is more common among the dicots than the monocots (Renner and Ricklefs, 1995). Dioecy is a breeding system that promotes cross-pollination in Poa is a large, diverse genus that belongs to the subplants. The transfer of this trait into economically important selfpollinated cereal crops would revolutionize the production of hybrids family Pooideae of the Poaceae. Several species are in these spec...

Comparing species richness in sister clades that differ in a character state is one of the ways to study factors influencing diversification. While most of its applications have focussed on traits that increase diversification, some have been used to study the association of a trait with lower species richness, e.g., the occurrence of dioecy in flowering plants. We show here, using simulations ...

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 deter...

It is generally accepted that dioecious plants occur more frequently in dry and nutrient-poor habitats, suggesting that abiotic stress factors could contribute to evolution of dioecy from hermaphrodite. Therefore, experimental investigations on the responses of subdioecious species, a special sexual system comprising male, female, and hermaphrodite plants, to abiotic stress factors could quanti...

The evolution of plants exhibiting different sexes, or dioecy, is correlated with a number of ecological and life-history traits such as woody growth form and animal-dispersed seeds, but the underlying causes of these associations are unclear. Previous work in seed plants has suggested that the evolution of fleshy cones or seeds may favour dioecy. In this study, we use a well-sampled molecular ...

Rainforests in tropical Australia occupy a very small, discontinuous area (<1% of the continent), yet they are floristically diverse (c. 2800 vascular species) with high endemicity. There is a distinctive Gondwanan and autochthonous element, and some of the world's ancestral links to the basal angiosperms are uniquely found here. The rainforests can be evergreen or deciduous, but there is a dis...

Understanding the evolution of sex determination in plants requires identifying the mechanisms underlying the transition from monoecious plants, where male and female flowers coexist, to unisexual individuals found in dioecious species. We show that in melon and cucumber, the androecy gene controls female flower development and encodes a limiting enzyme of ethylene biosynthesis, ACS11. ACS11 is...

Sex allocation (SA) models are traditionally based on the implicit assumption that hermaphroditism must meet criteria that make it stable against transition to dioecy. This, however, puts serious constraints on the adaptive values that SA can attain. A transition to gonochorism may, however, be impossible in many systems and therefore realized SA in hermaphrodites may not be limited by conditio...

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 Momord...