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Spencer C H Barrett - One of the best experts on this subject based on the ideXlab platform.
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The role of hybridization in the evolution of Sexual system diversity in a clonal, aquatic plant
Evolution, 2016Co-Authors: Sarah B. Yakimowski, Spencer C H BarrettAbstract:: The stable coexistence within populations of females, males, and hermaphrodites (subdioecy) is enigmatic because theoretical models indicate that maintenance of this Sexual system involves highly restricted conditions. Subdioecy is more commonly interpreted as a transitory stage along the gynodioecious pathway from hermaphroditism to dioecy. The widespread, North American, aquatic plant Sagittaria latifolia is largely composed of monoecious or dioecious populations; however, subdioecious populations with high frequencies of hermaphrodites (mean frequency = 0.50) characterize the northern range boundary of dioecy in eastern North America. We investigated two hypotheses for the origin of subdioecy in this region. Using polymorphic microsatellite loci, we evaluated whether subdioecy arises through selection on standing genetic variation for male sex inconstancy in dioecious populations, or results from hybridization between monoecious and dioecious populations. We found evidence for both pathways to subdioecy, although hybridization was the more common mechanism, with genetic evidence of admixture in nine of 14 subdioecious populations examined. Hybridization has also played a role in the origin of androdioecious populations in S. latifolia, a mechanism not often considered in the evolution of this rare Sexual system. Our study demonstrates how hybridization has the potential to play a role in the diversification of plant Sexual Systems.
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ecological genetics of sex ratios in plant populations
Philosophical Transactions of the Royal Society B, 2010Co-Authors: Spencer C H Barrett, Sarah B. Yakimowski, David L Field, Melinda PickupAbstract:In many angiosperm species, populations are reproductively subdivided into distinct Sexual morphs including females, males and hermaphrodites. Sexual polymorphism is maintained by frequency-dependent selection, leading to predictable sex ratios at equilibrium. Charles Darwin devoted much of his book ‘ The Different Forms of Flowers on Plants of the Same Species ’ (1877) to investigating plant Sexual polymorphisms and laid the foundation for many problems addressed today by integrating theory with empirical studies of the demography and genetics of populations. Here, we summarize our recent work on the ecological and genetic mechanisms influencing variation in sex ratios and their implications for evolutionary transitions among Sexual Systems. We present the results of a survey of sex ratios from 126 species from 47 angiosperm families and then address two general problems using examples from diverse angiosperm taxa: (i) the mechanisms governing biased sex ratios in dioecious species; (ii) the origins and maintenance of populations composed of females, males and hermaphrodites. Several themes are emphasized, including the importance of non-equilibrium conditions, the role of life history and demography in affecting sex ratios, the value of theory for modelling the dynamics of sex ratio variation, and the utility of genetic markers for investigating evolutionary processes in Sexually polymorphic plant populations.
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a phylogenetic study of evolutionary transitions in Sexual Systems in australasian wurmbea colchicaceae
International Journal of Plant Sciences, 2008Co-Authors: Andrea L. Case, Sean W Graham, Terry D Macfarlane, Spencer C H BarrettAbstract:Using phylogenies to make sound inferences about character evolution depends on a variety of factors, including tree uncertainty, taxon sampling, and the degree of evolutionary lability in the character of interest. We explore the effect of these and other sources of ambiguity for maximum likelihood (ML)–based inferences of Sexual‐system evolution in Wurmbea, a small genus of geophytic monocots from the Southern Hemisphere. We reconstructed Wurmbea phylogeny using four noncontiguous regions (ca. 5.5 kb) of the plastid genome across a broad sampling of taxa, and we confirm that the genus is divided into two well‐supported clades, each defined by its geography (Africa vs. Australasia) and variation in Sexual system (i.e., uniformly monomorphic vs. Sexually variable, respectively). We demonstrate that the predominantly Australian clade includes the Sexually monomorphic species Iphigenia novae‐zelandiae. We observe treewide uncertainty in the state of all ancestral nodes, and therefore all state transitions, ...
