The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Spencer C H Barrett - One of the best experts on this subject based on the ideXlab platform.
-
the consequences of Monoecy and protogyny for mating in wind pollinated carex
New Phytologist, 2009Co-Authors: Jannice Friedman, Spencer C H BarrettAbstract:Summary • Monoecy and protogyny are widespread in wind-pollinated plants and have been interpreted as outcrossing mechanisms, though few studies have investigated their function. Carex, a large genus of anemophilous herbs, is predominantly monoecious and many species are protogynous. We investigated whether Monoecy and protogyny limit self-pollination in seven Carex species. • We conducted field experiments comparing stigmatic pollen loads and seed set between intact and emasculated stems. We tested for self-compatibility and evaluated pollen limitation of seed set by supplemental pollination. Finally, we measured outcrossing rates in open-pollinated and emasculated stems using allozyme markers. • Emasculated stems captured significantly less pollen than open-pollinated stems and set less seed. Pollen deposition during the female-only phase for intact stems was only 12% of the total captured. Outcrossing rates for three species indicated high selfing (range t = 0.03–0.39). Allozyme loci in the remaining species were monomorphic also suggesting high selfing. These results demonstrate that neither Monoecy nor protogyny is particularly effective at limiting self-fertilization. • Selection for the avoidance of selfing is unlikely to maintain Monoecy in many Carex species although protogyny may provide limited opportunities for outcrossing. We propose that geitonogamy in self-compatible wind-pollinated species with unisexual flowers may be widespread and provides reproductive assurance.
-
The consequences of Monoecy and protogyny for mating in wind‐pollinated Carex
The New phytologist, 2008Co-Authors: Jannice Friedman, Spencer C H BarrettAbstract:Summary • Monoecy and protogyny are widespread in wind-pollinated plants and have been interpreted as outcrossing mechanisms, though few studies have investigated their function. Carex, a large genus of anemophilous herbs, is predominantly monoecious and many species are protogynous. We investigated whether Monoecy and protogyny limit self-pollination in seven Carex species. • We conducted field experiments comparing stigmatic pollen loads and seed set between intact and emasculated stems. We tested for self-compatibility and evaluated pollen limitation of seed set by supplemental pollination. Finally, we measured outcrossing rates in open-pollinated and emasculated stems using allozyme markers. • Emasculated stems captured significantly less pollen than open-pollinated stems and set less seed. Pollen deposition during the female-only phase for intact stems was only 12% of the total captured. Outcrossing rates for three species indicated high selfing (range t = 0.03–0.39). Allozyme loci in the remaining species were monomorphic also suggesting high selfing. These results demonstrate that neither Monoecy nor protogyny is particularly effective at limiting self-fertilization. • Selection for the avoidance of selfing is unlikely to maintain Monoecy in many Carex species although protogyny may provide limited opportunities for outcrossing. We propose that geitonogamy in self-compatible wind-pollinated species with unisexual flowers may be widespread and provides reproductive assurance.
-
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 .
-
sex determination and the evolution of dioecy from Monoecy in sagittaria latifolia alismataceae
Proceedings of The Royal Society B: Biological Sciences, 2004Co-Authors: Marcel E Dorken, Spencer C H BarrettAbstract:The role of mutations of small versus large effect in adaptive evolution is of considerable interest to evolutionary biologists. The major evolutionary pathways for the origin of dioecy in plants (the gynodioecy and Monoecy-paradioecy pathways) are often distinguished by the number of mutations involved and the magnitude of their effects. Here, we investigate the genetic and environmental determinants of sex in Sagittaria latifolia, a species with both monoecious and dioecious populations, and evaluate evidence for the evolution of dioecy via gynodioecy or Monoecy-paradioecy. We crossed plants of the two sexual systems to generate F1, F2 and backcross progeny, and grew clones from dioecious populations in low-and high-fertilizer conditions to examine sex inconstancy in females and males. Several lines of evidence implicate two-locus control of the sex phenotypes. In dioecious populations sex is determined by Mendelian segregation of alleles, with males heterozygous at both the male- and female-sterility loci. In monoecious populations, plants are homozygous for alleles dominant to male sterility in females and recessive to female sterility in males. Experimental manipulation of resources revealed sex inconstancy in males but not females. These results are consistent with predictions for the evolution of dioecy via gynodioecy, rather than the expected Monoecy-paradioecy pathway, given the ancestral monoecious condition.
