2019; 3:500-512. [PMID: 31636942 PMCID: PMC6791181 DOI: 10.1002/evl3.136] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 08/09/2019] [Accepted: 08/11/2019] [Indexed: 12/16/2022] Open
Abstract
Colonization at expanding range edges often involves few founders, reducing effective population size. This process can promote the evolution of self-fertilization, but implicating historical processes as drivers of trait evolution is often difficult and requires an explicit model of biogeographic history. In plants, contemporary limits to outcrossing are often invoked as evolutionary drivers of self-fertilization, but historical expansions may shape mating system diversity, with leading-edge populations evolving elevated selfing ability. In a widespread plant, Campanula americana, we identified a glacial refugium in the southern Appalachian Mountains from spatial patterns of genetic drift among 24 populations. Populations farther from this refugium have smaller effective sizes and fewer rare alleles. They also displayed elevated heterosis in among-population crosses, reflecting the accumulation of deleterious mutations during range expansion. Although populations with elevated heterosis had reduced segregating mutation load, the magnitude of inbreeding depression lacked geographic pattern. The ability to self-fertilize was strongly positively correlated with the distance from the refugium and mutation accumulation-a pattern that contrasts sharply with contemporary mate and pollinator limitation. In this and other species, diversity in sexual systems may reflect the legacy of evolution in small, colonizing populations, with little or no relation to the ecology of modern populations.
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Affiliation(s)
- Matthew H Koski
- Department of Biology University of Virginia Charlottesville Virginia 22902.,Current Address: Department of Biological Sciences Clemson University Clemson SC 29631
| | - Nathan C Layman
- School of Biological Sciences Washington State University Pullman Washington 99164
| | - Carly J Prior
- School of Biological Sciences Washington State University Pullman Washington 99164
| | - Jeremiah W Busch
- School of Biological Sciences Washington State University Pullman Washington 99164
| | - Laura F Galloway
- Department of Biology University of Virginia Charlottesville Virginia 22902
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30
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Brady SP, Bolnick DI, Barrett RDH, Chapman L, Crispo E, Derry AM, Eckert CG, Fraser DJ, Fussmann GF, Gonzalez A, Guichard F, Lamy T, Lane J, McAdam AG, Newman AEM, Paccard A, Robertson B, Rolshausen G, Schulte PM, Simons AM, Vellend M, Hendry A. Understanding Maladaptation by Uniting Ecological and Evolutionary Perspectives. Am Nat 2019; 194:495-515. [PMID: 31490718 DOI: 10.1086/705020] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Evolutionary biologists have long trained their sights on adaptation, focusing on the power of natural selection to produce relative fitness advantages while often ignoring changes in absolute fitness. Ecologists generally have taken a different tack, focusing on changes in abundance and ranges that reflect absolute fitness while often ignoring relative fitness. Uniting these perspectives, we articulate various causes of relative and absolute maladaptation and review numerous examples of their occurrence. This review indicates that maladaptation is reasonably common from both perspectives, yet often in contrasting ways. That is, maladaptation can appear strong from a relative fitness perspective, yet populations can be growing in abundance. Conversely, resident individuals can appear locally adapted (relative to nonresident individuals) yet be declining in abundance. Understanding and interpreting these disconnects between relative and absolute maladaptation, as well as the cases of agreement, is increasingly critical in the face of accelerating human-mediated environmental change. We therefore present a framework for studying maladaptation, focusing in particular on the relationship between absolute and relative fitness, thereby drawing together evolutionary and ecological perspectives. The unification of these ecological and evolutionary perspectives has the potential to bring together previously disjunct research areas while addressing key conceptual issues and specific practical problems.