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the evolution of polymorphic Sexual Systems in daffodils narcissus
New Phytologist, 2004Co-Authors: Spencer C H Barrett, Lawrence D HarderAbstract:Summary Narcissus, the daffodil genus, exhibits an unusual diversity of Sexual Systems, with populations that are monomorphic, dimorphic or trimorphic for style length. Associated with this variation are striking differences among species in floral morphology and pollination biology. This diversity provides an opportunity to investigate the evolution of mating polymorphisms, and to determine how floral morphology promotes transitions among Sexual Systems. Because of the absence of heteromorphic incompatibility in Narcissus, floral morphology plays a key role in governing patterns of outcrossed mating. Phylogenetic evidence indicates that stylar monomorphism is ancestral in the genus, with multiple origins of stylar polymorphism, including independent origins of stigma-height dimorphism, distyly and tristyly. Sexual polymorphisms have evolved only in lineages with narrow floral tubes that are pollinated by Lepidoptera and/or long-tongued bees. Populations of polymorphic Narcissus species are typically dominated by the long-styled morph and display imperfect reciprocity in the positions of Sexual organs. These features are consequences of the unusual association between stylar polymorphism and a self-incompatibility system that permits intramorph mating.
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chloroplast haplotype variation among monoecious and dioecious populations of sagittaria latifolia alismataceae in eastern north america
Molecular Ecology, 2004Co-Authors: Marcel E Dorken, Spencer C H BarrettAbstract:Aquatic plants commonly have extensive geographical distributions, implying few restrictions to dispersal. Here we investigate the postglacial history of an aquatic plant with contrasting Sexual Systems (monoecy and dioecy), which are predicted to affect dispersal ability. We examined the distribution of cpDNA haplotypes using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) among 76 populations (32 monoecious, 38 dioecious, two mixed and four undetermined populations) of Sagittaria latifolia sampled throughout eastern North America. We also use these data to investigate the polarity of the evolutionary transition between monoecy and dioecy. Using PCR–RFLP, we identified eight cpDNA haplotypes. All haplotypes were found in unglaciated areas of the species’ range, clustered primarily in the southeastern United States, providing evidence that glacial refugia probably occurred in this area. Genetic diversity ( h T ) was more than six times greater among monoecious compared to dioecious populations. All seven of the haplotypes for which the Sexual system could be determined were represented among monoecious populations. In contrast, only four haplotypes were detected in dioecious populations and 94% of individuals from dioecious populations possessed a single haplotype. Monoecious populations possessing this widespread haplotype were restricted to the southern portion of the range, indicating that dioecy probably originated in this region and then spread northwards. The distribution of cpDNA haplotypes in dioecious populations represents a subset of the variation found in monoecious populations, a pattern expected if dioecy has evolved from monoecy in S. latifolia .
Marcel E Dorken - One of the best experts on this subject based on the ideXlab platform.
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small scale and regional spatial dynamics of an annual plant with contrasting Sexual Systems
Journal of Ecology, 2017Co-Authors: Marcel E Dorken, Robert P Freckleton, John R PannellAbstract:1. Plant demography is known to depend on both spatial dynamics and life history, but how these two factors interact is poorly understood. We conducted a longitudinal study of the wind-pollinated annual plant Mercurialis annua that varies geographically in its Sexual system to investigate this interaction. 2. Metapopulation demographic models predict that regular population turnover should be a more common feature of monomorphic than dimorphic populations because males and females cannot found new populations by selfing but hermaphrodites can. We tested the prediction that rates of population turnover would be higher in monomorphic compared to dimorphic regions. 3. We surveyed 356 populations of M. annua along five regional transects in Morocco and the Iberian Peninsula over a 3-year period to examine their demography and persistence. Each transect crossed a transition in the Sexual system, from a monomorphic region where almost all populations were hermaphroditic to a dimorphic one in which most populations had separate sexes (males with females or hermaphrodites). 4. As predicted, rates of local apparent extinctions (i.e., the disappearance of adult plants) were nearly 50% higher in monomorphic compared to dimorphic regions. Local extinctions appeared to be driven by changes in vegetation cover, with extinctions tending to occur in sites in which perennial cover also declined. This suggests that disturbance is a primary agent of local extinctions. 5. We further examined the influence of regional dynamics on local demographic properties by investigating patterns of spatial autocorrelation in population density across years. We found positive spatial autocorrelations in plant densities within regions for both Sexual Systems. However, these positive autocorrelations extended over shorter distances in monomorphic regions, perhaps as a result of greater population flux in these regions. 6. Synthesis. Our study shows that population dynamics may be influenced by processes acting at a range of spatial scales: within patches, across patches within sites, and across sites within regions, as well as by life-history variation. In Mercurialis annua, regional variation in apparent extinction rates is affected by life history and implicated in regulating the geographical distribution of populations with different Sexual Systems.