-
life history differentiation and the maintenance of Monoecy and dioecy in sagittaria latifolia alismataceae
Evolution, 2003Co-Authors: Marcel E Dorken, Spencer C H BarrettAbstract:The existence of monoecious and dioecious populations within plant species is rare. This limits opportunities to investigate the ecological mechanisms responsible for the evolution and maintenance of these contrasting sexual systems. In Sagittaria latifolia, an aquatic flowering plant, monoecious and dioecious populations exist in close geographic proximity but occupy distinct wetland habitats differing in the relative importance of disturbance and competition, respectively. Life-history theory predicts contrasting evolutionary responses to these environmental conditions. We propose that the maintenance of Monoecy and dioecy in S. latifolia is governed by ecological selection of divergent life-history strategies in contrasting habitats. Here we evaluate this hypothesis by comparing components of growth and reproduction between monoecious and dioecious populations under four conditions: natural populations, a uniform glasshouse environment, a common garden in which monoecious and dioecious populations and their F1 progeny were compared, and a transplant experiment using shaded and unshaded plots in a freshwater marsh. Plants from dioecious populations were larger in size and produced heavier corms in comparison with monoecious populations. Monoecious populations flowered earlier and produced more flowers, clonal ramets, and corms than dioecious populations. The life-history differences between the sexual systems were shown to have a quantitative genetic basis, with F1 progeny generally exhibiting intermediate trait values. Survival was highest for each sexual system in field plots that most closely resembled the habitats in which monoecious (unshaded) and dioecious (shaded) populations grow. These results demonstrate that monoecious and dioecious populations exhibit contrasting patterns of investment in traits involved with growth and reproduction. Selection for divergent life histories between monoecious and dioecious populations of S. latifolia appears to be the principal mechanism maintaining the integrity of the two sexual systems in areas of geographic overlap.
Marcel E Dorken - One of the best experts on this subject based on the ideXlab platform.
-
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 .
-
sex determination and the evolution of dioecy from Monoecy in sagittaria latifolia alismataceae
Proceedings of The Royal Society B: Biological Sciences, 2004Co-Authors: Marcel E Dorken, Spencer C H BarrettAbstract:The role of mutations of small versus large effect in adaptive evolution is of considerable interest to evolutionary biologists. The major evolutionary pathways for the origin of dioecy in plants (the gynodioecy and Monoecy-paradioecy pathways) are often distinguished by the number of mutations involved and the magnitude of their effects. Here, we investigate the genetic and environmental determinants of sex in Sagittaria latifolia, a species with both monoecious and dioecious populations, and evaluate evidence for the evolution of dioecy via gynodioecy or Monoecy-paradioecy. We crossed plants of the two sexual systems to generate F1, F2 and backcross progeny, and grew clones from dioecious populations in low-and high-fertilizer conditions to examine sex inconstancy in females and males. Several lines of evidence implicate two-locus control of the sex phenotypes. In dioecious populations sex is determined by Mendelian segregation of alleles, with males heterozygous at both the male- and female-sterility loci. In monoecious populations, plants are homozygous for alleles dominant to male sterility in females and recessive to female sterility in males. Experimental manipulation of resources revealed sex inconstancy in males but not females. These results are consistent with predictions for the evolution of dioecy via gynodioecy, rather than the expected Monoecy-paradioecy pathway, given the ancestral monoecious condition.
