Abstract

The Prosopis genus (Mimosoideae, Leguminosae) constitutes an important genetic resource for arid and semiarid environments. Prosopis chilensis (Molina) Stuntz is a multipurpose species native to South America, which displays high phenotypic variability. In Chile, this species grows in the semiarid region, along river beds of the transverse valleys. We studied the genetic diversity and population genetic structure of P. chilensis across the three transverse valleys of the Coquimbo Region (29 degrees-32 degrees S) by analysing the genetic diversity of 182 individuals with four nuclear and one chloroplast microsatellite markers. Using a spatial principal component analysis (sPCA), we detected a clear hierarchical genetic structure. This analysis revealed the existence of seven distinct genetic clusters throughout the whole studied region. None of the genetic clusters detected overlapped between valleys. This suggests that the mountain ridges separating the three transverse valleys may have exerted a barrier effect. However, while significant, population differentiation was low and most of the genetic variation was found within clusters. These results suggest that high gene flow might be counteracting and blurring the effects of the structuring factors. This is the first study of genetic population of P. chilensis in Chile and the genetic data obtained may be valuable for the conservation of this vulnerable, multipurpose tree species.