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Small‐scale and regional spatial dynamics of an annual plant with contrasting Sexual Systems
Journal of Ecology, 2017Co-Authors: Marcel E Dorken, Robert P Freckleton, John R PannellAbstract:1. Plant demography is known to depend on both spatial dynamics and life history, but how these two factors interact is poorly understood. We conducted a longitudinal study of the wind-pollinated annual plant Mercurialis annua that varies geographically in its Sexual system to investigate this interaction. 2. Metapopulation demographic models predict that regular population turnover should be a more common feature of monomorphic than dimorphic populations because males and females cannot found new populations by selfing but hermaphrodites can. We tested the prediction that rates of population turnover would be higher in monomorphic compared to dimorphic regions. 3. We surveyed 356 populations of M. annua along five regional transects in Morocco and the Iberian Peninsula over a 3-year period to examine their demography and persistence. Each transect crossed a transition in the Sexual system, from a monomorphic region where almost all populations were hermaphroditic to a dimorphic one in which most populations had separate sexes (males with females or hermaphrodites). 4. As predicted, rates of local apparent extinctions (i.e., the disappearance of adult plants) were nearly 50% higher in monomorphic compared to dimorphic regions. Local extinctions appeared to be driven by changes in vegetation cover, with extinctions tending to occur in sites in which perennial cover also declined. This suggests that disturbance is a primary agent of local extinctions. 5. We further examined the influence of regional dynamics on local demographic properties by investigating patterns of spatial autocorrelation in population density across years. We found positive spatial autocorrelations in plant densities within regions for both Sexual Systems. However, these positive autocorrelations extended over shorter distances in monomorphic regions, perhaps as a result of greater population flux in these regions. 6. Synthesis. Our study shows that population dynamics may be influenced by processes acting at a range of spatial scales: within patches, across patches within sites, and across sites within regions, as well as by life-history variation. In Mercurialis annua, regional variation in apparent extinction rates is affected by life history and implicated in regulating the geographical distribution of populations with different Sexual Systems.
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gender variation and transitions between Sexual Systems in mercurialis annua euphorbiaceae
International Journal of Plant Sciences, 2008Co-Authors: John R Pannell, Marcel E Dorken, Benoit Pujol, Regina BerjanoAbstract:Evolutionary transitions between hermaphroditism and dioecy have occurred numerous times in the land plants. We briefly review the factors thought to be responsible for these transitions, and we provide a synthesis of what has been learned from recent studies of the annual herb Mercurialis annua, in which dioecy (males and females), monoecy (functional hermaphrodites), and androdioecy (males and hermaphrodites) occur in different parts of its geographic range. Previous research on M. annua has revealed the importance of genome duplication and hybridization in the origin of much of the observed variation. Here we show, however, that spatial transitions in the Sexual system also occur within the same ploidy level. In particular, we present an analysis, using flow cytometry data, of ploidy variation across a previously unstudied transition between hermaphroditism and androdioecy, in which we find that the Sexual‐system transition is uncoupled from the shift in ploidy levels. We review recent research that sh...
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colonisation as a common denominator in plant metapopulations and range expansions effects on genetic diversity and Sexual Systems
Landscape Ecology, 2006Co-Authors: John R Pannell, Marcel E DorkenAbstract:Colonisation plays a central role in both the initial occupancy of a region through range expansions as well as in metapopulations, where local extinctions are balanced by re-colonisations. In this paper, we review the effects that colonisation is expected to have on patterns of genetic variation within a species, and we draw attention to the possibility of interpreting these patterns as signatures of colonisation in the past. We briefly review theoretical predictions for the effect of colonisation on both neutral genetic diversity and on variation at genetic loci that regulate the Sexual system of plant populations. The Sexual system represents a particularly important trait in this context because it is affected by both selection during colonisation, and because it influences gene flow amongst populations. Finally, we introduce four case studies of plant species that show variation in their Sexual Systems that is consistent with theoretical predictions.
