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Christina M Caruso - One of the best experts on this subject based on the ideXlab platform.
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Physiological effects of temperature do not explain prevalence of females in populations of gynodioecious Lobelia siphilitica growing in warmer climates.
American journal of botany, 2017Co-Authors: M.f. Bailey, Andrea L Case, Christina M CarusoAbstract:Premise of the study Gynodioecy is a sexual polymorphism whereby female and hermaphroditic plants co-occur within populations. In many gynodioecious species, stressful abiotic environments are associated with higher frequencies of females. This association suggests that abiotic stress affects the relative fitness of females and hermaphrodites and, thus, the maintenance of Gynodioecy. Methods To test whether abiotic stress affects the fitness of females and hermaphrodites, we grew open-pollinated Lobelia siphilitica families in temperature regimes characteristic of the southern portion of the species' range (where females are common) and the northern portion of the range (where females are rare). We measured physiological and phenological traits that are indicative of heat stress, and fitness components of females and hermaphrodites that could affect the maintenance of Gynodioecy. Key results Contrary to expectations if growth at high temperatures is stressful, we found that the hot treatment increased leaf chlorophyll content, decreased the percentage of plants that delayed flowering initiation, and did not affect the quantum efficiency of photosystem II. Growth at high temperatures did not affect the magnitude of the difference in rosette size (a correlate of flower number) between females and hermaphrodites, or the variance in pollen viability among hermaphrodites. Conclusions We found that growing-season temperatures typical of high female L. siphilitica populations were not stressful and did not affect either the fitness of females compared to hermaphrodites or variation in fitness among hermaphrodites. Consequently, further research is necessary to explain correlations between abiotic environmental factors and the frequency of females in this and other gynodioecious species.
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why is Gynodioecy a rare but widely distributed sexual system lessons from the lamiaceae
New Phytologist, 2016Co-Authors: Ruth L Rivkin, Andrea L Case, Christina M CarusoAbstract:Gynodioecy, a sexual system where females and hermaphrodites co-occur, is found in << 1% of angiosperm species. To understand why Gynodioecy is rare, we need to understand why females are maintained in some lineages, but not in others. We modelled the evolution of Gynodioecy in the Lamiaceae, and investigated whether transition rates between gynodioecious and nongynodioecious states varied across the family. We also investigated whether the evolution of Gynodioecy was correlated with the evolution of a herbaceous growth form and temperate distribution. Transition rates differed between Lamiaceae subfamilies. In the Nepetoideae, there were many transitions towards Gynodioecy (n = 11), but also many reversions to nonGynodioecy (n = 29). In addition, a herbaceous growth form, but not a temperate distribution, affected the rate of transitions both towards and away from Gynodioecy; transitions towards Gynodioecy occurred ˜16 times more frequently and transitions away from Gynodioecy occurred ˜11 times more frequently in herbaceous lineages than in woody lineages. Within the Lamiaceae, lineages in which Gynodioecy has frequently evolved also have a high rate of reversions to the nongynodioecious state. Consequently, to understand why Gynodioecy is rare, we need to understand why sexual systems are more evolutionarily labile in some lineages than in others.
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Why is Gynodioecy a rare but widely distributed sexual system? Lessons from the Lamiaceae.
New Phytologist, 2016Co-Authors: L. Ruth Rivkin, Andrea L Case, Christina M CarusoAbstract:Summary Gynodioecy, a sexual system where females and hermaphrodites co-occur, is found in
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AN ANGIOSPERM-WIDE ANALYSIS OF THE CORRELATES OF Gynodioecy
International Journal of Plant Sciences, 2016Co-Authors: Christina M Caruso, Katherine E. Eisen, Andrea L CaseAbstract:Premise of research. Gynodioecy, a dimorphic sexual system where individual plants are either female or hermaphroditic, has been documented in ≪1% of plant species. This rarity suggests that Gynodioecy can evolve and persist only under a restrictive set of conditions. One approach to determining these conditions is to identify the phenotypic traits and ecological factors that are associated with Gynodioecy, as such traits or factors may facilitate the evolution and persistence of the sexual system.Methodology. We assembled an angiosperm-wide database of gynodioecious species and used this database to test whether Gynodioecy was associated with two phenotypic traits/ecological factors: an herbaceous growth form and a temperate geographic distribution. Species-level analyses were used to confirm that gynodioecious species are predominately herbaceous and temperate. Family-level analyses were then used to test whether the presence of herbaceous and temperate species in a lineage was associated with the prese...
