Diversity and genetic structure of four keystone trees species of the Colombian Dry Tropical Forest

The Dry Tropical Forest (DTF) is one of the most degraded ecosystems in Colombia requiring urgent actions for the conservation of remaining populations and restoration of degraded sites. Genetic diversity is a fundamental tool that can be used to identify priority areas for in situ conservation and to evaluate the quality of populations as seed sources for use in restoration projects. Here we present the results of a genetic characterization of 251 individuals of four key species of Colombian DTF using ISSR (Inter Simple Sequence Repeats) molecular markers: Bursera simaruba, Platymiscium pinnatum, Hura crepitans and Caesalpinia ebano. The most diverse populations of all four species were observed in the Caribbean region and in the Chicamocha Canyon. Moreover, B. simaruba and P. pinnatum showed high genetic diversity in populations from the Cauca river valley and the Tatacoa desert, respectively. Strong spatial genetic structure was found for all four species and we propose that the observed genetic divergence could be linked to historical transformations of the DTF during geological periods of the Pleistocene and the Holocene. Finally, we identified potential seed sources in each region for each species and stress the importance of the northern Caribbean region and the Chicamocha Canyon for harboring high and unique genetic diversity.