-
life history differentiation and the maintenance of Monoecy and dioecy in sagittaria latifolia alismataceae
Evolution, 2003Co-Authors: Marcel E Dorken, Spencer C H BarrettAbstract:The existence of monoecious and dioecious populations within plant species is rare. This limits opportunities to investigate the ecological mechanisms responsible for the evolution and maintenance of these contrasting sexual systems. In Sagittaria latifolia, an aquatic flowering plant, monoecious and dioecious populations exist in close geographic proximity but occupy distinct wetland habitats differing in the relative importance of disturbance and competition, respectively. Life-history theory predicts contrasting evolutionary responses to these environmental conditions. We propose that the maintenance of Monoecy and dioecy in S. latifolia is governed by ecological selection of divergent life-history strategies in contrasting habitats. Here we evaluate this hypothesis by comparing components of growth and reproduction between monoecious and dioecious populations under four conditions: natural populations, a uniform glasshouse environment, a common garden in which monoecious and dioecious populations and their F1 progeny were compared, and a transplant experiment using shaded and unshaded plots in a freshwater marsh. Plants from dioecious populations were larger in size and produced heavier corms in comparison with monoecious populations. Monoecious populations flowered earlier and produced more flowers, clonal ramets, and corms than dioecious populations. The life-history differences between the sexual systems were shown to have a quantitative genetic basis, with F1 progeny generally exhibiting intermediate trait values. Survival was highest for each sexual system in field plots that most closely resembled the habitats in which monoecious (unshaded) and dioecious (shaded) populations grow. These results demonstrate that monoecious and dioecious populations exhibit contrasting patterns of investment in traits involved with growth and reproduction. Selection for divergent life histories between monoecious and dioecious populations of S. latifolia appears to be the principal mechanism maintaining the integrity of the two sexual systems in areas of geographic overlap.
-
the evolution and maintenance of Monoecy and dioecy in sagittaria latifolia alismataceae
Evolution, 2002Co-Authors: Marcel E Dorken, Jannice Friedman, Spencer C H BarrettAbstract:Abstract Plant species rarely exhibit both monoecious and dioecious sexual systems. This limits opportunities to investigate the consequences of combined versus separate sex function on mating patterns and genetic variation and the analysis of factors responsible for the evolution and maintenance of the two sexual systems. Populations of the North American clonal aquatic Sagittaria latifolia are usually either monoecious or dioecious and often grow in close geographic proximity. We investigated mating patterns, genetic structure, and relationships between the two sexual systems using allozyme variation in populations from southern Ontario, Canada. As predicted, selfing rates in monoecious populations (n = 6, mean = 0.41) were significantly higher than in dioecious populations (n = 6, mean = 0.11). Moreover, marker-based estimates of inbreeding depression (δ) indicated strong selection against inbred offspring in both monoecious (mean δ = 0.83) and dioecious (mean δ = 0.84) populations. However, the differ...
-
the evolution and maintenance of Monoecy and dioecy in sagittaria latifolia alismataceae
Evolution, 2002Co-Authors: Marcel E Dorken, Jannice Friedman, Spencer C H BarrettAbstract:Plant species rarely exhibit both monoecious and dioecious sexual systems. This limits opportunities to investigate the consequences of combined versus separate sex function on mating patterns and genetic variation and the analysis of factors responsible for the evolution and maintenance of the two sexual systems. Populations of the North American clonal aquatic Sagittaria latifolia are usually either monoecious or dioecious and often grow in close geographic proximity. We investigated mating patterns, genetic structure, and relationships between the two sexual systems using allozyme variation in populations from southern Ontario, Canada. As predicted, selfing rates in monoecious populations (n = 6, mean = 0.41) were significantly higher than in dioecious populations (n = 6, mean = 0.11). Moreover, marker-based estimates of inbreeding depression (delta) indicated strong selection against inbred offspring in both monoecious (mean delta = 0.83) and dioecious (mean delta = 0.84) populations. However, the difference in selfing rate between the sexual systems was not reflected in contrasting levels of genetic variation. Our surveys of 12 loci in 15 monoecious and 11 dioecious populations revealed no significant differences in the proportion of polymorphic loci (P), number of alleles per locus (A), or observed and expected heterozygosity (H(o) and H(e), respectively). Strong inbreeding depression favoring survival of outcrossed offspring may act to maintain similar levels of diversity between monoecious and dioecious populations. Despite geographical overlap between the two sexual systems in southern Ontario, a dendrogram of genetic relationships indicated two distinct clusters of populations largely corresponding to monoecious and dioecious populations. Reproductive isolation between monoecious and dioecious populations appears to be governed, in part, by observed differences in habitat and life history. We suggest that selfing and inbreeding depression in monoecious populations are important in the transition from Monoecy to dioecy and that the maintenance of distinct sexual systems in S. latifolia is governed by interactions between ecology, life history, and mating.