Tia-lynn Ashman - One of the best experts on this subject based on the ideXlab platform.
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Evolutionary pathways from hermaphroditism to separate sexes.
2014Co-Authors: Doris Bachtrog, Tia-lynn Ashman, Judith E. Mank, Catherine L. Peichel, Mark Kirkpatrick, Sarah P. Otto, Matthew W. Hahn, Jun Kitano, Itay Mayrose, Ray MingAbstract:Shown are two-step pathways involving intermediate male- and female-sterile individuals. Loss-of-function mutations (red) are assumed to be recessive, while gain-of-function mutations (green) are assumed to be dominant. Ancestral alleles are in black. M, male fertility allele; m, male sterility mutation; F, female fertility allele; f, female sterility mutation. Because loss of function mutations (red) are almost 50 times more frequent than gain of function mutations (green) in flowering plants, we would expect pathways 1 (e.g., some poplar species) or 2 (e.g., papaya) to arise earlier. Furthermore, transitions through Gynodioecy, pathways 2 and 3 (e.g., strawberry) allow females to completely avoid inbreeding depression, while transitions through androdioecy are more costly because males must compete with hermaphrodites for fertilization and do not have any of their own ovules to fertilize. These theoretical arguments help to account for the prevalence of Gynodioecy and the XY chromosome system (via pathway 2) observed in plants; nevertheless, all four pathways may be biologically relevant, although no known examples for pathway 4 currently exist.
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REVIEW: PART OF A SPECIAL ISSUE ON PLANT MATING SYSTEMS Gynodioecy to dioecy: are we there yet?
2012Co-Authors: Rachel B. Spigler, Tia-lynn AshmanAbstract:†Background The ‘Gynodioecy–dioecy pathway’ is considered to be one of the most important evolutionary routes from hermaphroditism to separate sexes (dioecy). Despite a large accumulation of evidence for female seed fertility advantages in gynodioecious species (females and hermaphrodites coexist) in support of the first step in the Gynodioecy–dioecy pathway, we still have very little evidence for the second step, i.e. the transition from Gynodioecy to dioecy. † Scope We review the literature to evaluate whether basic predictions by theory are supported. To establish whether females’ seed fertility advantage and frequencies are sufficient to favour the invasion of males, we review these for species along the Gynodioecy–dioecy pathway published in the last 5 years. We then review the empirical evidence for predictions deriving from the second step, i.e. hermaphrodites’ male fertility increases with female frequency, selection favours greater male fertility in hermaphrodites in gynodioecious species, and, where males and hermaphrodites coexist with females (subdioecy), males have greater male fertility than hermaphrodites. We review how genetic control and certain ecological features (pollen limitation, selfing, plasticity in sex expression and antagonists) influence the trajectory of a population along the Gynodioecy–dioecy pathway. †Conclusions Females tend to have greater seed fertility advantages over hermaphrodites where the two coexist, and this advantage is positively correlated with female frequency across species, as predicted by theory. A limited number of studies in subdioecious species have demonstrated that males have an advantage over hermaphrodites, as also predicted by theory. However, less evidence exists for phenotypic selection to increase male traits of hermaphrodites or for increasing male function of hermaphrodites in populations with high female frequency. A few key case studies underline the importance of examining multiple components of male fertility and the roles of pollen limitation, selfing and plasticity, when evaluating advantages. We conclude that we do not yet have a full understanding of the transition from Gynodioecy to dioecy.
