Hybridization, polyploidy, and evolutionary transitions between monoecy and dioecy in Bryonia (Cucurbitaceae)

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

Testing mechanisms of compensatory fitness of dioecy in a cosexual world

Questions: All else being equal, populations of dioecious species with a 50:50 sex ratio have only half the effective reproductive population size of bisexual species of equal abundance. Consequently, there is a need to explain how dioecious and bisexual species coexist. Increased mean individual seed mass, fecundity, and population density have all been proposed as attributes of unisexual individuals or populations that may contribute to the persistence or resilience of dioecious species. To date, no studies have compared sympatric dioecious and cosexual species with respect to all three components of fitness. In this study, we sought evidence for these compensatory advantages (higher seed mass, greater seed production per unit basal area, and higher population density) in dioecious species. Location: Five 20–25 ha forest dynamic plots spanning a latitudinal gradient in China, including two temperate, two subtropical, and one tropical forest. Methods: We used a phylogenetically corrected generalized linear modelling approach to assess the phylogenetic dependence and joint evolution of sexual system, seed mass and production, and ecological abundances among 48–333 species and 32,568–136,237 individuals per forest. Results: Across all five forests, we detected no consistent advantage for dioecious relative to sympatric cosexual species with respect to mean individual seed mass, seed production or the density of stems in any size class. Conclusions: Our study suggests that seed traits may provide compensatory mechanisms in some forests, but most often the coexistence of sexual systems cannot be explained by advantages of dioecy related to seed quality and demographic parameters. Future investigations of the factors that promote coexistence may increase our understanding by expanding the search to include attributes such as lifespan and tolerance or resistance to herbivores

Characterization of a large sex determination region in Salix purpurea L. (Salicaceae).

Dioecy has evolved numerous times in plants, but heteromorphic sex chromosomes are apparently rare. Sex determination has been studied in multiple Salix and Populus (Salicaceae) species, and P. trichocarpa has an XY sex determination system on chromosome 19, while S. suchowensis and S. viminalis have a ZW system on chromosome 15. Here we use whole genome sequencing coupled with quantitative trait locus mapping and a genome-wide association study to characterize the genomic composition of the non-recombining portion of the sex determination region. We demonstrate that Salix purpurea also has a ZW system on chromosome 15. The sex determination region has reduced recombination, high structural polymorphism, an abundance of transposable elements, and contains genes that are involved in sex expression in other plants. We also show that chromosome 19 contains sex-associated markers in this S. purpurea assembly, along with other autosomes. This raises the intriguing possibility of a translocation of the sex determination region within the Salicaceae lineage, suggesting a common evolutionary origin of the Populus and Salix sex determination loci

Incidence, correlates, and origins of dioecy in the Island Flora of New Caledonia

Premise of research. Because it is an inherently risky sexual system, dioecy is globally rare. Attempts to explain unusually high incidences of dioecy on certain islands have generated a considerable literature on the relationships among dioecy, its ecological correlates, establishment after transoceanic dispersal, and postdispersal speciation. Nevertheless, few studies of dioecy on islands have included considerations of the origins and maintenance of dioecy on islands along with determinations of its incidence. Methodology. We used the literature, herbarium specimens, and fieldwork to determine the incidence of dioecy in the native angiosperm flora of New Caledonia. We inferred the number and characteristics of colonists needed to account for the extant dioecious flora. We made traditional species-based numerical assessments of associations between dioecy on New Caledonia and woodiness, plain flowers, fleshy fruit, habitat, and endemism, and we constructed a phylogenetic tree for New Caledonia's native angiosperms to investigate correlated evolution of dioecy and those associated traits. Pivotal results. This study is the first comprehensive survey of sexual systems for the flora of New Caledonia. One-fifth of New Caledonia's native angiosperms are dioecious. Dioecy is numerically overrepresented among species that are woody, have plain flowers, have fleshy fruit, occur in rainforest, or are endemic. However, we found strong evidence for correlated evolution only for dioecy and woodiness, plain flowers, and fleshy fruit. Dioecious groups with more of the widely accepted morphological correlates of dioecy tend to be more speciose. Approximately 90% of the colonists that gave rise to the extant dioecious flora were themselves dioecious. Approximately 60% of the colonists have two or more dioecious descendants, and those descendants comprise more than 90% of the extant dioecious species. Conclusions. Successful dispersal and establishment of already dioecious colonists and autochthonous speciation of dioecious lineages are primarily responsible for the high incidence of dioecy on New Caledonia. There were relatively few postdispersal transitions to dioecy. The associations of dioecy with woodiness, plain flowers, and fleshy fruit result from correlated evolution that occurred prior to dispersal to New Caledonia, while the associations of dioecy with rainforest habitat and endemism appear to result from autochthonous speciation of dioecious lineages. With similar to similar to 4% of the world's dioecious species occurring only there, New Caledonia should be a rich source of new information on the evolutionary ecology of dioecy. Realization of this potential will require both further study and concerted efforts to preserve the native flora