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chloroplast haplotype variation among monoecious and dioecious populations of sagittaria latifolia alismataceae in eastern north america
Molecular Ecology, 2004Co-Authors: Marcel E Dorken, Spencer C H BarrettAbstract:Aquatic plants commonly have extensive geographical distributions, implying few restrictions to dispersal. Here we investigate the postglacial history of an aquatic plant with contrasting Sexual Systems (monoecy and dioecy), which are predicted to affect dispersal ability. We examined the distribution of cpDNA haplotypes using polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) among 76 populations (32 monoecious, 38 dioecious, two mixed and four undetermined populations) of Sagittaria latifolia sampled throughout eastern North America. We also use these data to investigate the polarity of the evolutionary transition between monoecy and dioecy. Using PCR–RFLP, we identified eight cpDNA haplotypes. All haplotypes were found in unglaciated areas of the species’ range, clustered primarily in the southeastern United States, providing evidence that glacial refugia probably occurred in this area. Genetic diversity ( h T ) was more than six times greater among monoecious compared to dioecious populations. All seven of the haplotypes for which the Sexual system could be determined were represented among monoecious populations. In contrast, only four haplotypes were detected in dioecious populations and 94% of individuals from dioecious populations possessed a single haplotype. Monoecious populations possessing this widespread haplotype were restricted to the southern portion of the range, indicating that dioecy probably originated in this region and then spread northwards. The distribution of cpDNA haplotypes in dioecious populations represents a subset of the variation found in monoecious populations, a pattern expected if dioecy has evolved from monoecy in S. latifolia .
Ray Ming - One of the best experts on this subject based on the ideXlab platform.
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macroevolutionary synthesis of flowering plant Sexual Systems
Evolution, 2017Co-Authors: Emma E Goldberg, Itay Mayrose, Ray Ming, Sarah P Otto, Jana C Vamosi, Niv Sabath, Tialynn AshmanAbstract:Sexual system is a key determinant of genetic variation and reproductive success, affecting evolution within populations and within clades. Much research in plants has focused on evolutionary transitions away from the most common state of hermaphroditism and toward the rare state of dioecy (separate sexes). Rather than transitions predominantly toward greater Sexual differentiation, however, evolution may proceed in the direction of lesser Sexual differentiation. We analyzed the macroevolutionary dynamics of Sexual system in angiosperm genera that contain both dioecious and non-dioecious species. Our phylogenetic analyses encompass a total of 2145 species from 40 genera. Overall, we found little evidence that rates of Sexual system transitions are greater in any direction. Counting the number of inferred state changes revealed a mild prevalence of transitions away from hermaphroditism and away from dioecy, toward states of intermediate Sexual differentiation. We identify genera in which future studies of Sexual system evolution might be especially productive, and we discuss how integrating genetic or population-level studies of Sexual system could improve the power of phylogenetic comparative analyses. Our work adds to the evidence that different selective pressures and constraints act in different groups, helping maintain the variety of Sexual Systems observed among plants. This article is protected by copyright. All rights reserved
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tree of sex a database of Sexual Systems
Scientific Data, 2014Co-Authors: Tialynn Ashman, Doris Bachtrog, Heath Blackmon, Emma E Goldberg, Matthew W Hahn, Mark Kirkpatrick, Jun Kitano, Judith E Mank, Itay Mayrose, Ray MingAbstract:The vast majority of eukaryotic organisms reproduce Sexually, yet the nature of the Sexual system and the mechanism of sex determination often vary remarkably, even among closely related species. Some species of animals and plants change sex across their lifespan, some contain hermaphrodites as well as males and females, some determine sex with highly differentiated chromosomes, while others determine sex according to their environment. Testing evolutionary hypotheses regarding the causes and consequences of this diversity requires interspecific data placed in a phylogenetic context. Such comparative studies have been hampered by the lack of accessible data listing Sexual Systems and sex determination mechanisms across the eukaryotic tree of life. Here, we describe a database developed to facilitate access to Sexual system and sex chromosome information, with data on Sexual Systems from 11,038 plant, 705 fish, 173 amphibian, 593 non-avian reptilian, 195 avian, 479 mammalian, and 11,556 invertebrate species.
John R Pannell - One of the best experts on this subject based on the ideXlab platform.