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PART OF A SPECIAL ISSUE ON PLANT MATING SYSTEMS Functional characterization of Gynodioecy in Fragaria vesca ssp. bracteata (Rosaceae)
2012Co-Authors: Matthew H. Koski, Tia-lynn AshmanAbstract:†Background and Aims Gynodioecy is a phylogenetically widespread and important sexual system where females coexist with hermaphrodites. Because dioecy can arise from Gynodioecy, characterization of Gynodioecy in close relatives of dioecious and sub-dioecious species can provide insight into this transition. Thus, we sought to determine whether Fragaria vesca ssp. bracteata, a close relative to F. chiloensis and F. virginiana, exhibits the functional and population genetic hallmarks of a gynodioecious species. †Methods We compared reproductive allocation of females and hermaphrodites grown in the greenhouse and estimated genetic diversity (allelic diversity, heterozygosity) and inbreeding coefficients for field-collected adults of both sexes using simple sequence repeat (SSR) markers. We estimated mating system and early seed fitness from open-pollinated families of both sex morphs. †Key Results Under greenhouse conditions, females and hermaphrodites allocated similarly to all reproductive traits except flower number, and, as a consequence, females produced 30 % fewer seeds per plant than hermaphrodites. Under natural conditions, hermaphrodites produce seeds by self-fertilization approx. 75 % of the time, and females produced outcrossed seeds with very little biparental inbreeding. Consistent with inbreeding depression, seeds from open-pollinated hermaphrodites were less likely to germinate than those from females, and family-level estimates of hermaphrodite selfing rates were negatively correlated with germination success and speed. Furthermore, estimates of inbreeding depression based on genetic markers and population genetic theory indicate that inbreeding depression in the field could be high. †Conclusions The joint consideration of allocation and mating system suggests that compensation may be sufficient to maintain females given the current understanding of sex determination. Fragaria vesca ssp. bracteata exhibited similar sex morph-dependent patterns of mating system and genetic diversity, but less reproductive trait dimorphism, than its sub-dioecious and dioecious congeners.
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Functional characterization of Gynodioecy in Fragaria vesca ssp. bracteata (Rosaceae).
Annals of botany, 2011Co-Authors: Matthew H. Koski, Tia-lynn AshmanAbstract:BACKGROUND AND AIMS: Gynodioecy is a phylogenetically widespread and important sexual system where females coexist with hermaphrodites. Because dioecy can arise from Gynodioecy, characterization of Gynodioecy in close relatives of dioecious and sub-dioecious species can provide insight into this transition. Thus, we sought to determine whether Fragaria vesca ssp. bracteata, a close relative to F. chiloensis and F. virginiana, exhibits the functional and population genetic hallmarks of a gynodioecious species. METHODS: We compared reproductive allocation of females and hermaphrodites grown in the greenhouse and estimated genetic diversity (allelic diversity, heterozygosity) and inbreeding coefficients for field-collected adults of both sexes using simple sequence repeat (SSR) markers. We estimated mating system and early seed fitness from open-pollinated families of both sex morphs. KEY RESULTS: Under greenhouse conditions, females and hermaphrodites allocated similarly to all reproductive traits except flower number, and, as a consequence, females produced 30 % fewer seeds per plant than hermaphrodites. Under natural conditions, hermaphrodites produce seeds by self-fertilization approx. 75 % of the time, and females produced outcrossed seeds with very little biparental inbreeding. Consistent with inbreeding depression, seeds from open-pollinated hermaphrodites were less likely to germinate than those from females, and family-level estimates of hermaphrodite selfing rates were negatively correlated with germination success and speed. Furthermore, estimates of inbreeding depression based on genetic markers and population genetic theory indicate that inbreeding depression in the field could be high. CONCLUSIONS: The joint consideration of allocation and mating system suggests that compensation may be sufficient to maintain females given the current understanding of sex determination. Fragaria vesca ssp. bracteata exhibited similar sex morph-dependent patterns of mating system and genetic diversity, but less reproductive trait dimorphism, than its sub-dioecious and dioecious congeners.
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Gynodioecy to dioecy: are we there yet?