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31
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Cruzan MB. How to Make a Weed: The Saga of the Slender False Brome Invasion in the North American West and Lessons for the Future. Bioscience 2019. [DOI: 10.1093/biosci/biz051] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Historical herbarium collections and genetic analyses indicate that slender false brome (Brachypodium sylvaticum) was first introduced in test gardens in Oregon in the early 1900 s as part of the USDA’s plant introduction program. A small number of naturalized populations were established, but it was not until several decades later that this alien species became an aggressive invader. The Oregon invasive strains of false brome were generated as a consequence of mating among genetically divergent lineages. The resulting hybrid populations contained high levels of genetic variation that fueled the evolution of specific adaptations to the Pacific Northwest climate and ultimately generated genetically superior lineages. Although the false brome invasion has caused significant ecological and economic harm and is expected to continue spreading across western North America, understanding the circumstances that have promoted its success may provide valuable lessons for the management of native plants under pressure from global climate change.
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Affiliation(s)
- Mitchell B Cruzan
- Department ofBiology at Portland State University, in Portland, Oregon
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32
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Abstract
Factors that limit the geographic distribution of species are broadly important in ecology and evolutionary biology, and understanding distribution limits is imperative for predicting how species will respond to environmental change. Good data indicate that factors such as dispersal limitation, small effective population size, and isolation are sometimes important. But empirical research highlights no single factor that explains the ubiquity of distribution limits. In this article, we outline a guide to tackling distribution limits that integrates established causes, such as dispersal limitation and spatial environmental heterogeneity, with understudied causes, such as mutational load and genetic or developmental integration of traits limiting niche expansion. We highlight how modeling and quantitative genetic and genomic analyses can provide insight into sources of distribution limits. Our practical guide provides a framework for considering the many factors likely to determine species distributions and how the different approaches can be integrated to predict distribution limits using eco-evolutionary modeling. The framework should also help predict distribution limits of invasive species and of species under climate change.
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Oakley CG, Lundemo S, Ågren J, Schemske DW. Heterosis is common and inbreeding depression absent in natural populations of
Arabidopsis thaliana. J Evol Biol 2019; 32:592-603. [DOI: 10.1111/jeb.13441] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 02/23/2019] [Accepted: 03/11/2019] [Indexed: 01/09/2023]
Affiliation(s)
| | - Sverre Lundemo
- Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Uppsala Sweden
| | - Jon Ågren
- Plant Ecology and Evolution Department of Ecology and Genetics Evolutionary Biology Centre Uppsala University Uppsala Sweden
| | - Douglas W. Schemske
- Department of Plant Biology W. K. Kellogg Biological Station Michigan State University East Lansing Michigan
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34
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Harkness A, Brandvain Y, Goldberg EE. The evolutionary response of mating system to heterosis. J Evol Biol 2019; 32:476-490. [DOI: 10.1111/jeb.13430] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 01/28/2019] [Accepted: 02/04/2019] [Indexed: 11/30/2022]
Affiliation(s)
- Alexander Harkness
- Department of Ecology, Evolution, and BehaviorUniversity of Minnesota St. Paul Minnesota
| | - Yaniv Brandvain
- Department of Plant and Microbial BiologyUniversity of Minnesota St. Paul Minnesota
| | - Emma E. Goldberg
- Department of Ecology, Evolution, and BehaviorUniversity of Minnesota St. Paul Minnesota
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Luquet E, Rödin Mörch P, Cortázar‐Chinarro M, Meyer‐Lucht Y, Höglund J, Laurila A. Post‐glacial colonization routes coincide with a life‐history breakpoint along a latitudinal gradient. J Evol Biol 2019; 32:356-368. [DOI: 10.1111/jeb.13419] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 01/23/2019] [Accepted: 01/24/2019] [Indexed: 01/17/2023]
Affiliation(s)
- Emilien Luquet
