GENETIC DIVERSITY AND DIFFERENTIATION OF Pseudotsuga menziesii (Mirb.) Franco POPULATIONS IN MÉXICO

Abstract

Mexican populations of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] constitute valuable gene pools for conservation and breeding programs of this species. Genetic diversity and population divergence were estimated using 18 isozyme loci and samples from 11 natural Douglas-fir populations in México. Genetic diversity was high at the species level (83.3 % polymorphic loci and 2.9 alleles per locus), but low at the population level (28.3 % polymorphic loci and 1.52 alleles per locus), particularly for populations from central México. A high level of population differentiation was found (F_st = 0.298), indicating that each population shares only a small fraction of the genetic diversity within the species and that genetic drift might have an important role in shaping the structure of genetic diversity in these populations. Genetic distances among populations in the Sierra Madre Oriental were positively correlated with geographic distances (r = 0.849), but the association was not significant according to the Mantel test. Populations from northeastern México separated from all others, whereas population Mohinora from northwestern México, joined those from central México. These results emphasize the priority for in situ conservation of Douglas-fir populations in central México.