Annals of botany, 2011Co-Authors: Rachel B. Spigler, Tia-lynn AshmanAbstract:BACKGROUND The 'Gynodioecy-dioecy pathway' is considered to be one of the most important evolutionary routes from hermaphroditism to separate sexes (dioecy). Despite a large accumulation of evidence for female seed fertility advantages in gynodioecious species (females and hermaphrodites coexist) in support of the first step in the Gynodioecy-dioecy pathway, we still have very little evidence for the second step, i.e. the transition from Gynodioecy to dioecy. SCOPE We review the literature to evaluate whether basic predictions by theory are supported. To establish whether females' seed fertility advantage and frequencies are sufficient to favour the invasion of males, we review these for species along the Gynodioecy-dioecy pathway published in the last 5 years. We then review the empirical evidence for predictions deriving from the second step, i.e. hermaphrodites' male fertility increases with female frequency, selection favours greater male fertility in hermaphrodites in gynodioecious species, and, where males and hermaphrodites coexist with females (subdioecy), males have greater male fertility than hermaphrodites. We review how genetic control and certain ecological features (pollen limitation, selfing, plasticity in sex expression and antagonists) influence the trajectory of a population along the Gynodioecy-dioecy pathway. CONCLUSIONS Females tend to have greater seed fertility advantages over hermaphrodites where the two coexist, and this advantage is positively correlated with female frequency across species, as predicted by theory. A limited number of studies in subdioecious species have demonstrated that males have an advantage over hermaphrodites, as also predicted by theory. However, less evidence exists for phenotypic selection to increase male traits of hermaphrodites or for increasing male function of hermaphrodites in populations with high female frequency. A few key case studies underline the importance of examining multiple components of male fertility and the roles of pollen limitation, selfing and plasticity, when evaluating advantages. We conclude that we do not yet have a full understanding of the transition from Gynodioecy to dioecy.
M.f. Bailey - One of the best experts on this subject based on the ideXlab platform.
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Physiological effects of temperature do not explain prevalence of females in populations of gynodioecious Lobelia siphilitica growing in warmer climates.
American journal of botany, 2017Co-Authors: M.f. Bailey, Andrea L Case, Christina M CarusoAbstract:Premise of the study Gynodioecy is a sexual polymorphism whereby female and hermaphroditic plants co-occur within populations. In many gynodioecious species, stressful abiotic environments are associated with higher frequencies of females. This association suggests that abiotic stress affects the relative fitness of females and hermaphrodites and, thus, the maintenance of Gynodioecy. Methods To test whether abiotic stress affects the fitness of females and hermaphrodites, we grew open-pollinated Lobelia siphilitica families in temperature regimes characteristic of the southern portion of the species' range (where females are common) and the northern portion of the range (where females are rare). We measured physiological and phenological traits that are indicative of heat stress, and fitness components of females and hermaphrodites that could affect the maintenance of Gynodioecy. Key results Contrary to expectations if growth at high temperatures is stressful, we found that the hot treatment increased leaf chlorophyll content, decreased the percentage of plants that delayed flowering initiation, and did not affect the quantum efficiency of photosystem II. Growth at high temperatures did not affect the magnitude of the difference in rosette size (a correlate of flower number) between females and hermaphrodites, or the variance in pollen viability among hermaphrodites. Conclusions We found that growing-season temperatures typical of high female L. siphilitica populations were not stressful and did not affect either the fitness of females compared to hermaphrodites or variation in fitness among hermaphrodites. Consequently, further research is necessary to explain correlations between abiotic environmental factors and the frequency of females in this and other gynodioecious species.
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Evaluation of the cost of restoration of male fertility in Brassica napus
Botany, 2014Co-Authors: Benjamin R. Montgomery, M.f. Bailey, Gregory G. Brown, Lynda F. DelphAbstract:Gynodioecy frequently results from the interplay of mitochondrial cytoplasmic male sterility (CMS) and nuclear fertility-restoration genes. Models suggest that maintaining cytonuclear Gynodioecy requires that restorer genes incur a cost to fitness because otherwise they would increase toward fixation. Direct tests of costs of restorer alleles require knowledge of the underlying genetics of sex determination. We use a well characterized CMS system in Brassica napus L. to measure aspects of fitness in four lineages that vary in whether they carry the pol CMS gene or male-fertile cytoplasm (cam), and whether they carry the Rfp restorer of pol or Rfn restorer of the nap CMS gene. As expected, plants with pol CMS and only the Rfn restorer experienced reduced flower size, stamen length, and pollen counts. Plants with pol and the Rfp restorer showed incomplete restoration with shorter stamens than both lines with cam cytoplasm and reduced pollen counts compared with plants with cam cytoplasm and the Rfp restorer...
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Recent advances in the study of Gynodioecy: the interface of theory and empiricism.
Annals of botany, 2009Co-Authors: David E Mccauley, M.f. BaileyAbstract:†Background In this review we report on recent literature concerned with studies of Gynodioecy, or the cooccurrence of female and hermaphrodite individuals in natural plant populations. Rather than review this literature initsentirety,ourfocusisontheinterplaybetweentheoreticalandempiricalapproachestothestudyofGynodioecy. †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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Merging theory and mechanism in studies of Gynodioecy.