Susanne S Renner - One of the best experts on this subject based on the ideXlab platform.
-
Repeated evolution of dioecy from Monoecy in Siparunaceae (Laurales). Systematic Biology 50: 700–712
2015Co-Authors: Susanne S Renner, Hyosig WonAbstract:Abstract.—Siparunaceae comprise Glossocalyx with one species in West Africa and Siparuna with 65 species in the neotropics; all have unisexual owers, 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 conned to low-lying areas (altitude< 700m) in the Amazon basin and southern Central America. The onlymor-phological trait with a strong phylogenetic signal is leaf margin shape (entire or toothed), although this character also correlates with altitude, probably reecting 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. [Altitudinal distribution of sexual systems; dioecy; molecular clock; Monoecy; sexual system evolution.
-
Repeated Evolution of Dioecy from Monoecy in Siparunaceae (Laurales)
2014Co-Authors: Susanne S Renner, Hyosig WonAbstract:Abstract.—Siparunaceae comprise Glossocalyx with one species in West Africa and Siparuna with 65 species in the neotropics; all have unisexual owers, 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 conned to low-lying areas (altitude < 700m) in the Amazon basin and southern Central America. The only mor-phological trait with a strong phylogenetic signal is leaf margin shape (entire or toothed), although this character also correlates with altitude, probably reecting 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. [Altitudinal distribution of sexual systems; dioecy; molecular clock; Monoecy; sexual system evolution.
-
Correlates of monoicy and dioicy in hornworts, the apparent sister group to vascular plants
BMC Evolutionary Biology, 2013Co-Authors: Juan Carlos Villarreal, Susanne S RennerAbstract:Background Whether male and female gametes are produced by single or separate individuals shapes plant mating and hence patterns of genetic diversity among and within populations. Haploid-dominant plants (“bryophytes”: liverworts, mosses and hornworts) can have unisexual (dioicous) or bisexual (monoicous) gametophytes, and today, 68% of liverwort species, 57% of moss species, and 40% of hornwort species are dioicous. The transitions between the two sexual systems and possible correlations with other traits have been studied in liverworts and mosses, but not hornworts. Here we use a phylogeny for 98 of the 200 species of hornworts, the sister group to vascular plants, representing roughly equal proportions of all monoicous and all dioicous species, to test whether transitions in sexual systems are predominantly from monoicy to dioicy as might be expected based on studies of mosses. We further investigate possible correlations between sexual system and spore size, antheridium number, ploidy level, and diversification rate, with character selection partly based on findings in mosses and liverworts. Results Hornworts underwent numerous transitions between monoicy and dioicy. The transition rate from dioicy to monoicy was 2× higher than in the opposite direction, but monoicous groups have higher extinction rates; diversification rates do not correlate with sexual system. A correlation important in mosses, that between monoicy and polyploidy, apparently plays a small role: of 20 species with chromosome counts, only one is polyploid, the monoicous Anthoceros punctatus . A contingency test revealed that transitions to dioicy were more likely in species with small spores, supporting the hypothesis that small but numerous spores may be advantageous for dioicous species that depend on dense carpets of gametophytes for reproductive assurance. However, we found no evidence for increased antheridium-per-chamber numbers in dioicous species. Conclusions Sexual systems in hornworts are labile, and the higher number of extant monoicous species (60%) may be largely due to frequent transitions to monoicy.
-
A three-genome phylogeny of Momordica (Cucurbitaceae) suggests seven returns from dioecy to Monoecy and recent long-distance dispersal to Asia.
