Past and present genetic structure of the tropical rainforest palm Astrocaryum mexicanum : effects of anthropogenic fragmentation

To assess whether fragmentation of the lowland rainforest of Los Tuxtlas natural reserve has altered the genetic structure of understory palm Astrocaryum mexicanum , we analyzed populations from undisturbed forest and forest fragments. The questions that this study addressed were: Has habitat fragmentation reduced gene flow and within-population genetic variation (allele loss)? Has this process, in turn, increased population genetic differentiation of populations in fragments? We expected that reduced population sizes and gene flow, in fragments, has increased the effects of genetic drift, thus affecting genetic structure. The design of the study allows control for pre-fragmentation genetic structure, a common criticism against fragmentation studies, and addresses this question for a community-level important palm tree species of the tropical rain forests of southern Mexico. We sampled two cohorts ( i.e. , pre- and post-fragmentation palms) in each of eight populations (thirty individuals per cohort or generation, and a separation of four to nine km between populations), one composed by adult palms (80–140 years old), and the other of seedlings