Trends in Ecology and Evolution, 2007Co-Authors: L.f. Delph, Pascal Touzet, M.f. BaileyAbstract:In gynodioecious species females and hermaphrodites coexist and the genetics of sex determination is usually nuclear-cytoplasmic. Maintaining nuclear-cytoplasmic Gynodioecy requires polymorphism for both the feminizing genes (contained in the mitochondria) and the genes that restore male fertility (contained in the nucleus). This complex polymorphism depends in part on there being negative pleiotropic effects (costs) of the nuclear restorer alleles. We combine information from theoretical studies and studies on the molecular action of restorers in crops to interpret the likely costs of restorer alleles, and suggest how various aspects of the theoretical models could be tested. In doing so we highlight how crops can be used to address evolutionary questions about the maintenance of nuclear-cytoplasmic Gynodioecy.
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Merging theory and mechanism in studies of Gynodioecy
Trends in ecology & evolution, 2006Co-Authors: Lynda F. Delph, Pascal Touzet, M.f. BaileyAbstract:In gynodioecious species, females and hermaphrodites coexist and the genetics of sex determination is usually nuclear cytoplasmic. Maintaining nuclear-cytoplasmic Gynodioecy requires polymorphism for the feminizing genes (contained in the mitochondria) and the genes that restore male fertility (contained in the nucleus). This complex polymorphism depends, in part, on there being negative pleiotropic effects (i.e. costs) of the nuclear restorer alleles. Here, we combine information from theoretical studies and studies on the molecular action of restorer alleles in crops to interpret the probable costs of such alleles, and suggest how various aspects of the theoretical models could be tested. In doing so, we highlight how crops can be used to address evolutionary questions about the maintenance of nuclear-cytoplasmic Gynodioecy.
Mathilde Dufay - One of the best experts on this subject based on the ideXlab platform.
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Sex-specific fitness variation in gynodioecious Beta vulgaris ssp. maritima: do empirical observations fit theoretical predictions?
2014Co-Authors: I De Cauwer, -f. J. Arnaud, A. Courseaux, Mathilde DufayAbstract:Flowering plant species exhibit a large range of repro-ductive strategies. After hermaphroditism, Gynodioecy is one of the most common breeding systems (Webb, 1999). In gynodioecious species, two sexual phenotype
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An angiosperm-wide analysis of the Gynodioecy–dioecy pathway
Annals of botany, 2014Co-Authors: Mathilde Dufay, P. Champelovier, Jos Käfer, Jean-pierre Henry, Sylvain Mousset, Gabriel A. B. MaraisAbstract:† Background and Aims About 6 % of an estimated total of 240 000 species of angiosperms are dioecious. The main precursors of this sexual system are thought to be monoecy and Gynodioecy. A previous angiosperm-wide study revealed that many dioecious species have evolved through the monoecy pathway; some case studies and a large body of theoretical research also provide evidence in support of the Gynodioecy pathway. If plants have evolved through the Gynodioecy pathway, gynodioecious and dioecious species should co-occur in the same genera. However, to date, no large-scale analysis has been conducted to determine the prevalence of the Gynodioecy pathway in angiosperms. In this study, this gap in knowledge was addressed by performing an angiosperm-wide survey in order to test for co-occurrence as evidence of the Gynodioecy pathway. † Methods Data from different sources were compiled to obtain (to our knowledge) the largest dataset on Gynodioecy available, with 275 genera that include at least one gynodioecious species. This dataset was combined with a dioecy dataset from the literature, and a study was made of how often dioecious and gynodioecious species could be found in the same genera using a contingency table framework. † Key Results It was found that, overall, angiosperm genera with both gynodioecious and dioecious species occur more frequently than expected, in agreement with the Gynodioecy pathway. Importantly, this trend holds when studying different classes separately (or sub-classes, orders and families), suggesting that the Gynodioecy pathway is not restricted to a few taxa but may instead be widespread in angiosperms. † Conclusions This work complements that previously carried out on the monoecy pathway and suggests that Gynodioecy is also a common pathway in angiosperms. The results also identify angiosperm families where some (or all) dioecious species may have evolved from gynodioecious precursors. These families could be the targets of future small-scale studies on transitions to dioecy taking phylogeny explicitly into account.
