Fragmentación y expansión demográfica en las poblaciones mexicanas de Pinus ayacahuite var. Ayacahuite

Abstract

This study explores the phylogeographic structure and the demographic history of the Mexican populations of Pinus ayacahuite var. ayacahuite. Three chloroplast microsatellites were amplifi ed in 198 individuals from 14 populations. Twelve haplotypes were found and an average genetic diversity (He) of 0.705. Two maximally differentiated groups were determined with a spatial analysis of molecular variance. A significant correlation was detected between the genetic and geographic distances between these two groups, but not within them. A significant phylogeographic structure was found, produced by the existence of the two groups. Two demographic expansions were detected, the first in the entire species, the second only in the southernmost populations. Additionally, a nested clade analysis was performed to complement our observations. The results showed that the Tehuantepec Isthmus was a corridor for species of temperate affinities in a cold period in early Pleistocene, and later acted as a barrier.