Molecular phylogenetics and evolution, 2009Co-Authors: Hanno Schaefer, Susanne S RennerAbstract:The bitter gourd genus Momordica comprises 47 species in Africa and 12 in Asia and Australia. All have unisexual flowers, and of the African species, 24 are dioecious, 23 monoecious, while all Asian species are dioecious. Maximum likelihood analyses of 6257 aligned nucleotides of plastid, mitochondrial and nuclear DNA obtained for 122 accessions of Momordica and seven outgroups show that Momordica is monophyletic and consists of 11 well-supported clades. Monoecy evolved from dioecy seven times independently, always in Africa and mostly in savanna species with low population densities. Leaky dioecy, with occasional fruit-producing males, occurs in two African species and might be the first step in an evolutionary transition towards Monoecy. Dated biogeographic analyses suggest that Momordica originated in tropical Africa and that the Asian species are the result of one long-distance dispersal event about 19 million years ago. The pantropical vegetable Momordica charantia is of African, not Asian origin as had previously been suggested.
-
hybridization polyploidy and evolutionary transitions between Monoecy and dioecy in bryonia cucurbitaceae
American Journal of Botany, 2008Co-Authors: Stefanie M Volz, Susanne S RennerAbstract:Correns’s 1903 (Berichte der Deutschen Botanischen Gesellschaft 21: 133 – 147) crosses between a monoecious and a dioecious species of Bryonia revealed the simple Mendelian inheritance of dioecy and provided the first instance of an XY sex determination system in any organism. Bryonia ranges from the Canary Islands to Central Asia and comprises seven dioecious and three monoecious species; its closest relative, Ecballium elaterium, has dioecious and monoecious populations. We used chloroplast (cp) and nuclear (nr) gene phylogenies to infer sexual system evolution in Bryonia. We also tested for associations between sexual system and ploidy level, based on published and original chromosome counts. Conflicts between cp and nr topologies imply that the dioecious hexaploid B. cretica arose from hybridization(s), probably involving the dioecious diploids B. dioica, B. syriaca, and/or B. multiflora. A tetraploid dioecious endemic on Corsica and Sardinia probably originated from B. dioica via autopolyploidy. While the cp phylogeny resolves few species relationships, the nr tree implies at least two evolutionary changes in sexual system. There is no correlation between sexual system and ploidy level. Molecular clocks suggest that the deepest divergence, between a species on the Canary Islands and the ancestor of all remaining species, occurred ca. 10 million years ago.
Jannice Friedman - One of the best experts on this subject based on the ideXlab platform.
-
the consequences of Monoecy and protogyny for mating in wind pollinated carex
New Phytologist, 2009Co-Authors: Jannice Friedman, Spencer C H BarrettAbstract:Summary • Monoecy and protogyny are widespread in wind-pollinated plants and have been interpreted as outcrossing mechanisms, though few studies have investigated their function. Carex, a large genus of anemophilous herbs, is predominantly monoecious and many species are protogynous. We investigated whether Monoecy and protogyny limit self-pollination in seven Carex species. • We conducted field experiments comparing stigmatic pollen loads and seed set between intact and emasculated stems. We tested for self-compatibility and evaluated pollen limitation of seed set by supplemental pollination. Finally, we measured outcrossing rates in open-pollinated and emasculated stems using allozyme markers. • Emasculated stems captured significantly less pollen than open-pollinated stems and set less seed. Pollen deposition during the female-only phase for intact stems was only 12% of the total captured. Outcrossing rates for three species indicated high selfing (range t = 0.03–0.39). Allozyme loci in the remaining species were monomorphic also suggesting high selfing. These results demonstrate that neither Monoecy nor protogyny is particularly effective at limiting self-fertilization. • Selection for the avoidance of selfing is unlikely to maintain Monoecy in many Carex species although protogyny may provide limited opportunities for outcrossing. We propose that geitonogamy in self-compatible wind-pollinated species with unisexual flowers may be widespread and provides reproductive assurance.