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small scale and regional spatial dynamics of an annual plant with contrasting Sexual Systems
Journal of Ecology, 2017Co-Authors: Marcel E Dorken, Robert P Freckleton, John R PannellAbstract:1. Plant demography is known to depend on both spatial dynamics and life history, but how these two factors interact is poorly understood. We conducted a longitudinal study of the wind-pollinated annual plant Mercurialis annua that varies geographically in its Sexual system to investigate this interaction. 2. Metapopulation demographic models predict that regular population turnover should be a more common feature of monomorphic than dimorphic populations because males and females cannot found new populations by selfing but hermaphrodites can. We tested the prediction that rates of population turnover would be higher in monomorphic compared to dimorphic regions. 3. We surveyed 356 populations of M. annua along five regional transects in Morocco and the Iberian Peninsula over a 3-year period to examine their demography and persistence. Each transect crossed a transition in the Sexual system, from a monomorphic region where almost all populations were hermaphroditic to a dimorphic one in which most populations had separate sexes (males with females or hermaphrodites). 4. As predicted, rates of local apparent extinctions (i.e., the disappearance of adult plants) were nearly 50% higher in monomorphic compared to dimorphic regions. Local extinctions appeared to be driven by changes in vegetation cover, with extinctions tending to occur in sites in which perennial cover also declined. This suggests that disturbance is a primary agent of local extinctions. 5. We further examined the influence of regional dynamics on local demographic properties by investigating patterns of spatial autocorrelation in population density across years. We found positive spatial autocorrelations in plant densities within regions for both Sexual Systems. However, these positive autocorrelations extended over shorter distances in monomorphic regions, perhaps as a result of greater population flux in these regions. 6. Synthesis. Our study shows that population dynamics may be influenced by processes acting at a range of spatial scales: within patches, across patches within sites, and across sites within regions, as well as by life-history variation. In Mercurialis annua, regional variation in apparent extinction rates is affected by life history and implicated in regulating the geographical distribution of populations with different Sexual Systems.
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Small‐scale and regional spatial dynamics of an annual plant with contrasting Sexual Systems
Journal of Ecology, 2017Co-Authors: Marcel E Dorken, Robert P Freckleton, John R PannellAbstract:1. Plant demography is known to depend on both spatial dynamics and life history, but how these two factors interact is poorly understood. We conducted a longitudinal study of the wind-pollinated annual plant Mercurialis annua that varies geographically in its Sexual system to investigate this interaction. 2. Metapopulation demographic models predict that regular population turnover should be a more common feature of monomorphic than dimorphic populations because males and females cannot found new populations by selfing but hermaphrodites can. We tested the prediction that rates of population turnover would be higher in monomorphic compared to dimorphic regions. 3. We surveyed 356 populations of M. annua along five regional transects in Morocco and the Iberian Peninsula over a 3-year period to examine their demography and persistence. Each transect crossed a transition in the Sexual system, from a monomorphic region where almost all populations were hermaphroditic to a dimorphic one in which most populations had separate sexes (males with females or hermaphrodites). 4. As predicted, rates of local apparent extinctions (i.e., the disappearance of adult plants) were nearly 50% higher in monomorphic compared to dimorphic regions. Local extinctions appeared to be driven by changes in vegetation cover, with extinctions tending to occur in sites in which perennial cover also declined. This suggests that disturbance is a primary agent of local extinctions. 5. We further examined the influence of regional dynamics on local demographic properties by investigating patterns of spatial autocorrelation in population density across years. We found positive spatial autocorrelations in plant densities within regions for both Sexual Systems. However, these positive autocorrelations extended over shorter distances in monomorphic regions, perhaps as a result of greater population flux in these regions. 6. Synthesis. Our study shows that population dynamics may be influenced by processes acting at a range of spatial scales: within patches, across patches within sites, and across sites within regions, as well as by life-history variation. In Mercurialis annua, regional variation in apparent extinction rates is affected by life history and implicated in regulating the geographical distribution of populations with different Sexual Systems.