Coccinia intermedia

Nuclear and plastid sequences from two individuals of a suspected new species of Coccinia from West Africa were added to an available molecular phylogeny for the remaining 27 species of the genus. Phylogenetic analyses of these data indicate the new species' monophyletic status and closest relatives. Based on four fertile collections, we here describe and illustrate Coccinia intermedia Holstein. We also provide a key to the Coccinia species of West Africa and map their distributions

Flower Biology of Two Diospyros Species Neighborly Live at Csc Area: Do Pollen Viability and Tube Growth Rate Shire Endemic Distribution

Aims of study were to compare flower structure, pollen viability and pollen tube growth rate of two Diospyros species neighborly live in Cibinong Science Centre (CSC) park, Diospyros blancoi and D. celebica, and pursue if pollen-tube growth rate shire reasons endemic distribution of D.celebica in native habitat. Floral structurewas in situ or ex situ morphologically observed. Germination test and pollen tube growth incubation were done in Sarfatti medium and digitally captured and computerize analysis. The result showed that, both species have flower part resemblance each other. D. blancoi has bigger size in almost all flower parts. D. blancoi showed much more pollen viability (41% vs 7%) and tube growth rate than D. celebica1 (66 vs 0.57 μm per minute). Average pollen-tube length of both species at about 31/2 hours incubation was significantly different each other (342.679 ± 37.067 vs 128,673 ± 49,215μm). Most observed D. blancoi female trees set high number of fruit year to year and almost observed D. celebica female trees set very low number of fruit and some time without fruit in the year. It is associated with geographical distribution difference between the two species. Very significantlydifferent in pollen-germination percentage and pollen-tube growth rate provide a tool of further study to know microenvironment for reproduction and propagation of the endemic species, D. celebica

Global distribution and evolutionary transitions of angiosperm sexual systems

Angiosperm sexual systems are fundamental to the evolution and distribution of plant diversity, yet spatiotemporal patterns in angiosperm sexual systems and their drivers remain poorly known. Using data on sexual systems and distributions of 68453 angiosperm species, we present the first global maps of sexual system frequencies and evaluate sexual system evolution during the Cenozoic. Frequencies of dioecy and monoecy increase with latitude, while hermaphrodites are more frequent in warm and arid regions. Transitions to dioecy from other states were higher than to hermaphroditism, but transitions away from dioecy increased since the Cenozoic, suggesting that dioecy is not an evolutionary end point. Transitions between hermaphroditism and dioecy increased, while transitions to monoecy decreased with paleo-temperature when paleo-temperature >0℃. Our study demonstrates the biogeography of angiosperm sexual systems from a macroecological perspective, and enhances our understanding of plant diversity patterns and their response to climate change.acceptedVersio

Dicliny in Bouteloua (Poaceae: Chloridoideae): Implications for the Evolution of Dioecy

The New World grass genus Bouteloua (Chloridoideae: Cynodonteae) comprises 57 species, 13 of which produce unisexual spikelets and hence are diclinous. Andromonoecy, gynodioecy, monoecy, trimonoecy, and dioecy all occur in the genus, and ten species are known to express more than one of these breeding systems. Employing a phylogenetic estimate based on parsimony analysis of DNA sequences from the ITS (nrDNA) and trnL–F (cpDNA) regions representing 35 species of Bouteloua, including ten of 13 diclinous species, we used parsimony character state reconstructions to investigate the evolution of unisexual spikelets and breeding systems. Our specific goals were to estimate (1) the ancestral condition in the genus, (2) the number of times spikelet unisexuality has arisen and/or been lost, and (3) the evolutionary pathways leading to dioecy and the other breeding systems. Although a number of related genera are diclinous, the reconstructions suggest that the common ancestor of Bouteloua probably was not diclinous. Spikelet unisexuality appears to have evolved two to seven times in the genus, but precisely how many times is uncertain; zero to four reversals to hermaphroditism are inferred. The reconstructions show andromonoecy arising from monoecy, and gynodioecy arising from monocliny. Neither andromonoecy nor gynodioecy are implicated in the origin of monoecy or dioecy. Monoecy is shown to evolve from monocliny and dioecy, and dioecy from monocliny and monoecy. Polyploidy and arid environments are possible factors in the evolution and variability of breeding systems in Bouteloua