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An angiosperm-wide analysis of the Gynodioecy-dioecy pathway.
Annals of Botany, 2014Co-Authors: Mathilde Dufay, P. Champelovier, Jos Käfer, Jean-pierre Henry, Sylvain Mousset, Gabriel MaraisAbstract:BACKGROUND AND AIMS: About 6 % of an estimated total of 240 000 species of angiosperms are dioecious. The main precursors of this sexual system are thought to be monoecy and Gynodioecy. A previous angiosperm-wide study revealed that many dioecious species have evolved through the monoecy pathway; some case studies and a large body of theoretical research also provide evidence in support of the Gynodioecy pathway. If plants have evolved through the Gynodioecy pathway, gynodioecious and dioecious species should co-occur in the same genera. However, to date, no large-scale analysis has been conducted to determine the prevalence of the Gynodioecy pathway in angiosperms. In this study, this gap in knowledge was addressed by performing an angiosperm-wide survey in order to test for co-occurrence as evidence of the Gynodioecy pathway.\n\nMETHODS: Data from different sources were compiled to obtain (to our knowledge) the largest dataset on Gynodioecy available, with 275 genera that include at least one gynodioecious species. This dataset was combined with a dioecy dataset from the literature, and a study was made of how often dioecious and gynodioecious species could be found in the same genera using a contingency table framework.\n\nKEY RESULTS: It was found that, overall, angiosperm genera with both gynodioecious and dioecious species occur more frequently than expected, in agreement with the Gynodioecy pathway. Importantly, this trend holds when studying different classes separately (or sub-classes, orders and families), suggesting that the Gynodioecy pathway is not restricted to a few taxa but may instead be widespread in angiosperms.\n\nCONCLUSIONS: This work complements that previously carried out on the monoecy pathway and suggests that Gynodioecy is also a common pathway in angiosperms. The results also identify angiosperm families where some (or all) dioecious species may have evolved from gynodioecious precursors. These families could be the targets of future small-scale studies on transitions to dioecy taking phylogeny explicitly into account.
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how selfing inbreeding depression and pollen limitation impact nuclear cytoplasmic Gynodioecy a model
Evolution, 2013Co-Authors: Antoine Dornier, Mathilde DufayAbstract:: Gynodioecy, the co-occurrence of females and hermaphrodites, is often due to conflicting interactions between cytoplasmic male sterility genes and nuclear restorers. Although Gynodioecy often occurs in self-compatible species, the effect of self-pollination, inbreeding depression, and pollen limitation acting differently on females and hermaphrodites remains poorly known in the case of nuclear-cytoplasmic Gynodioecy (NCG). In this study, we model NCG in an infinite population and we study the effect of selfing rate, inbreeding depression, and pollen limitation on the maintenance of Gynodioecy and on sex ratios at equilibrium. We found that selfing and inbreeding depression have a strong impact, which depends on whether restorer cost acts on male or female fitness. When cost affects male fitness, the strength of cost has no effect, whereas selfing and inbreeding depression only impact Gynodioecy by modifying the value of the female advantage. When cost affects female fitness, selfing facilitates NCG and reduces the role of strength of the cost, even when no inbreeding depression occurs, whereas inbreeding depression globally restricts the maintenance of the polymorphism. Finally, we found that pollen limitation could additionally strongly modify the dynamic of Gynodioecy. We discuss our findings in the light of empirical data available in gynodioecious species.
