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John R Pannell - One of the best experts on this subject based on the ideXlab platform.
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The rapid dissolution of Dioecy by experimental evolution.
Current biology : CB, 2021Co-Authors: Guillaume Cossard, Jörn Gerchen, Yves Cuenot, John R PannellAbstract:Evolutionary transitions from hermaphroditism to Dioecy have been common in flowering plants,1,2 but recent analysis also points to frequent reversions from Dioecy to hermaphroditism.2-4 Here, we use experimental evolution to expose a mechanism for such reversions, validating an explanation for the scattered phylogenetic distribution of Dioecy. We removed males from dioecious populations of the wind-pollinated plant Mercurialis annua and allowed natural selection to act on the remaining females that occasionally produced male flowers; such "leaky" sex expression is common in both males and females of dioecious plants.5 Over the course of four generations, females evolved a 23-fold increase in average male flower production. This phenotypic masculinization of females coincided with the evolution of partial self-fertilization, high average seed set in the continued absence of males, and a capacity to sire progeny when males were re-introduced into their populations. Our study thus validates a mechanism for the rapid dissolution of Dioecy and the evolution of functional hermaphroditism under conditions that may frequently occur during periods of low population density, repeated colonization, or range expansion.6,7 Our results illustrate the power of natural selection, acting in replicated experimental populations, to bring about transitions in the mating behavior of plants.
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Rapid dissolution of Dioecy by experimental evolution
2019Co-Authors: Guillaume Cossard, Jörn Gerchen, Yves Cuenot, John R PannellAbstract:Abstract Evolutionary transitions from hermaphroditism to Dioecy have been frequent in flowering plants, but recent analysis indicates that reversions from Dioecy to hermaphroditism have also been common. Here, we use experimental evolution to expose a mechanism for such reversions. We removed males from dioecious populations of the wind-pollinated plant Mercurialis annua and allowed natural selection to act on the remaining females that varied in their propensity for the occasional production of male flowers; such ‘leaky’ sex expression is common in both males and females of dioecious plants. Over only four generations, females evolved a 23-fold increase in average male-flower production. The phenotypic masculinization of females was also sufficient to render them effective at siring progeny in the presence of males. Our study illustrates the rapid dissolution of Dioecy and the evolution of functional hermaphroditism under conditions that may frequently occur during periods of low population density, repeated colonization, or range expansion. It thereby experimentally validates a mechanism for a major transition in plant sexual systems..
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A ghost of Dioecy past and the legacy of sexual dimorphism: low siring success of hermaphrodites after the breakdown of Dioecy
2018Co-Authors: Luis Santos-del-blanco, Eleri H Tudor, John R PannellAbstract:Evolutionary transitions from Dioecy to hermaphroditism must overcome the inertia of sexual dimorphism because modified males or females will express the opposite sexual function for which their phenotypes have been optimized. We tested this prediction by comparing the siring success of female-derived hermaphrodites of the plant Mercurialis annua with males and hermaphrodites that present a male-like inflorescence. We found that pollen dispersed by female-derived hermaphrodites was about a third poorer at siring outcross offspring than that from hermaphrodites with male-like inflorescences, illustrating the notion that a ghost of Dioecy past compromises the fitness of derived hermaphrodites in outcrossing populations. We conclude that whereas Dioecy might evolve from hermaphroditism by conferring upon individuals certain benefits of sexual specialization, reversals from Dioecy to hermaphroditism must often be limited to situations in which outcrossing cannot be maintained and inbreeding is favored. Our study provides novel empirical support for evolutionary models for the breakdown of Dioecy.
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On the rarity of Dioecy in flowering plants.
Molecular ecology, 2017Co-Authors: Jos Käfer, Gabriel A. B. Marais, John R PannellAbstract:Dioecy, the coexistence of separate male and female individuals in a population, is a rare but phylogenetically widespread sexual system in flowering plants. While research has concentrated on why and how Dioecy evolves from hermaphroditism, the question of why Dioecy is rare, despite repeated transitions to it, has received much less attention. Previous phylogenetic and theoretical studies have suggested that Dioecy might be an evolutionary dead end. However, recent research indicates that the phylogenetic support for this hypothesis is attributable to a methodological bias and that there is no evidence for reduced diversification in dioecious angiosperms. The relative rarity of Dioecy thus remains a puzzle. Here, we review evidence for the hypothesis that Dioecy might be rare not because it is an evolutionary dead end, but rather because it easily reverts to hermaphroditism. We review what is known about transitions between hermaphroditism and Dioecy, and conclude that there is an important need to consider more widely the possibility of transitions away from Dioecy, both from an empirical and a theoretical point of view, and by combining tools from molecular evolution and insights from ecology.
