Does mate limitation in self-incompatible species promote the evolution of selfing? The case of Leavenworthia alabamica.

摘要: Genetic diversity at the S-locus controlling self-incompatibility (SI) is often high because of negative frequency-dependent selection. In species with highly patchy spatial distributions, genetic drift can overwhelm balancing selection and cause stochastic loss S-alleles. Natural may favor breakdown SI in populations few S-alleles low S-allele constrains seed production self-incompatible plants. We estimated diversity, effective population sizes, migration rates Leavenworthia alabamica, a mustard restricted to discrete habitat patches rocky glades. Patterns polymorphism were investigated S-Iocus 15 neutral microsatellites three large small 100-fold variation glade size. Populations on larger glades maintained more S-alleles, but all harbor least 20 mate availabilities typically exceeded 0.80, which consistent little limitation nature. Estimates size (N e ) each ranged from 600 1600, (m) 3 x 10 ―4 nearly 1 ―3 . According theoretical models, there limited opportunity for reduce these attributes. Although pollinators or resources limit glades, does not appear be factor promoting incipient this that studied.