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Adhikari B, Caruso CM, Case AL. Beyond balancing selection: frequent mitochondrial recombination contributes to high-female frequencies in gynodioecious Lobelia siphilitica (Campanulaceae). THE NEW PHYTOLOGIST 2019; 224:1381-1393. [PMID: 31442304 DOI: 10.1111/nph.16136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2019] [Accepted: 08/13/2019] [Indexed: 06/10/2023]
Abstract
Gynodioecy is a sexual system in which females and hermaphrodites co-occur. In most gynodioecious angiosperms, sex is determined by an interaction between mitochondrial male-sterility genes (CMS) that arise via recombination and nuclear restorer alleles that evolve to suppress them. In theory, gynodioecy occurs when multiple CMS types are maintained at equilibrium frequencies by balancing selection. However, some gynodioecious populations contain very high frequencies of females. High female frequencies are not expected under balancing selection, but could be explained by the repeated introduction of novel CMS types. To test for balancing selection and/or the repeated introduction of novel CMS, we characterised cytoplasmic haplotypes from 61 populations of Lobelia siphilitica that vary widely in female frequency. We confirmed that mitotype diversity and female frequency were positively correlated across populations, consistent with balancing selection. However, while low-female populations hosted mostly common mitotypes, high-female populations and female plants hosted mostly rare, recombinant mitotypes likely to carry novel CMS types. Our results suggest that balancing selection maintains established CMS types across this species, but extreme female frequencies result from frequent invasion by novel CMS types. We conclude that balancing selection alone cannot account for extreme population sex-ratio variation within a gynodioecious species.
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Affiliation(s)
- Binaya Adhikari
- Department of Biological Sciences, Kent State University, Kent, OH, 44240, USA
- Department of Biological and Environmental Sciences, Longwood University, Farmville, VA, 23909, USA
| | - Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada
| | - Andrea L Case
- Department of Biological Sciences, Kent State University, Kent, OH, 44240, USA
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Mollion M, Ehlers BK, Figuet E, Santoni S, Lenormand T, Maurice S, Galtier N, Bataillon T. Patterns of Genome-Wide Nucleotide Diversity in the Gynodioecious Plant Thymus vulgaris Are Compatible with Recent Sweeps of Cytoplasmic Genes. Genome Biol Evol 2018; 10:239-248. [PMID: 29272394 PMCID: PMC5815141 DOI: 10.1093/gbe/evx272] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/19/2017] [Indexed: 12/14/2022] Open
Abstract
Gynodioecy is a sexual dimorphism where females coexist with hermaphrodite individuals. In most cases, this dimorphism involves the interaction of cytoplasmic male sterility (CMS) genes and nuclear restorer genes. Two scenarios can account for how these interactions maintain gynodioecy. Either CMS genes recurrently enter populations at low frequency via mutation or migration and go to fixation unimpeded (successive sweeps), or CMS genes maintain polymorphism over evolutionary time through interactions with a nuclear restorer allele (balanced polymorphism). To distinguish between these scenarios, we used transcriptome sequencing in gynodioecious Thymus vulgaris and surveyed genome-wide diversity in 18 naturally occurring individuals sampled from populations at a local geographic scale. We contrast the amount and patterns of nucleotide diversity in the nuclear and cytoplasmic genome, and find ample diversity at the nuclear level (π = 0.019 at synonymous sites) but reduced genetic diversity and an excess of rare polymorphisms in the cytoplasmic genome relative to the nuclear genome. Our finding is incompatible with the maintenance of gynodioecy via scenarios invoking long-term balancing selection, and instead suggests the recent fixation of CMS lineages in the populations studied.