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sexual systems and population genetic structure in an annual plant testing the metapopulation model
The American Naturalist, 2006Co-Authors: Darren J Obbard, Stephen A Harris, 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 literature on sexual system evolution. However, there have been few empirical tests of the association between colonization history and sexual system in plants, and none within a single species. Here we use patterns of genetic diversity to provide such a test in the Mercurialis annua species complex, which spans the range of systems from self‐compatible monoecy through androDioecy to Dioecy. This variation has been hypothesized to result from differing patterns of metapopulation turnover and recolonization. Because monoecy should be favored during colonization, androDioecy and Dioecy will be maintained only in regions with low rates of local extinction and recolonization, and these differences should also be reflected in patterns of neutral genetic diversity. We show that monoecious populations of M. annua displ...
Susanne S Renner - One of the best experts on this subject based on the ideXlab platform.
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Plant sex chromosomes defy evolutionary models of expanding recombination suppression and genetic degeneration
Nature Plants, 2021Co-Authors: Susanne S Renner, Niels A. MüllerAbstract:Hundreds of land plant lineages have independently evolved separate sexes in either gametophytes (dioicy) or sporophytes (Dioecy), but 43% of all dioecious angiosperms are found in just 34 entirely dioecious clades, suggesting that their mode of sex determination evolved a long time ago. Here, we review recent insights on the molecular mechanisms that underlie the evolutionary change from individuals that each produce male and female gametes to individuals specializing in the production of just one type of gamete. The canonical model of sex chromosome evolution in plants predicts that two sex-determining genes will become linked in a sex-determining region (SDR), followed by expanding recombination suppression, chromosome differentiation and, ultimately, degeneration. Experimental work, however, is showing that single genes function as master regulators in model systems, such as the liverwort Marchantia and the angiosperms Diospyros and Populus . In Populus , this type of regulatory function has been demonstrated by genome editing. In other systems, including Actinidia , Asparagus and Vitis , two coinherited factors appear to independently regulate female and male function, yet sex chromosome differentiation has remained low. We discuss the best-understood systems and evolutionary pathways to Dioecy, and present a meta-analysis of the sizes and ages of SDRs. We propose that limited sexual conflict explains why most SDRs are small and sex chromosomes remain homomorphic. It appears that models of increasing recombination suppression with age do not apply because selection favours mechanisms in which sex determination depends on minimal differences, keeping it surgically precise. This work reviews our understanding of plant sex-determining systems and the molecular mechanisms underlying the evolutionary shifts to Dioecy. The homomorphy of plant sex chromosomes and their small sex-determining regions are attributed to limited sexual conflict.
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the relative and absolute frequencies of angiosperm sexual systems Dioecy monoecy gynoDioecy and an updated online database
American Journal of Botany, 2014Co-Authors: Susanne S RennerAbstract:UNLABELLED: • PREMISE OF THE STUDY: Separating sexual function between different individuals carries risks, especially for sedentary organisms. Nevertheless, many land plants have unisexual gametophytes or sporophytes. This study brings together data and theoretical insights from research over the past 20 yr on the occurrence and frequency of plant sexual systems, focusing on the flowering plants.• METHODS: A list of genera with dioecious species, along with other information, is made available (http://www.umsl.edu/∼renners/). Frequencies of other sexual systems are tabulated, and data on the genetic regulation, ecological context, and theoretical benefits of Dioecy reviewed.• KEY RESULTS: There are 15600 dioecious angiosperms in 987 genera and 175 families, or 5-6% of the total species (7% of genera, 43% of families), with somewhere between 871 to 5000 independent origins of Dioecy. Some 43% of all dioecious angiosperms are in just 34 entirely dioecious clades, arguing against a consistent negative influence of Dioecy on diversification. About 31.6% of the dioecious species are wind-pollinated, compared with 5.5-6.4% of nondioecious angiosperms. Also, 1.4% of all angiosperm genera contain dioecious and monoecious species, while 0.4% contain dioecious and gynodioecious species. All remaining angiosperm sexual systems are rare. Chromosomal sex determination is known from 40 species; environmentally modulated sex allocation is common. Few phylogenetic studies have focused on the evolution of Dioecy.• CONCLUSIONS: The current focus is on the genetic mechanisms underlying unisexual flowers and individuals. Mixed strategies of sexual and vegetative dispersal, together with plants' sedentary life style, may often favor polygamous systems in which sexually inconstant individuals can persist. Nevertheless, there are huge entirely dioecious clades of tropical woody plants.