-
The consequences of Monoecy and protogyny for mating in wind‐pollinated Carex
The New phytologist, 2008Co-Authors: Jannice Friedman, Spencer C H BarrettAbstract:Summary • Monoecy and protogyny are widespread in wind-pollinated plants and have been interpreted as outcrossing mechanisms, though few studies have investigated their function. Carex, a large genus of anemophilous herbs, is predominantly monoecious and many species are protogynous. We investigated whether Monoecy and protogyny limit self-pollination in seven Carex species. • We conducted field experiments comparing stigmatic pollen loads and seed set between intact and emasculated stems. We tested for self-compatibility and evaluated pollen limitation of seed set by supplemental pollination. Finally, we measured outcrossing rates in open-pollinated and emasculated stems using allozyme markers. • Emasculated stems captured significantly less pollen than open-pollinated stems and set less seed. Pollen deposition during the female-only phase for intact stems was only 12% of the total captured. Outcrossing rates for three species indicated high selfing (range t = 0.03–0.39). Allozyme loci in the remaining species were monomorphic also suggesting high selfing. These results demonstrate that neither Monoecy nor protogyny is particularly effective at limiting self-fertilization. • Selection for the avoidance of selfing is unlikely to maintain Monoecy in many Carex species although protogyny may provide limited opportunities for outcrossing. We propose that geitonogamy in self-compatible wind-pollinated species with unisexual flowers may be widespread and provides reproductive assurance.
-
the evolution and maintenance of Monoecy and dioecy in sagittaria latifolia alismataceae
Evolution, 2002Co-Authors: Marcel E Dorken, Jannice Friedman, Spencer C H BarrettAbstract:Abstract Plant species rarely exhibit both monoecious and dioecious sexual systems. This limits opportunities to investigate the consequences of combined versus separate sex function on mating patterns and genetic variation and the analysis of factors responsible for the evolution and maintenance of the two sexual systems. Populations of the North American clonal aquatic Sagittaria latifolia are usually either monoecious or dioecious and often grow in close geographic proximity. We investigated mating patterns, genetic structure, and relationships between the two sexual systems using allozyme variation in populations from southern Ontario, Canada. As predicted, selfing rates in monoecious populations (n = 6, mean = 0.41) were significantly higher than in dioecious populations (n = 6, mean = 0.11). Moreover, marker-based estimates of inbreeding depression (δ) indicated strong selection against inbred offspring in both monoecious (mean δ = 0.83) and dioecious (mean δ = 0.84) populations. However, the differ...
-
the evolution and maintenance of Monoecy and dioecy in sagittaria latifolia alismataceae
Evolution, 2002Co-Authors: Marcel E Dorken, Jannice Friedman, Spencer C H BarrettAbstract:Plant species rarely exhibit both monoecious and dioecious sexual systems. This limits opportunities to investigate the consequences of combined versus separate sex function on mating patterns and genetic variation and the analysis of factors responsible for the evolution and maintenance of the two sexual systems. Populations of the North American clonal aquatic Sagittaria latifolia are usually either monoecious or dioecious and often grow in close geographic proximity. We investigated mating patterns, genetic structure, and relationships between the two sexual systems using allozyme variation in populations from southern Ontario, Canada. As predicted, selfing rates in monoecious populations (n = 6, mean = 0.41) were significantly higher than in dioecious populations (n = 6, mean = 0.11). Moreover, marker-based estimates of inbreeding depression (delta) indicated strong selection against inbred offspring in both monoecious (mean delta = 0.83) and dioecious (mean delta = 0.84) populations. However, the difference in selfing rate between the sexual systems was not reflected in contrasting levels of genetic variation. Our surveys of 12 loci in 15 monoecious and 11 dioecious populations revealed no significant differences in the proportion of polymorphic loci (P), number of alleles per locus (A), or observed and expected heterozygosity (H(o) and H(e), respectively). Strong inbreeding depression favoring survival of outcrossed offspring may act to maintain similar levels of diversity between monoecious and dioecious populations. Despite geographical overlap between the two sexual systems in southern Ontario, a dendrogram of genetic relationships indicated two distinct clusters of populations largely corresponding to monoecious and dioecious populations. Reproductive isolation between monoecious and dioecious populations appears to be governed, in part, by observed differences in habitat and life history. We suggest that selfing and inbreeding depression in monoecious populations are important in the transition from Monoecy to dioecy and that the maintenance of distinct sexual systems in S. latifolia is governed by interactions between ecology, life history, and mating.
-
The evolution and maintenance of Monoecy and dioecy in Sagittaria latifolia (Alismataceae).