- Univ LyonUniversité Claude Bernard Lyon 1CNRSENTPEUMR5023 LEHNA Villeurbanne France
| | - Patrik Rödin Mörch
- Animal Ecology/Department of Ecology and GeneticsEvolutionary Biology CentreUppsala University Uppsala Sweden
| | - Maria Cortázar‐Chinarro
- Animal Ecology/Department of Ecology and GeneticsEvolutionary Biology CentreUppsala University Uppsala Sweden
| | - Yvonne Meyer‐Lucht
- Animal Ecology/Department of Ecology and GeneticsEvolutionary Biology CentreUppsala University Uppsala Sweden
| | - Jacob Höglund
- Animal Ecology/Department of Ecology and GeneticsEvolutionary Biology CentreUppsala University Uppsala Sweden
| | - Anssi Laurila
- Animal Ecology/Department of Ecology and GeneticsEvolutionary Biology CentreUppsala University Uppsala Sweden
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36
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Charlesworth B. Mutational load, inbreeding depression and heterosis in subdivided populations. Mol Ecol 2018; 27:4991-5003. [DOI: 10.1111/mec.14933] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 10/05/2018] [Accepted: 10/08/2018] [Indexed: 01/02/2023]
Affiliation(s)
- Brian Charlesworth
- Institute of Evolutionary Biology School of Biological Sciences University of Edinburgh Edinburgh UK
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37
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Kim BY, Huber CD, Lohmueller KE. Deleterious variation shapes the genomic landscape of introgression. PLoS Genet 2018; 14:e1007741. [PMID: 30346959 PMCID: PMC6233928 DOI: 10.1371/journal.pgen.1007741] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 11/13/2018] [Accepted: 10/05/2018] [Indexed: 11/19/2022] Open
Abstract
While it is appreciated that population size changes can impact patterns of deleterious variation in natural populations, less attention has been paid to how gene flow affects and is affected by the dynamics of deleterious variation. Here we use population genetic simulations to examine how gene flow impacts deleterious variation under a variety of demographic scenarios, mating systems, dominance coefficients, and recombination rates. Our results show that admixture between populations can temporarily reduce the genetic load of smaller populations and cause increases in the frequency of introgressed ancestry, especially if deleterious mutations are recessive. Additionally, when fitness effects of new mutations are recessive, between-population differences in the sites at which deleterious variants exist creates heterosis in hybrid individuals. Together, these factors lead to an increase in introgressed ancestry, particularly when recombination rates are low. Under certain scenarios, introgressed ancestry can increase from an initial frequency of 5% to 30–75% and fix at many loci, even in the absence of beneficial mutations. Further, deleterious variation and admixture can generate correlations between the frequency of introgressed ancestry and recombination rate or exon density, even in the absence of other types of selection. The direction of these correlations is determined by the specific demography and whether mutations are additive or recessive. Therefore, it is essential that null models of admixture include both demography and deleterious variation before invoking other mechanisms to explain unusual patterns of genetic variation. Individuals from distinct populations sometimes will produce fertile offspring and will exchange genetic material in a process called hybridization. Genomes of hybrid individuals often show non-random patterns of hybrid ancestry across the genome, where some regions have a high frequency of ancestry from the second population and other regions have less. Typically, this pattern has been attributed to adaptive introgression, where beneficial genetic variants are passed from one population to the other, or to genomic incompatibilities between these distinct species. However, other mechanisms could lead to these heterogeneous patterns of ancestry in hybrids. Here we use simulations to investigate whether deleterious mutations affect the patterns of introgressed ancestry across genomes. We show that when ancestry from a larger population is added to a smaller population, the ancestry from the larger population dramatically increases in frequency because it carries fewer deleterious mutations. This occurs even in the absence of beneficial mutations in either population. Additionally, we show that differences in sex chromosome evolution relative to autosomes, or differences in mating system, can affect patterns of introgression in similar ways. Our study argues that deleterious mutations should be included in population genetic models used to identify unusual regions of the genome that appear to be under selection in hybrids.