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the evolution of Dioecy heterodichogamy and labile sex expression in acer
Evolution, 2007Co-Authors: Susanne S Renner, Liese Beenken, Guido W Grimm, Alexander Kocyan, Robert E RicklefsAbstract:The northern hemisphere tree genus Acer comprises 124 species, most of them monoecious, but 13 dioecious. The monoecious species flower dichogamously, duodichogamously (male, female, male), or in some species heterodichogamously (two morphs that each produce male and female flowers but at reciprocal times). Dioecious species cannot engage in these temporal strategies. Using a phylogeny for 66 species and subspecies obtained from 6600 nucleotides of chloroplast introns, spacers, and a protein-coding gene, we address the hypothesis (Pannell and Verdu, Evolution 60: 660–673. 2006) that Dioecy evolved from heterodichogamy. This hypothesis was based on phylogenetic analyses (Gleiser and Verdu, New Phytol. 165: 633–640. 2005) that included 29–39 species of Acer coded for five sexual strategies (duodichogamous monoecy, heterodichogamous androDioecy, heterodichogamous trioecy, dichogamous subDioecy, and Dioecy) treated as ordered states or as a single continuous variable. When reviewing the basis for these scorings, we found errors that together with the small taxon sample, cast doubt on the earlier inferences. Based on published studies, we coded 56 species of Acer for four sexual strategies, Dioecy, monoecy with dichogamous or duodichogamous flowering, monoecy with heterodichogamous flowering, or labile sex expression, in which individuals reverse their sex allocation depending on environment–phenotype interactions. Using Bayesian character mapping, we infer an average of 15 transformations, a third of them involving changes from monoecy-cum-duodichogamy to Dioecy; less frequent were changes from this strategy to heterodichogamy; Dioecy rarely reverts to other sexual systems. Contra the earlier inferences, we found no switches between heterodichogamy and Dioecy. Unexpectedly, most of the species with labile sex expression are grouped together, suggesting that phenotypic plasticity in Acer may be a heritable sexual strategy. Because of the complex flowering phenologies, however, a concern remains that monoecy in Acer might not always be distinguishable from labile sex expression, which needs to be addressed by long-term monitoring of monoecious trees. The 13 dioecious species occur in phylogenetically disparate clades that date back to the Late Eocene and Oligocene, judging from a fossil-calibrated relaxed molecular clock.
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Repeated Evolution of Dioecy from Monoecy in Siparunaceae (Laurales)
Systematic biology, 2001Co-Authors: Susanne S Renner, Hyosig WonAbstract:Siparunaceae comprise Glossocalyx with one species in West Africa and Siparuna with 65 species in the neotropics; all have unisexual flowers, and 15 species are monoecious, 50 dioecious. Parsimony and maximum likelihood analyses of combined nuclear ribosomal ITS and chloroplast trnL-trnF intergenic spacer sequences yielded almost identical topologies, which were used to trace the evolution of the two sexual systems. The African species, which is dioecious, was sister to all neotropical species, and the monoecious species formed a grade basal to a large dioecious Andean clade. Dioecy evolved a second time within the monoecious grade. Geographical mapping of 6,496 herbarium collections from all species sorted by sexual system showed that monoecy is confined to low-lying areas (altitude < 700 m) in the Amazon basin and southern Central America. The only morphological trait with a strong phylogenetic signal is leaf margin shape (entire or toothed), although this character also correlates with altitude, probably reflecting selection on leaf shapes by temperature and rainfall regimes. The data do not reject the molecular clock, and branch lengths suggest that the shift to Dioecy in the lowlands occurred many million years after the shift to Dioecy in the ancestor of the Andean clade.