Evolution; international journal of organic evolution, 2002Co-Authors: Marcel E Dorken, Jannice Friedman, Spencer C H BarrettAbstract:Plant species rarely exhibit both monoecious and dioecious sexual systems. This limits opportunities to investigate the consequences of combined versus separate sex function on mating patterns and genetic variation and the analysis of factors responsible for the evolution and maintenance of the two sexual systems. Populations of the North American clonal aquatic Sagittaria latifolia are usually either monoecious or dioecious and often grow in close geographic proximity. We investigated mating patterns, genetic structure, and relationships between the two sexual systems using allozyme variation in populations from southern Ontario, Canada. As predicted, selfing rates in mon- oecious populations (n 5 6, mean 5 0.41) were significantly higher than in dioecious populations (n 5 6, mean 5 0.11). Moreover, marker-based estimates of inbreeding depression (d) indicated strong selection against inbred offspring in both monoecious (mean d5 0.83) and dioecious (mean d5 0.84) populations. However, the difference in selfing rate between the sexual systems was not reflected in contrasting levels of genetic variation. Our surveys of 12 loci in 15 monoecious and 11 dioecious populations revealed no significant differences in the proportion of polymorphic loci (P), number of alleles per locus (A), or observed and expected heterozygosity (Ho and He, respectively). Strong inbreeding depression favoring survival of outcrossed offspring may act to maintain similar levels of diversity between monoecious and dioecious populations. Despite geographical overlap between the two sexual systems in southern Ontario, a dendrogram of genetic relationships indicated two distinct clusters of populations largely corresponding to monoecious and dioecious populations. Reproductive isolation between monoecious and dioecious populations appears to be governed, in part, by observed differences in habitat and life history. We suggest that selfing and inbreeding depression in monoecious populations are important in the transition from Monoecy to dioecy and that the maintenance of distinct sexual systems in S. latifolia is governed by interactions between ecology, life history, and mating.
Abdelhafid Bendahmane - One of the best experts on this subject based on the ideXlab platform.
-
The andromonoecious sex determination gene predates the separation of cucumis and citrullus genera
PLoS ONE, 2016Co-Authors: Adnane Boualem, Marieagnes Sari, Christelle Troadec, Catherine Dogimont, Afef Lemhamdi, Sarah Pignoly, Fadi Abou Choucha, Ilkour Solmaz, Nebahat Sari, Abdelhafid BendahmaneAbstract:Understanding the evolution of sex determination in plants requires the cloning and the characterization of sex determination genes. Monoecy is characterized by the presence of both male and female flowers on the same plant. AndroMonoecy is characterized by plants carrying both male and bisexual flowers. In watermelon, the transition between these two sexual forms is controlled by the identity of the alleles at the A locus. We previously showed, in two Cucumis species, melon and cucumber, that the transition from Monoecy to androMonoecy results from mutations in 1-aminocyclopropane-1-carboxylic acid synthase (ACS) gene, ACS-7/ACS2. To test whether the ACS-7/ACS2 function is conserved in cucurbits, we cloned and characterized ClACS7 in watermelon. We demonstrated co-segregation of ClACS7, the homolog of CmACS-7/CsACS2, with the A locus. Sequence analysis of ClACS7 in watermelon accessions identified three ClACS7 isoforms, two in andromonoecious and one in monoecious lines. To determine whether the andromonoecious phenotype is due to a loss of ACS enzymatic activity, we expressed and assayed the activity of the three protein isoforms. Like in melon and cucumber, the isoforms from the andromonoecious lines showed reduced to no enzymatic activity and the isoform from the monoecious line was active. Consistent with this, the mutations leading androMonoecy were clustered in the active site of the enzyme. Based on this, we concluded that active ClACS7 enzyme leads to the development of female flowers in monoecious lines, whereas a reduction of enzymatic activity yields hermaphrodite flowers. ClACS7, like CmACS-7/CsACS2 in melon and cucumber, is highly expressed in carpel primordia of buds determined to develop carpels and not in male flowers. Based on this finding and previous investigations, we concluded that the Monoecy gene, ACS7, likely predated the separation of the cucumis and citrullus genera.