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AND POLLEN LIMITATION IMPACT NUCLEAR-CYTOPLASMIC Gynodioecy: A MODEL
2012Co-Authors: How Selfing, Antoine Dornier, Mathilde DufayAbstract:Gynodioecy, the co-occurrence of females and hermaphrodites, is often due to conflicting interactions between cytoplasmic male sterility genes and nuclear restorers. Although Gynodioecy often occurs in self-compatible species, the effect of self-pollination, inbreeding depression, and pollen limitation acting differently on females and hermaphrodites remains poorly known in the case of nuclear-cytoplasmic Gynodioecy (NCG). In this study, we model NCG in an infinite population and we study the effect of selfing rate, inbreeding depression, and pollen limitation on the maintenance of Gynodioecy and on sex ratios at equilibrium. We found that selfing and inbreeding depression have a strong impact, which depends on whether restorer cost acts on male or female fitness. When cost affects male fitness, the strength of cost has no effect, whereas selfing and inbreeding depression only impact Gynodioecy by modifying the value of the female advantage. When cost affects female fitness, selfing facilitates NCG and reduces the role of strength of the cost, even when no inbreeding depression occurs, whereas inbreeding depression globally restricts the maintenance of the polymorphism. Finally, we found that pollen limitation could additionally strongly modify the dynamic of Gynodioecy. We discuss our findings in the light of empirical data available in gynodioecious species. KEY WORDS: Cost of restorer, cytoplasmicmale sterility, female advantage, Gynodioecy, inbreeding depression, pollen limitation, self-fertilization. Gynodioecy, the co-occurrence of females and hermaphrodites within the same species has been a fascinating object of inter
J. Cuguen - One of the best experts on this subject based on the ideXlab platform.
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Modelling the maintenance of a male fertile cytoplasm in a gynodioecious population
Heredity, 2007Co-Authors: Mathilde Dufay, Pascal Touzet, S. Maurice, J. CuguenAbstract:Gynodioecy is the co-occurrence of females and hermaphrodites in populations. It is usually due to the combined action of cytoplasmic male sterility (CMS) genes and nuclear genes that restore male fertility. According to previous theoretical studies, it is very difficult to explain the maintenance of Gynodioecy with CMS and male-fertile cytotypes, although it has been observed in some species. However, only very specific situations have been investigated so far. We present a model to investigate the conditions that promote the maintenance of this breeding system in the case of an outcrossed species when CMS and male-fertile (non-CMS) cytotypes are present in an infinite panmictic population. We show that the type of cost of restoration strongly affects the conditions for stable maintenance of Gynodioecy. Stable nuclear-cytoplasmic Gynodioecy requires a female advantage, which is a classical condition for Gynodioecy, but also a cost of CMS for female fitness, which had been rarely investigated. A cost of restoration is also needed, which could affect either pollen or seeds. Finally, we found that Gynodioecy was attainable for a large set of parameter values, including low differences in fitness among genotypes and phenotypes. Our theoretical predictions are compared with previous theoretical work and with results of empirical studies on various gynodioecious species.
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Emergence of Gynodioecy in wild beet (Beta vulgaris ssp. maritima L.): a genealogical approach using chloroplastic nucleotide sequences.
Proceedings of the Royal Society B: Biological Sciences, 2006Co-Authors: S. Fénart, Pascal Touzet, J.-f. Arnaud, J. CuguenAbstract:Gynodioecy is a breeding system where both hermaphroditic and female individuals coexist within plant populations. This dimorphism is the result of a genomic interaction between maternally inherited cytoplasmic male sterility (CMS) genes and bi-parentally inherited nuclear male fertility restorers. As opposed to other gynodioecious species, where every cytoplasm seems to be associated with male sterility, wild beet Beta vulgaris ssp. maritima exhibits a minority of sterilizing cytoplasms among numerous nonsterilizing ones. Many studies on population genetics have explored the molecular diversity of different CMS cytoplasms, but questions remain concerning their evolutionary dynamics. In this paper we report one of the first investigations on phylogenetic relationships between CMS and non-CMS lineages. We investigated the phylogenetic relationships between 35 individuals exhibiting different mitochondrial haplotypes. Relying on the high linkage disequilibrium between chloroplastic and mitochondrial genomes, we chose to analyse the nucleotide sequence diversity of three chloroplastic fragments (trnK intron, trnD– trnT and trnL–trnF intergenic spacers). Nucleotide diversity appeared to be low, suggesting a recent bottleneck during the evolutionary history of B. vulgaris ssp. maritima. Statistical parsimony analyses revealed a star-like genealogy and showed that sterilizing haplotypes all belong to different lineages derived from an ancestral non-sterilizing cytoplasm. These results suggest a rapid evolution of male sterility in this taxon. The emergence of Gynodioecy in wild beet is confronted with theoretical expectations, describing either Gynodioecy dynamics as the maintenance of CMS factors through balancing selection or as a constant turnover of new CMSs