Multilocus analysis of Pinus halepensis MILL. from Spain Genetic diversity and clinal variation

Fifteen populations of Pinus halepensis from Spain were analysed employing 5 polymorphic loci by starch gel electrophoresis. A multilocus approach was used, in order to detect changes in the level of polymorphism and to reveal the pattern recolonization of the species in a North-South direction, leading to a loss of variability among the island and marginal populations. Fifteen populations of Pinus halepensis from Spain were analyzed employing 5 polymorphic loci by starch gel electrophoresis. A multilocus approach was used, in order to detect changes in the level of polymorphism and to reveal the pattern of variation of the species. The multilocus analyses show that large differences exist when island, inland and marginal populations are considered. These differences are quite high in terms of the effective number of genotypes, and in subpopulation differentiation. The multilocus differentiation is mainly caused by relations of allelic frequencies among populations, the most likely cause being that, by chance, alleles were associated differently in the refugia of the species. The population differentiation is large in comparison with that observed in other conifers (FST = 0.11; CFST = 0.17). The canonical variate corresponding to the largest differentiation among populations is positively correlated to the frequency of the most common allele of Mdh4 and Aco and negatively to the frequency of Hk and Pgm2. A clear pattern of variation related to latitude and longitude has been detected by the high correlation with the first canonical variate (r = -0.907 and r = -0.832 respectively). In conclusion, the clinal variation could be attributed to a recolonization of the species in a North-South direction, leading to a loss of variability among the island and marginal populations.