Patterns and Mechanisms of Evolution of Island Plants
Weller, Stephen G. , Sakai, Ann K. , Campbell, Diane R. , Culley, Theresa M. .
The quantitative genetic basis of breeding system evolution in Schiedea (Caryophyllaceae) in the Hawaiian Islands.
The remarkable diversity of breeding systems in Schiedea, a radiation of 34 species endemic to the Hawaiian Islands, provides an opportunity to investigate patterns of resource allocation associated with the evolution of dioecy. At least two transitions from hermaphroditism to sexual dimorphism are likely, and all sexually dimorphic species of Schiedea occur in dry, usually windy habitats. Wind pollination appears critical for the success of females in these environments. Sexually dimorphic species range from those where females are rare in populations and co-occur with hermaphrodites, to dioecious species where females and males are equally frequent. Significant heritable genetic variation occurs for allocation to male and female biomass in S. salicaria, a gynodioecious species with 12% females, and for S. adamantis, a gynodioecious species with 39% females. There are no negative genetic correlations between allocation to female and male biomass that would be expected with tradeoffs in male and female function. Positive genetic correlations for allocation to female function occur across the sexes. Despite these intersex genetic correlations, there was a positive response to artificial selection for high allocation to female biomass in females of S. salicaria. There was also a positive response to artificial selection for high allocation to male biomass in hermaphrodites. No differences in seed production could be detected for females and hermaphrodites of S. salicaria in the field. In contrast, striking differences in female function were detected between the sexes of S. adamantis, a species that appears to have evolved resource allocation patterns more closely resembling fully dioecious species. In gynodioecious populations, wind pollination and the presence of females are likely to favor hermaphrodites with increasing allocation to male function. The underlying genetic structure of these gynodioecious species suggests that differences in allocation patterns could increase in subsequent generations, and favor the evolution of full dioecy.
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1 - University of California, Irvine, Department of Ecology and Evolution, 321 Steinhaus Hall, UCI, Irvine, California, 92697, USA
2 - University of Cincinnati, Department of Biological Sciences, 614 Rieveschl Hall, Cincinnati, Ohio, 45221, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Salon J - Austin Grand Ballroom/Hilton
Date: Wednesday, August 17th, 2005
Time: 4:30 PM