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Affiliation(s)
- Bernard Y. Kim
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, United States of America
| | - Christian D. Huber
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, United States of America
| | - Kirk E. Lohmueller
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, United States of America
- Interdepartmental Program in Bioinformatics, University of California, Los Angeles, California, United States of America
- Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- * E-mail:
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39
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Conte GL, Hodgins KA, Yeaman S, Degner JC, Aitken SN, Rieseberg LH, Whitlock MC. Bioinformatically predicted deleterious mutations reveal complementation in the interior spruce hybrid complex. BMC Genomics 2017; 18:970. [PMID: 29246191 PMCID: PMC5731209 DOI: 10.1186/s12864-017-4344-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Accepted: 11/21/2017] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Mutation load is expected to be reduced in hybrids via complementation of deleterious alleles. While local adaptation of hybrids confounds phenotypic tests for reduced mutation load, it may be possible to assess variation in load by analyzing the distribution of putatively deleterious alleles. Here, we use this approach in the interior spruce (Picea glauca x P. engelmannii) hybrid complex, a group likely to suffer from high mutation load and in which hybrids exhibit local adaptation to intermediate conditions. We used PROVEAN to bioinformatically predict whether non-synonymous alleles are deleterious, based on conservation of the position and abnormality of the amino acid change. RESULTS As expected, we found that predicted deleterious alleles were at lower average allele frequencies than alleles not predicted to be deleterious. We were unable to detect a phenotypic effect on juvenile growth rate of the many rare alleles predicted to be deleterious. Both the proportion of alleles predicted to be deleterious and the proportion of loci homozygous for predicted deleterious alleles were higher in P. engelmannii (Engelmann spruce) than in P. glauca (white spruce), due to higher diversity and frequencies of rare alleles in Engelmann. Relative to parental species, the proportion of alleles predicted to be deleterious was intermediate in hybrids, and the proportion of loci homozygous for predicted deleterious alleles was lowest. CONCLUSION Given that most deleterious alleles are recessive, this suggests that mutation load is reduced in hybrids due to complementation of deleterious alleles. This effect may enhance the fitness of hybrids.
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Affiliation(s)
- Gina L Conte
- Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada. .,Department of Botany, University of British Columbia, 3200-6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada.
| | - Kathryn A Hodgins
- Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.,Present Address: School of Biological Sciences, Monash University, Clayton Campus, Melbourne, Victoria, 3800, Australia
| | - Sam Yeaman
- Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.,Present Address: Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, AB, T2N 1N4, Canada
| | - Jon C Degner
- Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| | - Sally N Aitken
- Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| | - Loren H Rieseberg
- Department of Botany, University of British Columbia, 3200-6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada
| | - Michael C Whitlock
- Department of Zoology, University of British Columbia, 4200-6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada
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Moyers BT, Morrell PL, McKay JK. Genetic Costs of Domestication and Improvement. J Hered 2017; 109:103-116. [DOI: 10.1093/jhered/esx069] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 08/02/2017] [Indexed: 12/12/2022] Open
Affiliation(s)
- Brook T Moyers
- Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO
| | - Peter L Morrell
- Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN (Morrell)
| | - John K McKay
- Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO
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Genetic differentiation of the Schizothorax species complex (Cyprinidae) in the Nujiang River (upper Salween). Sci Rep 2017; 7:5944. [PMID: 28729545 PMCID: PMC5519740 DOI: 10.1038/s41598-017-06172-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 06/07/2017] [Indexed: 11/08/2022] Open
Abstract
Phenotypically diverse species from recently evolved groups always share allele/haplotype due to insufficient differentiation in the early process. In this study, we performed population genetics analyses using sequences from the mitochondrial cytochrome b gene, and two nuclear genes to investigate the genetic differentiation of the closely related Schizothorax species complex, comprising a group of alpine fish living in the Nujiang River. The results from both mtDNA and nDNA markers revealed relatively low but pronounced genetic differentiation among the three Schizothorax species, i.e., Schizothorax gongshanensis, S. lissolabiatus, and S. nukiangensis. However, haplotype sharing was frequently occurred among the three species. Divergence time estimation suggested the last glaciation on the Tibetan Plateau (0.075–0.01 Ma) might drive the divergence of the species complex. Gene flow might contribute to the haplotype sharing between S. gongshanensis and S. lissolabiatus, and between S. gongshanensis and S. nukiangensis, whereas retention of ancestral polymorphisms seemed to be a better explanation of the haplotype sharing between S. lissolabiatus and S. nukiangensis. In addition, S. lissolabiatus populations should obtain more protection in the future because of their low genetic diversity and habitat fragmentation. In summary, our study assesses genetic differentiation among the three closely related Schizothorax species and explores the possible driving forces for their differentiation.