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Affiliation(s)
- Maeva Mollion
- Bioinformatics Research Center, Aarhus University, C.F. Møllers Alle 8, Building 1110, 8000 Aarhus C, Denmark
| | - Bodil K Ehlers
- Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark
| | - Emeric Figuet
- Institut des Sciences de l'Evolution, UMR5554 - Université de Montpellier - CNRS - IRD - EPHE, Place E. Bataillon - CC64, 34095 Montpellier, France
| | - Sylvain Santoni
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE), CNRS, 1919, route de Mende 34293 Montpellier, France
| | - Thomas Lenormand
- Centre d'Ecologie Fonctionnelle et Evolutive, CNRS, 1919, route de Mende 34293 Montpellier, France
| | - Sandrine Maurice
- Institut des Sciences de l'Evolution, UMR5554 - Université de Montpellier - CNRS - IRD - EPHE, Place E. Bataillon - CC64, 34095 Montpellier, France
| | - Nicolas Galtier
- Institut des Sciences de l'Evolution, UMR5554 - Université de Montpellier - CNRS - IRD - EPHE, Place E. Bataillon - CC64, 34095 Montpellier, France
| | - Thomas Bataillon
- Bioinformatics Research Center, Aarhus University, C.F. Møllers Alle 8, Building 1110, 8000 Aarhus C, Denmark
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Heller KG, Hemp C. Extremely divergent song types in the genus Aerotegmina Hemp (Orthoptera: Tettigoniidae: Hexacentrinae) and the description of a new species from the Eastern Arc Mountains of Tanzania (East Africa). BIOACOUSTICS 2018. [DOI: 10.1080/09524622.2018.1443284] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Affiliation(s)
| | - Claudia Hemp
- Biodiversity and Climate Research Centre (BiK-F), Frankfurt (Main), Germany
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Dornier A, Dufay M. HOW SELFING, INBREEDING DEPRESSION, AND POLLEN LIMITATION IMPACT NUCLEAR-CYTOPLASMIC GYNODIOECY: A MODEL. Evolution 2013; 67:2674-87. [DOI: 10.1111/evo.12142] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 04/16/2013] [Indexed: 11/26/2022]
Affiliation(s)
- Antoine Dornier
- Laboratoire de Génétique et Evolution des Populations Végétales; UMR-CNRS 8198, Université des Sciences et Technologies de Lille - Lille 1; France
| | - Mathilde Dufay
- Laboratoire de Génétique et Evolution des Populations Végétales; UMR-CNRS 8198, Université des Sciences et Technologies de Lille - Lille 1; France
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Caruso CM, Case AL, Bailey MF. The evolutionary ecology of cytonuclear interactions in angiosperms. TRENDS IN PLANT SCIENCE 2012; 17:638-643. [PMID: 22784826 DOI: 10.1016/j.tplants.2012.06.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 06/08/2012] [Accepted: 06/13/2012] [Indexed: 06/01/2023]
Abstract
Interactions between cytoplasmic and nuclear genomes have significant evolutionary consequences. In angiosperms, the most common cytonuclear interaction is between mitochondrial genes that disrupt pollen production (cytoplasmic male sterility, CMS) and nuclear genes that restore it (nuclear male fertility restorers, Rf). The outcome of CMS/Rf interactions can depend on whether Rf alleles have negative pleiotropic effects on fitness. Although these fitness costs are often considered to be independent of the ecological context, we argue that the effects of Rf alleles on fitness should be context dependent. Thus, measuring the cost of restoration across a range of environments could help explain geographic and phylogenetic variation in the distribution of Rf alleles and the outcome of CMS/Rf interactions.
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Affiliation(s)
- Christina M Caruso
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
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Caruso CM, Case AL. TESTING MODELS OF SEX RATIO EVOLUTION IN A GYNODIOECIOUS PLANT: FEMALE FREQUENCY COVARIES WITH THE COST OF MALE FERTILITY RESTORATION. Evolution 2012; 67:561-6. [DOI: 10.1111/j.1558-5646.2012.01798.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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De Cauwer I, Arnaud JF, Klein EK, Dufay M. Disentangling the causes of heterogeneity in male fecundity in gynodioecious Beta vulgaris ssp. maritima. THE NEW PHYTOLOGIST 2012; 195:676-687. [PMID: 22691102 DOI: 10.1111/j.1469-8137.2012.04191.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Variation among individuals in reproductive success is advocated as a major process driving evolution of sexual polymorphisms in plants, such as gynodioecy where females and hermaphrodites coexist. In gynodioecious Beta vulgaris ssp. maritima, sex determination involves cytoplasmic male sterility (CMS) genes and nuclear restorers of male fertility. Both restored CMS and non-CMS hermaphrodites co-occur. Genotype-specific differences in male fitness are theoretically expected to explain the maintenance of cytonuclear polymorphism. Using genotypic information on seedlings and flowering plants within two metapopulations, we investigated whether male fecundity was influenced by ecological, phenotypic and genetic factors, while taking into account the shape and scale of pollen dispersal. Along with spatially restricted pollen flow, we showed that male fecundity was affected by flowering synchrony, investment in reproduction, pollen production and cytoplasmic identity of potential fathers. Siring success of non-CMS hermaphrodites was higher than that of restored CMS hermaphrodites. However, the magnitude of the difference in fecundity depended on the likelihood of carrying restorer alleles for non-CMS hermaphrodites. Our results suggest the occurrence of a cost of silent restorers, a condition supported by scarce empirical evidence, but theoretically required to maintain a stable sexual polymorphism in gynodioecious species.
