PARENT SESSION
Oral Session # 46: Evolutionary Ecology I: Plants.
Presiding: P Minchin
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 201.
The influences of ecological processes on stigma-height dimorphic species.
Zhang, Yu*,1, Baker, Angela2, Wilson, William1, 1 Duke University, Durham, NC2 University of Oulu, Oulu, FI
ABSTRACT- Species exhibiting stigma-height dimorphism are composed of two floral morphs differing in stigma-height. In long-styled plants (L-morph), the stigma is exserted beyond the stamen, whereas in short-styled plants (S-morph), the stigma is lower. It is commonly believed that a stigma-height dimorphism is established when each morph is more proficient at pollinating the other morph than plants of its own type and the two morphs do not differ in the proficiency of autogamous or geitonogamous pollination. These mating patterns will result in an isoplethic (1L:1S) equilibrium morph ratio; however observed morph ratios in many stigma-height dimorphic species range widely from isoplethy to populations fixed for the L-morph. We explored how the morph ratio of stigma-height dimorphic species is affected by factors such as selfing rate, intra- and intermorph pollination, pollen limitation, ovule fertilization probability, and population size by using both analytical and simulation models of plant population dynamics in an ecological context. Comparisons between our simulation results and empirical data of self-sterile Narcissus assoanus and self-compatible N. dubius supported several predictions. For the self-sterile N. assoanus, population size-dependent L-biased morph ratios are due either to a greater degree of disassortative mating in the L-morph and pollen limitation in large populations, or greater ovule fertilization probability in L-morph and pollen limitation in small populations. For the self-compatible species N. dubius, strongly L-biased morph ratios independent of population size may be due to lethality of homozygous S-morph.
Key words: morph-ratios, mathematical model, stigma-height dimorphism, pollen limitation