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Liu X, Liang H, Li Z, Liang Y, Lu C, Li C, Chang Y, Zou G, Hu G. Performances of the hybrid between CyCa nucleocytplasmic hybrid fish and scattered mirror carp in different culture environments. Sci Rep 2017; 7:46329. [PMID: 28402331 PMCID: PMC5389345 DOI: 10.1038/srep46329] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 03/15/2017] [Indexed: 11/09/2022] Open
Abstract
To improve the performance of growth traits and survival in common carp, CyCa nucleocytoplasmic hybrid fish (C) was used as parental fish for hybridization with Russian scattered mirror carp (R). Performances in morphological characters, growth traits and survival rate were compared among the purebreds (CC & RR) and crossbreds (RC & CR) at different time period in solitary and communal rearing system, respectively. The results demonstrated that both RC and CR crossbreds inherited the grey skin color type from the mirror carp, and got the full-scale pattern from the CyCa nucleocytoplasmic hybrid fish, which suggested that the grey color dominated to red color and full-scale dominated to scattered scale. With respect to yield, the RC crossbreds perform quite great compared to the RR and CC purebreds because they have quite high growth and survival rate. In contrast to RC crossbreds, the CR crossbreds performed poorly in growth traits, together with that crosses where scattered mirror carp was used as mother (RC and RR) achieved the greatest performance for all growth traits, suggested that the maternal influence also displayed an important role in growth traits. These results indicated that the RC crossbreds will be a potential carp variety for commercial production.
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Affiliation(s)
- Xiangjiang Liu
- College of Fisheries, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Huazhong Agricultural University, Wuhan, 430070, China
| | - Hongwei Liang
- Yangtze River Fisheries Research Institute, The Chinese Academy of Fisheries Sciences, Wuhan, 430223, China
| | - Zhong Li
- Yangtze River Fisheries Research Institute, The Chinese Academy of Fisheries Sciences, Wuhan, 430223, China
| | - Yongjun Liang
- Beijing Key Laboratory of fishery Biotechnology, Beijing Fisheries Research Institute, Beijing, 100068, China
| | - Cuiyun Lu
- Key Laboratory of Freshwater Aquatic Biotechnology and Breeding, Ministry of Agriculture, Heilongjiang Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin 150070, China
| | - Chitao Li
- Key Laboratory of Freshwater Aquatic Biotechnology and Breeding, Ministry of Agriculture, Heilongjiang Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin 150070, China
| | - Yumei Chang
- Key Laboratory of Freshwater Aquatic Biotechnology and Breeding, Ministry of Agriculture, Heilongjiang Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin 150070, China
| | - Guiwei Zou
- Yangtze River Fisheries Research Institute, The Chinese Academy of Fisheries Sciences, Wuhan, 430223, China
| | - Guangfu Hu
- College of Fisheries, Key Laboratory of Freshwater Animal Breeding, Ministry of Agriculture, Freshwater Aquaculture Collaborative Innovation Center of Hubei Province, Huazhong Agricultural University, Wuhan, 430070, China
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43
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Spigler RB, Theodorou K, Chang S. Inbreeding depression and drift load in small populations at demographic disequilibrium. Evolution 2016; 71:81-94. [DOI: 10.1111/evo.13103] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 10/11/2016] [Accepted: 10/13/2016] [Indexed: 11/27/2022]
Affiliation(s)
- Rachel B. Spigler
- Department of Biology Temple University 1900 N. 12th Street Philadelphia Pennsylvania 19122
| | - Konstantinos Theodorou
- Biodiversity Conservation Laboratory, Department of Environment, University of the Aegean University Hill 81100 Mytilene Greece
| | - Shu‐Mei Chang
- Department of Plant Biology University of Georgia 2502 Miller Plant Sciences Athens Georgia 30602–7271
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44
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Melen MK, Herman JA, Lucas J, O'Malley RE, Parker IM, Thom AM, Whittall JB. Reproductive success through high pollinator visitation rates despite self incompatibility in an endangered wallflower. AMERICAN JOURNAL OF BOTANY 2016; 103:1979-1989. [PMID: 27864264 DOI: 10.3732/ajb.1600193] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 10/25/2016] [Indexed: 06/06/2023]
