Ecological interactions affecting the evolutionof plant mating systems: Current research and future directions
Freeman, Carl , Sinclair, Jordan .
The Evolution of Dioecy: The Interactions of Inbreeding, Compensation and Specialization.
We developed two models to explore the evolution of dioecious plants. In the first, a genetic model, we used a two locus two allele model with independent segregation of loci and dominant mutations; In the second model, a phenotypic model, mating between males and females produced a1:1 offspring sex ratio, mating between hermaphrodites and unisexuals results in half hermaphrodites and half of the unisexual gender that the hermaphrodite mated with. Matings between hermaphrodites produces only hermaphrodites. The genetic model allows for the formation of neuters (double mutants) - in fact neuters often represent 20% or more of resulting dioecious populations. We developed the phenotype model as an extreme at the opposite end. In this case no neuters are produced. Obviously this assumes that assortment is not independent. We examined the effect of inbreeding including incest (consanguineous mating and selfing as opposed to just selfing), compensation (the production of additional reproductive structures of one sex because the structures of the opposite sex were not produced) and specialization (the ability to better disperse pollen or fruits). Our results show that when we ignored consanguineous mating it was possible, though not likely for unisexuals to invade a hermaphroditic population. The addition of incest alone allowed the unisexual males to invade more frequently and under less stringent conditions,but not females. With either model, compensation did not facilitate the invasion of unisexuals, if it was the only factor affecting evolution. However,if inbreeding depression and/or specialization was acting in addition to compensation then compensation enhanced the invasibility. When all three factors were involved then males and females invaded, and under the phenotypic model, purely dioecious populations were formed. Ignoring the formation of neuters, there are few qualitative differences between the outcomes of the genotypic and phenotypic models. Our results indicate that specialization is important in facilitating the evolution of dioecy. Put into ecological terms,this suggests that the ability to disperse pollen and seed is extremely important in the evolution of dioecious species. Recent research suggests that most dioecious species are found early in succession, when colonization and the ability to disperse pollen over long distances would be at a premium.
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1 - Wayne State Univ, Dept. Biological Science, 1360 Biological Sciences, Detroit, MI, 48202, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Delaware D/Hyatt
Date: Tuesday, July 10th, 2012
Time: 2:10 PM