Mating System Dynamics of Ocotea Tenera (lauraceae), a Gynodioecious Tropical Tree!

Progeny arrays of Ocotea tenera (Lauraceae), a gynodioecious tree endemic to Costa Rica, were electrophoretically surveyed for allozyme variation to estimate the outcrossing rate in the overall population and to test for differences in outcrossing rates between hermaphroditic and female trees. Multilocus outcrossing rate estimates across 3 yr indicated O. tenera predominantly outcrosses. However, significant heterogeneity in single-locus outcrossing rates was found among loci. Two loci (FeZ, Fe2) gave high outcrossing estimates, and a third locus (Gdh) gave much lower outcrossing estimates. Heterogeneity in Gdh pollen allele frequencies, consanguineous matings, and selection against homozygous zygote genotypes at the FeZ and Fe2 loci are factors contributing to the discrepancy in outcrossing rate estimates among loci. There were no differences in the mating systems of hermaphroditic and female trees, which suggests that factors beyond prevention of selffertilization may have also promoted the evolution of gynodioecy in O. tenera.