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density dependent pollen limitation and reproductive assurance in a wind pollinated herb with contrasting Sexual Systems
Journal of Ecology, 2011Co-Authors: Elze Hesse, John R PannellAbstract:Summary 1. Wind pollination is thought to have evolved in response to selection for mechanisms to promote pollination success, when animal pollinators become scarce or unreliable. We might thus expect wind-pollinated plants to be less prone to pollen limitation than their insect-pollinated counterparts. Yet, if pollen loads on stigmas of wind-pollinated species decline with distance from pollen donors, seed set might nevertheless be pollen-limited in populations of plants that cannot self-fertilize their progeny, but not in self-compatible hermaphroditic populations. 2. Here, we test this hypothesis by comparing pollen limitation between dioecious and hermaphroditic (monoecious) populations of the wind-pollinated herb Mercurialis annua. 3. In natural populations, seed set was pollen-limited in low-density patches of dioecious, but not hermaphroditic, M. annua, a finding consistent with patterns of distance-dependent seed set by females in an experimental array. Nevertheless, seed set was incomplete in both dioecious and hermaphroditic populations, even at high local densities. Further, both factors limited the seed set of females and hermaphrodites, after we manipulated pollen and resource availability in a common garden experiment. 4. Synthesis. Our results are consistent with the idea that pollen limitation plays a role in the evolution of combined vs. separate sexes in M. annua. Taken together, they point to the potential importance of pollen transfer between flowers on the same plant (geitonogamy) by wind as a mechanism of reproductive assurance and to the dual roles played by pollen and resource availability in limiting seed set. Thus, seed set can be pollen-limited in sparse populations of a wind-pollinated species, where mates are rare or absent, having potentially important demographic and evolutionary implications.
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gender variation and transitions between Sexual Systems in mercurialis annua euphorbiaceae
International Journal of Plant Sciences, 2008Co-Authors: John R Pannell, Marcel E Dorken, Benoit Pujol, Regina BerjanoAbstract:Evolutionary transitions between hermaphroditism and dioecy have occurred numerous times in the land plants. We briefly review the factors thought to be responsible for these transitions, and we provide a synthesis of what has been learned from recent studies of the annual herb Mercurialis annua, in which dioecy (males and females), monoecy (functional hermaphrodites), and androdioecy (males and hermaphrodites) occur in different parts of its geographic range. Previous research on M. annua has revealed the importance of genome duplication and hybridization in the origin of much of the observed variation. Here we show, however, that spatial transitions in the Sexual system also occur within the same ploidy level. In particular, we present an analysis, using flow cytometry data, of ploidy variation across a previously unstudied transition between hermaphroditism and androdioecy, in which we find that the Sexual‐system transition is uncoupled from the shift in ploidy levels. We review recent research that sh...
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Sexual Systems and measures of occupancy and abundance in an annual plant testing the metapopulation model
The American Naturalist, 2007Co-Authors: Sarah M Eppley, John R PannellAbstract:Abstract: The need for reproductive assurance during dispersal, along with the pressure of local mate competition, means that the importance of frequent or repeated colonization is implicit in the Sexual‐system evolution literature. However, to date there have been few empirical tests of the association between colonization and the Sexual system in plants. Here we provide such a test by comparing occupancy and abundance of populations of the European plant Mercurialis annua across regions characterized by different Sexual Systems. Specifically, we predicted that monomorphic, hermaphroditic populations, which are thought to have evolved under selection for reproductive assurance during repeated bouts of colonization, would be smaller and their suitable habitat less frequently occupied than dimorphic populations, where males co‐occur with either females or hermaphrodites. We show that both of these predictions are upheld. We evaluate our results against competing hypotheses for the occupancy‐abundance relat...
Tialynn Ashman - One of the best experts on this subject based on the ideXlab platform.
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macroevolutionary synthesis of flowering plant Sexual Systems
Evolution, 2017Co-Authors: Emma E Goldberg, Itay Mayrose, Ray Ming, Sarah P Otto, Jana C Vamosi, Niv Sabath, Tialynn AshmanAbstract:Sexual system is a key determinant of genetic variation and reproductive success, affecting evolution within populations and within clades. Much research in plants has focused on evolutionary transitions away from the most common state of hermaphroditism and toward the rare state of dioecy (separate sexes). Rather than transitions predominantly toward greater Sexual differentiation, however, evolution may proceed in the direction of lesser Sexual differentiation. We analyzed the macroevolutionary dynamics of Sexual system in angiosperm genera that contain both dioecious and non-dioecious species. Our phylogenetic analyses encompass a total of 2145 species from 40 genera. Overall, we found little evidence that rates of Sexual system transitions are greater in any direction. Counting the number of inferred state changes revealed a mild prevalence of transitions away from hermaphroditism and away from dioecy, toward states of intermediate Sexual differentiation. We identify genera in which future studies of Sexual system evolution might be especially productive, and we discuss how integrating genetic or population-level studies of Sexual system could improve the power of phylogenetic comparative analyses. Our work adds to the evidence that different selective pressures and constraints act in different groups, helping maintain the variety of Sexual Systems observed among plants. This article is protected by copyright. All rights reserved
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Polyploidy and Sexual system in angiosperms: Is there an association?
