Heterostyly: speciation within a species

Almost all organisms in nature show nonrandom mating to different degrees. Two extreme results of nonrandom mating are speciation and sexual differentiation. Heterostyly is a form of sexual differentiation considered to have evolved to resolve conflicts between male and female functions of hermaphrodite flowers. Our study examines necessary and sufficient conditions for establishment of heterostyly using a configuration individual-based model. Previous models assume invasion of a mutant phenotype into a population with monomorphic wild phenotype. In contrast, our model demonstrates that heterostyly can be established from a population with continuous phenotypic variation, a proposition that requires simpler assumptions than the previous hypotheses. Results of our simulation show that genetic linkage between stigma and anther heights is essential for establishment of heterostyly. Dominance effects on the genes for stamen or stigma heights are not necessary, but they promote evolution of heterostyly. Probability of evolution of heterostyly also depends on the functional relationship between stigma–anther distance and strength of sexual interference, and the distance and probability of pollen deposition success. Parallelity and difference between speciation and sexual differentiation are also discussed

Relationships and floral biology of Bidens cosmoides (Asteraceae)

p. [23]-32: ill.; 23 cm.Bidens cosmoides, in the monotypic section Degeneria, is a morphologically unique species endemic to Kaua'i. Contrary to previous reports it will hybridize successfully with other Hawaiian species of Bidens, all in section Campylotheca. All Hawaiian species of Bidens are interfertile, suggesting that they are the products of adaptive radiation from a single ancestral introduction rather than two separate introductions and lineages as previously postulated. The elongated styles of B. cosmoides, exserted 20-30 mm beyond the corollas, that present pollen on the style tips, are unique in the genus. Flowers produce more than 30 times as much nectar by volume than do other Hawaiian species of Bidens, but the sugar concentration of the nectar is only half that of other species (30% vs. 60%). These unique floral features appear to represent adaptations to pollination by birds, although pollination of B. cosmoides has not yet been observed in nature

New taxa and new combinations in Hawaiian Bidens (Asteraceae)

p. [1]-16: ill.; 23 cm.In the course of our investigation of the genetics of adaptive radiation and evolution of Bidens in the Hawaiian Islands, it has been necessary to revise the group taxonomically. Here we describe four new subspecies and make three new combinations at the rank of subspecies. Bidens sandvicensis ssp. confusa Nagata & Ganders, B. hillebrandiana ssp. polycephala Nagata & Ganders, B. micrantha ssp. kalealaha Nagata & Ganders, and B. forbesii ssp. kahiliensis Ganders & Nagata are described as new. Bidens campylotheca ssp. pentamera (Sherff) Ganders & Nagata, B. menziesii ssp. filijormis (Sherff) Ganders & Nagata, and B. micrantha ssp. ctenophylla (Sherff) Nagata & Ganders are published as new combinations at subspecific rank. A key to all taxa of Bidens in the Hawaiian Islands is provided. It includes introduced taxa that have been collected in the islands in the last 80 years