Abstract
PREMISE OF THE STUDY Self incompatibility (SI) in rare plants presents a unique challenge-SI protects plants from inbreeding depression, but requires a sufficient number of mates and xenogamous pollination. Does SI persist in an endangered polyploid? Is pollinator visitation sufficient to ensure reproductive success? Is there evidence of inbreeding/outbreeding depression? We characterized the mating system, primary pollinators, pollen limitation, and inbreeding/outbreeding depression in Erysimum teretifolium to guide conservation efforts. METHODS We compared seed production following self pollination and within- and between-population crosses. Pollen tubes were visualized after self pollinations and between-population pollinations. Pollen limitation was tested in the field. Pollinator observations were quantified using digital video. Inbreeding/outbreeding depression was assessed in progeny from self and outcross pollinations at early and later developmental stages. KEY RESULTS Self-pollination reduced seed set by 6.5× and quadrupled reproductive failure compared with outcross pollination. Pollen tubes of some self pollinations were arrested at the stigmatic surface. Seed-set data indicated strong SI, and fruit-set data suggested partial SI. Pollinator diversity and visitation rates were high, and there was no evidence of pollen limitation. Inbreeding depression (δ) was weak for early developmental stages and strong for later developmental stages, with no evidence of outbreeding depression. CONCLUSIONS The rare hexaploid E. teretifolium is largely self incompatible and suffers from late-acting inbreeding depression. Reproductive success in natural populations was accomplished through high pollinator visitation rates consistent with a lack of pollen limitation. Future reproductive health for this species will require large population sizes with sufficient mates and a robust pollinator community.
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Affiliation(s)
- Miranda K Melen
- Department of Environmental Studies, San Jose State University, One Washington Square, San Jose, California 95192 USA
| | - Julie A Herman
- Department of Biology, Santa Clara University, 500 El Camino Real, Santa Clara, California 95053 USA
| | - Jessica Lucas
- Southern Illinois University, 1125 Lincoln Drive, Carbondale, Illinois 62902 USA
| | - Rachel E O'Malley
- Department of Environmental Studies, San Jose State University, One Washington Square, San Jose, California 95192 USA
| | - Ingrid M Parker
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, 1156 High Street, Santa Cruz, California 95064 USA
| | - Aaron M Thom
- Department of Biology, Santa Clara University, 500 El Camino Real, Santa Clara, California 95053 USA
| | - Justen B Whittall
- Department of Biology, Santa Clara University, 500 El Camino Real, Santa Clara, California 95053 USA
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45
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Rettelbach A, Servedio MR, Hermisson J. Speciation in peripheral populations: effects of drift load and mating systems. J Evol Biol 2016; 29:1073-90. [PMID: 26929184 DOI: 10.1111/jeb.12849] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 01/23/2016] [Accepted: 02/13/2016] [Indexed: 12/25/2022]
Abstract
Speciation in peripheral populations has long been considered one of the most plausible scenarios for speciation with gene flow. In this study, however we identify two additional problems of peripatric speciation, as compared to the parapatric case, that may impede the completion of the speciation process for most parameter regions. First, with (predominantly) unidirectional gene flow, there is no selection pressure to evolve assortative mating on the continent. We discuss the implications of this for different mating schemes. Second, genetic load can build up in small populations. This can lead to extinction of the peripheral species, or generate selection pressure for lower assortative mating to avoid inbreeding. In this case, either a stable equilibrium with intermediate assortment evolves or there is cycling between phases of hybridization and phases of complete isolation.
