Geographic influence on genetic structure in the widespread Neotropical tree, Simarouba amara (Simaroubaceae)

Abstract

This study aimed to assess the population genetic structure of a widespread Neotropical tree species, Simarouba amara, at local, regional and continental spatial scales. We used five microsatellite loci to examine genetic variation in 14 natural populations (N=478 individuals) of this vertebrate dispersed rain forest tree species in Panama, Ecuador, and French Guiana. Estimates of genetic differentiation (Fst and Rst) were significant among all but one population pair and global differentiation was moderate (Fst=0.25, Rst=0.33) with 94% of genetic variation ascribed to differences among three main geographic regions (Central America, Western Ecuador, Amazon basin). There was no evidence of isolation by distance within regions. Allele-size mutations contributed significantly (RST > FST) to the divergences between cis and trans-Andean populations, highlighting the role of the northern Andean cordilleras as an important geographic barrier for this species.