-
A Conserved Ethylene Biosynthesis Enzyme Leads to AndroMonoecy in Two Cucumis Species
2013Co-Authors: Adnane Boualem, Irina Kovalski, Marieagnes Sari, Christelle Troadec, Rafael Perl-treves, Abdelhafid BendahmaneAbstract:AndroMonoecy is a widespread sexual system in angiosperms, characterized by plants carrying both male and bisexual flowers. Monoecy is characterized by the presence of both male and female flowers on the same plant. In cucumber, these sexual forms are controlled by the identity of the alleles at the M locus. In melon, we recently showed that the transition from Monoecy to androMonoecy result from a mutation in 1-aminocyclopropane-1-carboxylic acid synthase (ACS) gene, CmACS-7. To isolate the androMonoecy gene in cucumber we used a candidate gene approach in combination with genetical and biochemical analysis. We demonstrated co-segregation of CsACS2, a close homolog of CmACS-7, with the M locus. Sequence analysis of CsACS2 in cucumber accessions identified four CsACS2 isoforms, three in andromonoecious and one in monoecious lines. To determine whether the andromonoecious phenotype is due to a loss of ACS enzymatic activity, we expressed the four isoforms in Escherichia coli and assayed their activity in vitro. Like in melon, the isoforms from the andromonoecious lines showed reduced to no enzymatic activity and the isoform from the monoecious line was active. Consistent with this, the mutations leading androMonoecy were clustered in the active site of the enzyme. Based on this, we concluded that active CsACS2 enzyme leads to the development of female flowers in monoecious lines, whereas a reduction of enzymatic activity yields hermaphrodite flowers. Consistent with this, CsACS2, like CmACS-7 in melon, is expressed specifically in carpel primordia of buds determined to develop carpels. Following ACS expression, inter-orga
-
a conserved ethylene biosynthesis enzyme leads to androMonoecy in two cucumis species
PLOS ONE, 2009Co-Authors: Adnane Boualem, Irina Kovalski, Marieagnes Sari, Christelle Troadec, Rafael Perltreves, Abdelhafid BendahmaneAbstract:AndroMonoecy is a widespread sexual system in angiosperms, characterized by plants carrying both male and bisexual flowers. Monoecy is characterized by the presence of both male and female flowers on the same plant. In cucumber, these sexual forms are controlled by the identity of the alleles at the M locus. In melon, we recently showed that the transition from Monoecy to androMonoecy result from a mutation in 1-aminocyclopropane-1-carboxylic acid synthase (ACS) gene, CmACS-7. To isolate the androMonoecy gene in cucumber we used a candidate gene approach in combination with genetical and biochemical analysis. We demonstrated co-segregation of CsACS2, a close homolog of CmACS-7, with the M locus. Sequence analysis of CsACS2 in cucumber accessions identified four CsACS2 isoforms, three in andromonoecious and one in monoecious lines. To determine whether the andromonoecious phenotype is due to a loss of ACS enzymatic activity, we expressed the four isoforms in Escherichia coli and assayed their activity in vitro. Like in melon, the isoforms from the andromonoecious lines showed reduced to no enzymatic activity and the isoform from the monoecious line was active. Consistent with this, the mutations leading androMonoecy were clustered in the active site of the enzyme. Based on this, we concluded that active CsACS2 enzyme leads to the development of female flowers in monoecious lines, whereas a reduction of enzymatic activity yields hermaphrodite flowers. Consistent with this, CsACS2, like CmACS-7 in melon, is expressed specifically in carpel primordia of buds determined to develop carpels. Following ACS expression, inter-organ communication is likely responsible for the inhibition of stamina development. In both melon and cucumber, flower unisexuality seems to be the ancestral situation, as the majority of Cucumis species are monoecious. Thus, the ancestor gene of CmACS-7/CsACS2 likely have controlled the stamen development before speciation of Cucumis sativus (cucumber) and Cucumis melo (melon) that have diverged over 40 My ago. The isolation of the genes for androMonoecy in Cucumis species provides a molecular basis for understanding how sexual systems arise and are maintained within and between species.