Mathilde Dufay - One of the best experts on this subject based on the ideXlab platform.
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polygamy or subDioecy the impact of diallelic self incompatibility on the sexual system in fraxinus excelsior oleaceae
Proceedings of The Royal Society B: Biological Sciences, 2018Co-Authors: Pierre Saumitoulaprade, Mathilde Dufay, Pierre-henri Gouyon, Philippe Vernet, Arnaud Dowkiw, Sylvain Bertrand, Sylvain Billiard, Beatrice AlbertAbstract:How flowering plants have recurrently evolved from hermaphroditism to separate sexes (Dioecy) is a central question in evolutionary biology. Here, we investigate whether diallelic self-incompatibility (DSI) is associated with sexual specialization in the polygamous common ash ( Fraxinus excelsior ), which would ultimately facilitate the evolution towards Dioecy. Using interspecific crosses, we provide evidence of strong relationships between the DSI system and sexual phenotype. The reproductive system in F. excelsior that was previously viewed as polygamy (co-occurrence of unisexuals and hermaphrodites with varying degrees of allocation to the male and female functions) and thus appears to actually behave as a subdioecious system. Hermaphrodites and females belong to one SI group and functionally reproduce as females, whereas males and male-biased hermaphrodites belong to the other SI group and are functionally males. Our results offer an alternative mechanism for the evolution of sexual specialization in flowering plants.
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Sexual phenotype, incompatibility groups and intensity of fruiting of the F. excelsior trees originating from the Cevennes National Park (southern France) from Polygamy or subDioecy? The impact of diallelic self-incompatibility on the sexual system i
2018Co-Authors: Pierre Saumitou-laprade, Pierre-henri Gouyon, Philippe Vernet, Arnaud Dowkiw, Sylvain Bertrand, Sylvain Billiard, Beatrice Albert, Mathilde DufayAbstract:How flowering plants have recurrently evolved from hermaphroditism to separate sexes (Dioecy) is a central question in evolutionary biology. Here, we investigate whether diallelic self-incompatibility (DSI) is associated with sexual specialization in the polygamous common ash (Fraxinus excelsior), which would ultimately facilitate the evolution towards Dioecy. Using interspecific crosses, we provide evidence of strong relationships between the DSI system and sexual phenotype. The reproductive system in F. excelsior that was previously viewed as polygamy (co-occurrence of unisexuals and hermaphrodites with varying degrees of allocation to the male and female functions) thus appears to actually behave as a subdioecious system. Hermaphrodites and females belong to one SI group and functionally reproduce as females, whereas males and male-biased hermaphrodites belong to the other SI group and are functionally males. Our results offer an alternative mechanism for the evolution of sexual specialization in flowering plants
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Distribution of fruit production according to sexual phenotypic value of Fraxinus excelsior individuals in two populations from Polygamy or subDioecy? The impact of diallelic self-incompatibility on the sexual system in Fraxinus excelsior (Oleaceae)
2018Co-Authors: Pierre Saumitou-laprade, Pierre-henri Gouyon, Philippe Vernet, Arnaud Dowkiw, Sylvain Bertrand, Sylvain Billiard, Beatrice Albert, Mathilde DufayAbstract:How flowering plants have recurrently evolved from hermaphroditism to separate sexes (Dioecy) is a central question in evolutionary biology. Here, we investigate whether diallelic self-incompatibility (DSI) is associated with sexual specialization in the polygamous common ash (Fraxinus excelsior), which would ultimately facilitate the evolution towards Dioecy. Using interspecific crosses, we provide evidence of strong relationships between the DSI system and sexual phenotype. The reproductive system in F. excelsior that was previously viewed as polygamy (co-occurrence of unisexuals and hermaphrodites with varying degrees of allocation to the male and female functions) thus appears to actually behave as a subdioecious system. Hermaphrodites and females belong to one SI group and functionally reproduce as females, whereas males and male-biased hermaphrodites belong to the other SI group and are functionally males. Our results offer an alternative mechanism for the evolution of sexual specialization in flowering plants
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Sexual phenotypic values, SI phenotype, and estimate of fruit production of the F. excelsior individual genotypes originating from Normandy (France) from Polygamy or subDioecy? The impact of diallelic self-incompatibility on the sexual system in Frax
