XVI International Botanical Congess
Pollen immigration and equivalent relative gamete production may retard loss of heterozygosity and offset negative effects of genetic drift on the future genetic composition of small, extinction-prone populations. Through allozyme analyses, we examined levels of genetic diversity, mating system, pollen immigration (m), and effective population sizes (Ne) in six small (N=3-35), spatially isolated populations of E. cyclocarpum in NW Costa Rica. Moderate levels of genetic diversity and high outcrossing rate estimates suggest inbreeding is not a problem. Pollen immigration is substantial and the fairly equivalent gamete production produced only moderate reduction in Ne relative to census population sizes. Direct estimates of m and Ne allowed us to predict moderate effects of genetic drift on the probability of fixation in future populations.