American Journal of Botany, 2016Co-Authors: Lior Glick, Tialynn Ashman, Emma E Goldberg, Niv Sabath, Itay MayroseAbstract:PREMISE OF THE STUDY: Flowering plants display a variety of Sexual Systems, ranging from complete coSexuality (hermaphroditism) to separate-sexed individuals (dioecy). While dioecy is relatively rare, it has evolved many times and is present in many plant families. Transitions in Sexual Systems are hypothesized to be affected by large genomic events such as whole-genome duplication, or polyploidy, and several models have been proposed to explain the observed patterns of association. METHODS: In this study, we assessed the association between ploidy and Sexual system (separate or combined sexes). To this end, we assembled a database of ploidy levels and Sexual Systems for ∼1000 species, spanning 18 genera and 15 families. We applied several phylogenetic comparative approaches, including Pagel's coevolutionary framework and sister clade analyses, for detecting correlations between ploidy level and Sexual system. KEY RESULTS: Our results indicate a broad association between polyploidy and Sexual system dimorphism, with low evolutionary stability of the diploid-dioecious condition observed in several clades. A detailed examination of the clades exhibiting this correlation reveals that it is underlain by various patterns of transition rate asymmetry. CONCLUSIONS: We conclude that the long-hypothesized connection between ploidy and Sexual system holds in some clades, although it may well be affected by factors that differ from clade to clade. Our results further demonstrate that to better understand the evolutionary processes involved, more sophisticated methods and extensive and detailed data sets are required for both broad and focused inquiry.
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tree of sex a database of Sexual Systems
Scientific Data, 2014Co-Authors: Tialynn Ashman, Doris Bachtrog, Heath Blackmon, Emma E Goldberg, Matthew W Hahn, Mark Kirkpatrick, Jun Kitano, Judith E Mank, Itay Mayrose, Ray MingAbstract:The vast majority of eukaryotic organisms reproduce Sexually, yet the nature of the Sexual system and the mechanism of sex determination often vary remarkably, even among closely related species. Some species of animals and plants change sex across their lifespan, some contain hermaphrodites as well as males and females, some determine sex with highly differentiated chromosomes, while others determine sex according to their environment. Testing evolutionary hypotheses regarding the causes and consequences of this diversity requires interspecific data placed in a phylogenetic context. Such comparative studies have been hampered by the lack of accessible data listing Sexual Systems and sex determination mechanisms across the eukaryotic tree of life. Here, we describe a database developed to facilitate access to Sexual system and sex chromosome information, with data on Sexual Systems from 11,038 plant, 705 fish, 173 amphibian, 593 non-avian reptilian, 195 avian, 479 mammalian, and 11,556 invertebrate species.
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Quantitative character evolution under complicated Sexual Systems, illustrated in gynodioecious Fragaria virginiana.
The American Naturalist, 2003Co-Authors: Martin Morgan, Tialynn AshmanAbstract:Many taxa, especially plants, are famous for their diverse and complicated Sexual Systems. This diversity presents an obstacle to application of otherwise standard methods in evolutionary analysis. One example involves the quantitative genetics (Lande 1976, 1979; Lande and Arnold 1983) of phenotypic evolution. Standard methods of quantitative genetic analysis have been extended to and applied in separate sexed (Lande 1980; Meagher 1992, 1994; Ferguson and Fairbairn 2000) and hermaphroditic (Morgan 1992, 1994; Morgan and Schoen 1997) species, but quantitative genetic methods have not been developed to address other mating Systems such as androand gynodioecy; andro-, gyno-, and monoecy; or heterostyly. In this note, we develop Gaussian quantitative genetic approximations to describe how selection shapes traits expressed in females and hermaphrodites of a gynodioecious species where sex is under simple nuclear gene control. We then illustrate the approach through analysis of selection acting on petal size in Fragaria virginiana. Results of the empirical analysis suggest diverse ways in which Sexual Systems influence the evolution of quantitative characters. Finally, we give examples of how concepts used here (i.e., the inheritance of sex determination, fertility-weighted sex morph ratio, and