2018Co-Authors: Pierre Saumitou-laprade, Pierre-henri Gouyon, Philippe Vernet, Arnaud Dowkiw, Sylvain Bertrand, Sylvain Billiard, Beatrice Albert, Mathilde DufayAbstract:How flowering plants have recurrently evolved from hermaphroditism to separate sexes (Dioecy) is a central question in evolutionary biology. Here, we investigate whether diallelic self-incompatibility (DSI) is associated with sexual specialization in the polygamous common ash (Fraxinus excelsior), which would ultimately facilitate the evolution towards Dioecy. Using interspecific crosses, we provide evidence of strong relationships between the DSI system and sexual phenotype. The reproductive system in F. excelsior that was previously viewed as polygamy (co-occurrence of unisexuals and hermaphrodites with varying degrees of allocation to the male and female functions) thus appears to actually behave as a subdioecious system. Hermaphrodites and females belong to one SI group and functionally reproduce as females, whereas males and male-biased hermaphrodites belong to the other SI group and are functionally males. Our results offer an alternative mechanism for the evolution of sexual specialization in flowering plants
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Dioecy is associated with higher diversification rates in flowering plants
Journal of evolutionary biology, 2014Co-Authors: Jos Käfer, H. J. De Boer, Sylvain Mousset, Anneleen Kool, Mathilde Dufay, Gabriel A. B. MaraisAbstract:In angiosperms, dioecious clades tend to have fewer species than their nondioecious sister clades. This departure from the expected equal species richness in the standard sister clade test has been interpreted as implying that dioecious clades diversify less and has initiated a series of studies suggesting that Dioecy might be an 'evolutionary dead end'. However, two of us recently showed that the 'equal species richness' null hypothesis is not valid in the case of derived char acters, such as Dioecy, and proposed a new test for sister clade comparisons; preliminary results, using a data set available in the litterature, indicated that dioecious clades migth diversify more than expected. However, it is crucial for this new test to distinguish between ancestral and derived cases of Dioecy, a criterion that was not taken into account in the available data set. Here, we present a new data set that was obtained by searching the phylogenetic literature on more than 600 completely dioecious angiosperm genera and identifying 115 sister clade pairs for which Dioecy is likely to be derived (including > 50% of the dioecious species). Applying the new sister clade test to this new dataset, we confirm the preliminary result that Dioecy is associated with an increased diversification rate, a result that does not support the idea that Dioecy is an evolutionary dead end in angiosperms. The traits usually associated with Dioecy, that is, an arborescent growth form, abiotic pollination, fleshy fruits or a tropical distribution, do not influence the diversification rate. Rather than a low diversification rate, the observed species richness patterns of dioecious clades seem to be better explained by a low transition rate to Dioecy and frequent losses.
Gregory J. Anderson - One of the best experts on this subject based on the ideXlab platform.
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The ecology, evolution, and biogeography of Dioecy in the genus Solanum: With paradigms from the strong Dioecy in Solanum polygamum, to the unsuspected and cryptic Dioecy in Solanum conocarpum
American journal of botany, 2015Co-Authors: Gregory J. Anderson, Mona K. J. Anderson, Nikisha PatelAbstract:UNLABELLED • PREMISE OF THE STUDY Island plants are over-exploited and "under-explored." Understanding the reproductive biology of plants, especially rare species, is fundamental to clarifying their evolution, estimating potential for change, and for creating effective conservation plans. Clarification of sexual systems like Dioecy, and unusual manifestations of it in specific studies within Solanum, helps elucidate evolutionary patterns and genetic and ecological control of sex expression.• METHODS Studies of reproductive systems of two Caribbean endemics, S. polygamum and S. conocarpum, combined multifaceted analyses of field populations and of multiple generations of greenhouse plants.• KEY RESULTS The Dioecy in both species is, like that in other solanums, largely cryptic, although the gender of S. polygamum flowers is obvious. The rare S. conocarpum is recognized as dioecious; floral gender is not obvious. Variation in sex expression facilitated experiments and promoted hypotheses on control and significance of morphological features and sex expression.• CONCLUSIONS Confirmed Dioecy in at least 15 solanums is distributed across the genus, with perhaps 6 independent origins, and with crypticity in the form of morphologically hermaphroditic, but functionally unisexual, flowers characterizing all species. Dioecy is not more strongly associated with islands. Inaperturate pollen in pistillate flowers characterizes almost all, but not the two dioecious species studied herein. Dioecy in both species indicates leakiness (rare hermaphroditic flowers on male plants) that helps explain island colonization and radiation. Leakiness allowed confirmation-usually impossible for dioecious species-of self-compatibility for S. polygamum, and thus support for the hypothesis that Dioecy evolved to promote outcrossing.