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Affiliation(s)
- A Rettelbach
- Department of Mathematics, University of Vienna, Vienna, Austria
| | - M R Servedio
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | - J Hermisson
- Department of Mathematics, University of Vienna, Vienna, Austria.,Max-Perutz-Laboratories, University of Vienna, Vienna, Austria
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46
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Lohr JN, Haag CR. Genetic load, inbreeding depression, and hybrid vigor covary with population size: An empirical evaluation of theoretical predictions. Evolution 2015; 69:3109-22. [PMID: 26497949 DOI: 10.1111/evo.12802] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 10/07/2015] [Accepted: 10/14/2015] [Indexed: 11/26/2022]
Abstract
Reduced population size is thought to have strong consequences for evolutionary processes as it enhances the strength of genetic drift. In its interaction with selection, this is predicted to increase the genetic load, reduce inbreeding depression, and increase hybrid vigor, and in turn affect phenotypic evolution. Several of these predictions have been tested, but comprehensive studies controlling for confounding factors are scarce. Here, we show that populations of Daphnia magna, which vary strongly in genetic diversity, also differ in genetic load, inbreeding depression, and hybrid vigor in a way that strongly supports theoretical predictions. Inbreeding depression is positively correlated with genetic diversity (a proxy for Ne ), and genetic load and hybrid vigor are negatively correlated with genetic diversity. These patterns remain significant after accounting for potential confounding factors and indicate that, in small populations, a large proportion of the segregation load is converted into fixed load. Overall, the results suggest that the nature of genetic variation for fitness-related traits differs strongly between large and small populations. This has large consequences for evolutionary processes in natural populations, such as selection on dispersal, breeding systems, ageing, and local adaptation.
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Affiliation(s)
- Jennifer N Lohr
- Department of Biology, Ecology and Evolution, University of Fribourg, 1700, Fribourg, Switzerland. .,Zoological Institute and Zoological Museum, Biocenter Grindel, Hamburg University, Hamburg, Germany. .,Tvärminne Zoological Station, FIN-10900, Hanko, Finland.
| | - Christoph R Haag
- Department of Biology, Ecology and Evolution, University of Fribourg, 1700, Fribourg, Switzerland.,Zoological Institute and Zoological Museum, Biocenter Grindel, Hamburg University, Hamburg, Germany.,Centre d'Ecologie Fonctionnelle et Evolutive - UMR 5175, 34293, Montpellier Cedex 5, France
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47
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Oakley CG, Spoelhof JP, Schemske DW. Increased heterosis in selfing populations of a perennial forb. AOB PLANTS 2015; 7:plv122. [PMID: 26507567 PMCID: PMC4671326 DOI: 10.1093/aobpla/plv122] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 10/09/2015] [Indexed: 06/05/2023]
Abstract
Quantifying the importance of random genetic drift in natural populations is central to understanding the potential limits to natural selection. One approach is to estimate the magnitude of heterosis, the increased fitness of progeny derived from crosses between populations relative to crosses within populations caused by the heterozygous masking of deleterious recessive or nearly recessive alleles that have been fixed by drift within populations. Self-fertilization is expected to reduce the effective population size by half relative to outcrossing, and population bottlenecks may be common during the transition to selfing. Therefore, chance fixation of deleterious alleles due to drift in selfing populations should increase heterosis between populations. Increased homozygosity due to fixation or loss of alleles should also decrease inbreeding depression within populations. Most populations of the perennial herb Arabidopsis lyrata ssp. lyrata are self-incompatible (SI), but several have evolved self-compatibility and are highly selfing. We quantified heterosis and inbreeding depression in two predominantly self-compatible (SC) and seven SI populations in a field common garden experiment within the species' native range and examined the correlation between these metrics to gauge the similarity in their genetic basis. We measured proportion germination in the lab, and survival and fecundity (flower and seed production) for 2 years in the field, and calculated estimates of cumulative fitness. We found 7.2-fold greater heterosis in SC compared with SI populations, despite substantial heterosis in SI populations (56 %). Inbreeding depression was >61 %, and not significantly different between SC and SI populations. There was no correlation between population estimates of heterosis and inbreeding depression, suggesting that they have somewhat different genetic bases. Combined with other sources of information, our results suggest a history of bottlenecks in all of these populations. The bottlenecks in SC populations may have been severe, but their strong inbreeding depression remains enigmatic.
