RESUMEN
Breeding system, sexual system, temporal variation in sex expression and herkogamy were evaluated in seven herbaceous-shrubby communities from the Gran Sabana Plateau, Venezuela. This analysis was conducted considering the life form, substrate type, succulence, carbon metabolism, nutritional relation, successional stage, pollination system specificity and endemism of plant species. Of the 348 plant species studied, 73.8 % were hermaphrodite, 16.9 % were monoecious and 9.2 % were dioecious. Plant sexual systems such as dichogamy and herkogamy were associated with life form, nutritional relations, carbon metabolism and pollination systems. Most species were adichogamous, followed by protandrous and protogynous. Protandry was high for perennial herbs, annual herbs and trees, and protogyny was most frequent in perennial herbs. Protandrous and protogynous species were frequently anemophilous. Herkogamy was higher than non-herkogamy. Herkogamy was higher for trees, shrubs and liana; higher in monophilous and lower in anemophilous species. Most of the hermaphrodites were herkogamous and adichogamous species. In contrast, monoecy were commonly perennial herb and dichogamous species and frequently associated with anemophily. Dioecious species were trees and shrubs and with polyphilous pollination. Dioecy was the most frequent sexual system for endemic species. Hermaphrodite species were similarly distributed across plant communities. Monoecy was slightly higher for savanna and fallow than the other communities, and dioecy was higher for shrublands and secondary bushland. Most plant species were non-agamospermous, non-spontaneous self-pollinated and xenogamous. Partially self-incompatible dominated, followed by self-incompatible, partially cross-incompatible and the lowest frequency corresponded to cross-incompatible species. All these results are discussed in the context of evolutionary and ecological trends.
RESUMEN
The cataloging of the vascular plants of the Americas has a centuries-long history, but it is only in recent decades that an overview of the entire flora has become possible. We present an integrated assessment of all known native species of vascular plants in the Americas. Twelve regional and national checklists, prepared over the past 25 years and including two large ongoing flora projects, were merged into a single list. Our publicly searchable checklist includes 124,993 species, 6227 genera, and 355 families, which correspond to 33% of the 383,671 vascular plant species known worldwide. In the past 25 years, the rate at which new species descriptions are added has averaged 744 annually for the Americas, and we can expect the total to reach about 150,000.