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Dioecy in South American Deprea (Solanaceae)1
BIOTROPICA, 2000Co-Authors: Neil W. Sawyer, Gregory J. AndersonAbstract:Abstract Dioecy in the Solanaceae is rare, occurring in
Deborah Charlesworth - One of the best experts on this subject based on the ideXlab platform.
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Multiple nuclear gene phylogenetic analysis of the evolution of Dioecy and sex chromosomes in the genus Silene.
PloS one, 2011Co-Authors: Gabriel A. B. Marais, Jos Käfer, Alan Forrest, Esther Kamau, Vincent Daubin, Deborah CharlesworthAbstract:In the plant genus Silene, separate sexes and sex chromosomes are believed to have evolved twice. Silene species that are wholly or largely hermaphroditic are assumed to represent the ancestral state from which Dioecy evolved. This assumption is important for choice of outgroup species for inferring the genetic and chromosomal changes involved in the evolution of Dioecy, but is mainly based on data from a single locus (ITS). To establish the order of events more clearly, and inform outgroup choice, we therefore carried out (i) multi-nuclear-gene phylogenetic analyses of 14 Silene species (including 7 hermaphrodite or gynodioecious species), representing species from both Silene clades with dioecious members, plus a more distantly related outgroup, and (ii) a BayesTraits character analysis of the evolution of Dioecy. We confirm two origins of Dioecy within this genus in agreement with recent work on comparing sex chromosomes from both clades with dioecious species. We conclude that sex chromosomes evolved after the origin of Silene and within a clade that includes only S. latifolia and its closest relatives. We estimate that sex chromosomes emerged soon after the split with the ancestor of S. viscosa, the probable closest non-dioecious S. latifolia relative among the species included in our study.
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genetic evidence for multiple origins of Dioecy in the hawaiian shrub wikstroemia thymelaeaceae
Evolution, 1992Co-Authors: Stephanie S Mayer, Deborah CharlesworthAbstract:Dioecy is unusually common in the Hawaiian Islands, yet little is known about the evolutionary biology of this breeding system. A native shrub, Wikstroemia, has an unusually diverse array of breeding systems: two forms of Dioecy, cryptic and morphological Dioecy, as well as hermaphroditism (perfect flowers). The existence of two forms of Dioecy is significant for three reasons: 1) the presence of cryptic unisexuals that are functionally unisexual, but retain the appearance of hermaphroditism in both sexes, is strong evidence for the ancestral status of hermaphroditism; 2) the production of nonfunctional pollen, by female cryptic unisexuals, is a new instance of a phenomenon which has previously been reported for a few other species; 3) the two forms of Dioecy are morphological markers which are useful in hybridization studies for tracing the genetic basis of their inheritance. Crosses were made between cryptically unisexual individuals (C), between morphologically unisexual individuals (M), and between the two types of unisexuality. The offspring of crosses between individuals with the same sex type usually resulted in offspring with that sex type, but most of the progeny of between-sex type crosses were, unexpectedly, perfect-flowered hermaphrodites. These results show that genetic control of sex determination is not homologous in all populations, suggesting that Dioecy has evolved at least twice in Hawaiian Wikstroemia. The genetic data further suggest that males are the heterozygous sex.
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Cryptic Dioecy in flowering plants
Trends in ecology & evolution, 1991Co-Authors: S.s. Mayer, Deborah CharlesworthAbstract:In some dioecious plant species, mates and/or females have large and presumably costly opposite-sex structures that are sterile. This is termed 'cryptic Dioecy'. Several new cases of cryptic Dioecy have recently been studied. They may give information about the minimal requirements for the evolution of separate sexes from hermaphroditism, because the most important differences contributing to the initial advantage of the breeding system have not been obscured by further developments. Reviewed in this light, cryptic Dioecy can provide evidence on the role of reallocation of reproductive resources in the evolution of Dioecy.