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Affiliation(s)
- Christopher G Oakley
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824-1312, USA
| | - Jonathan P Spoelhof
- Department of Plant Biology, Michigan State University, East Lansing, MI 48824-1312, USA
| | - Douglas W Schemske
- Department of Plant Biology and W. K. Kellogg Biological Station, Michigan State University, East Lansing, MI 48824, USA
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48
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Waller DM. Genetic rescue: a safe or risky bet? Mol Ecol 2015; 24:2595-7. [PMID: 26013990 DOI: 10.1111/mec.13220] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 04/24/2015] [Indexed: 12/22/2022]
Abstract
Small and isolated populations face threats from genetic drift and inbreeding. To rescue populations from these threats, conservation biologists can augment gene flow into small populations to increase variation and reduce inbreeding depression. Spectacular success stories include greater prairie chickens in Illinois (Westermeier et al. ), adders in Sweden (Madsen et al. ) and panthers in Florida (Johnson et al. ). However, we also know that performing such crosses risks introducing genes that may be poorly adapted to local conditions or genetic backgrounds. A classic example of such 'outbreeding depression' occurred when different subspecies of ibex from Turkey and the Sinai were introduced to assist recovery of an ibex population in Czechoslovakia (Templeton ). Despite being fertile, the hybrids birthed calves too early, causing the whole population to disappear. In the face of uncertainty, conservation biologists have tended to respect genetic identity, shying away from routinely crossing populations. In this issue of Molecular Ecology, Frankham () compiles empirical data from experimental studies to assess the costs and benefits of between-population crosses (Fig. ). Crosses screened to exclude those involving highly divergent populations or distinct habitats show large heterosis with few apparent risks of outbreeding depression. This leads Frankham to advocate for using assisted gene flow more widely. But do the studies analysed in this meta-analysis adequately test for latent outcrossing depression?
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Affiliation(s)
- Donald M Waller
- Department of Botany, University of Wisconsin - Madison, 430 Lincoln Drive, Madison, WI, 53706-1381, USA
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49
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Van Vianen JCCM, Houliston GJ, Fletcher JD, Heenan PB, Chapman HM. Consequences of interspecific hybridization and virus infection on the growth and fecundity of three threatened coastal Lepidium(Brassicaceae) species from New Zealand. AUSTRAL ECOL 2015. [DOI: 10.1111/aec.12234] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Josh C. C. M. Van Vianen
- School of Biological Sciences; University of Canterbury; Private Bag 4800 Christchurch 8149 New Zealand
| | | | - John D. Fletcher
- The New Zealand Institute for Plant and Food Research Ltd; Christchurch New Zealand
| | | | - Hazel M. Chapman
- School of Biological Sciences; University of Canterbury; Private Bag 4800 Christchurch 8149 New Zealand
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50
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Fields PD, Reisser C, Dukić M, Haag CR, Ebert D. Genes mirror geography inDaphnia magna. Mol Ecol 2015; 24:4521-36. [DOI: 10.1111/mec.13324] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2015] [Revised: 07/13/2015] [Accepted: 07/14/2015] [Indexed: 02/06/2023]
Affiliation(s)
- Peter D. Fields
- Zoological Institute; University of Basel; Vesalgasse 1 Basel CH-4051 Switzerland
| | - Céline Reisser
- Centre d'Ecologie Fonctionnelle et Evolutive - UMR 5175; campus CNRS 1919 route de Mende 34293 Montpellier Cedex 5 France
- Department of Biology; Ecology and Evolution; University of Fribourg; Chemin du Muśee 10 1700 Fribourg Switzerland
| | - Marinela Dukić
- Zoological Institute; University of Basel; Vesalgasse 1 Basel CH-4051 Switzerland
| | - Christoph R. Haag
- Centre d'Ecologie Fonctionnelle et Evolutive - UMR 5175; campus CNRS 1919 route de Mende 34293 Montpellier Cedex 5 France
- Department of Biology; Ecology and Evolution; University of Fribourg; Chemin du Muśee 10 1700 Fribourg Switzerland
| | - Dieter Ebert
- Zoological Institute; University of Basel; Vesalgasse 1 Basel CH-4051 Switzerland
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