CULLEY, THERESA M.1,2*, ANN K. SAKAI1, STEPHEN G. WELLER1, and DIANE R. CAMPBELL1. 1Department of Ecology and Evolutionary Biology, University of California-Irvine, Irvine, CA 92697-2525; 2Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221-0006. - The quantitative genetics of sex allocation in gynodioecious Schiedea salicaria (Caryophyllaceae).
Gynodioecy, the occurrence of females and hermaphrodites in
populations, is hypothesized as a common intermediate step in the
evolution of dioecy. In Schiedea, an endemic Hawaiian genus,
gynodioecious species with varying frequencies of females have
different patterns of resource allocation consistent with intermediate
steps in the evolution of dioecy. Species with higher frequencies of
females show greater differences in sex allocation patterns between
females and hermaphrodites than do species with lower female
frequencies. We examined the genetic potential for shifts in male and
female allocation in Schiedea salicaria (Caryophyllaceae), a
gynodioecious species with only 12% females. Using a partial diallel
design with 35 paternal half-sib families and 91 full sibships, we
estimated the additive genetic variance of male (stamen biomass) and
female (carpel + capsule biomass) allocation traits and their genetic
covariances with other reproductive characters. Both stamen biomass
and female biomass showed significant narrow-sense heritabilities. No
genetic correlations were detected between stamen biomass in
hermaphrodites and female biomass in either hermaphrodites (r =
-0.06, P = 0.71) or females (r = -0.12, P =
0.50), indicating that genetic correlations will not impede selection
for specialization in male or female function. The heritability of
these traits and patterns of genetic correlations suggest that S.
salicaria has the genetic potential to evolve greater sexual
dimorphism.
Key words: dioecy, gynodioecy, quantitative genetics, Schiedea, sex allocation