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Affiliation(s)
- I De Cauwer
- Laboratoire de Génétique et Évolution des Populations Végétales, UMR CNRS 8198, Bâtiment SN2, Université des Sciences et Technologies de Lille - Lille 1, F-59655 Villeneuve d'Ascq Cedex, France
- Present address: Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
| | - J-F Arnaud
- Laboratoire de Génétique et Évolution des Populations Végétales, UMR CNRS 8198, Bâtiment SN2, Université des Sciences et Technologies de Lille - Lille 1, F-59655 Villeneuve d'Ascq Cedex, France
| | - E K Klein
- INRA, UR 546, Biostatistique et Processus Spatiaux, Domaine St Paul, Site Agroparc, F-84914 Avignon Cedex 9, France
| | - M Dufay
- Laboratoire de Génétique et Évolution des Populations Végétales, UMR CNRS 8198, Bâtiment SN2, Université des Sciences et Technologies de Lille - Lille 1, F-59655 Villeneuve d'Ascq Cedex, France
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Garraud C, Brachi B, Dufay M, Touzet P, Shykoff JA. Genetic determination of male sterility in gynodioecious Silene nutans. Heredity (Edinb) 2011; 106:757-64. [PMID: 20808324 PMCID: PMC3186230 DOI: 10.1038/hdy.2010.116] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Revised: 07/30/2010] [Accepted: 07/30/2010] [Indexed: 11/08/2022] Open
Abstract
Gynodioecy, the coexistence of female and hermaphrodite plants within a species, is often under nuclear-cytoplasmic sex determination, involving cytoplasmic male sterility (CMS) genes and nuclear restorers. A good knowledge of CMS and restorer polymorphism is essential for understanding the evolution and maintenance of gynodioecy, but reciprocal crossing studies remain scarce. Although mitochondrial diversity has been studied in a few gynodioecious species, the relationship between mitotype diversity and CMS status is poorly known. From a French sample of Silene nutans, a gynodioecious species whose sex determination remains unknown, we chose the four most divergent mitotypes that we had sampled at the cytochrome b gene and tested by reciprocal crosses whether they carry distinct CMS genes. We show that gynodioecy in S. nutans is under nuclear-cytoplasmic control, with at least two different CMSs and up to four restorers with epistatic interactions. Female occurrence and frequency were highly dependent on the mitotype, suggesting that the level of restoration varies greatly among CMSs. Two of the mitotypes, which have broad geographic distributions, represent different CMSs and are very unequally restored. We discuss the dynamics of gynodioecy at the large-scale meta-population level.
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Affiliation(s)
- C Garraud
- Laboratoire Ecologie, Systématique et Evolution, UMR 8079 Univ Paris-Sud, Orsay, France.
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Case AL, Caruso CM. A novel approach to estimating the cost of male fertility restoration in gynodioecious plants. THE NEW PHYTOLOGIST 2010; 186:549-557. [PMID: 20180910 DOI: 10.1111/j.1469-8137.2010.03199.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
*In many gynodioecious plants, sex is determined by cytoplasmic male sterility genes (CMS) and nuclear male fertility restorers (Rf). Models predict that the costs of restoration are important determinants of population sex ratios. However, current approaches to the estimation of these costs require prior identification of CMS genotypes, information that is available for few species. *We tested a novel approach to estimating the cost of restoration in natural populations without determining CMS or Rf genotypes. We used estimates of pollen viability and offspring sex ratios from open- and hand-pollinated families of Lobelia siphilitica to test whether the cost of restoration, expressed as low pollen viability, is higher in populations with more females. *Among populations with CMS, we found that variation in pollen viability was higher in small populations with more females, as expected if the proportion of females within populations increases with the maximum cost of restoration. In controlled crosses, families with low pollen viability also produced fewer females, suggesting that variation in viability is primarily determined by the number and frequency of Rf alleles carried. *This approach to estimating the cost of restoration can be applied to other cytonuclear gynodioecious species, offering new opportunities for testing gynodioecy models in the wild.
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Affiliation(s)
- Andrea L Case
- Department of Biological Sciences, Kent State University, Kent, OH, USA.
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McCauley DE, Bailey MF. Recent advances in the study of gynodioecy: the interface of theory and empiricism. ANNALS OF BOTANY 2009; 104:611-20. [PMID: 19515690 PMCID: PMC2729626 DOI: 10.1093/aob/mcp141] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 03/25/2009] [Accepted: 04/29/2009] [Indexed: 05/08/2023]
Abstract
BACKGROUND In this review we report on recent literature concerned with studies of gynodioecy, or the co-occurrence of female and hermaphrodite individuals in natural plant populations. Rather than review this literature in its entirety, our focus is on the interplay between theoretical and empirical approaches to the study of gynodioecy. SCOPE Five areas of active inquiry are considered. These are the cost of restoration, the influence of population structure on spatial sex-ratio variation, the influence of inbreeding on sex expression, the signature of cyto-nuclear coevolution on the mitochondrial genome, and the consequences of mitochondrial paternal leakage. CONCLUSIONS Recent advances in the study of gynodioecy have been made by considering both the ecology of female:hermaphrodite fitness differences and the genetics of sex expression. Indeed theory has guided empiricism and empiricism has guided theory. Future advances will require that some of the methods currently available only for model organisms be applied to a wider range of species.
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Affiliation(s)
- David E McCauley
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA.
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