Biogeographic history of the threatened species Araucaria araucana (Molina) K. Koch and implications for conservation: A case study with organelle DNA markers

摘要

Fragmentation of the habitat due to glaciations, fires and human activities affected the distribution range of Araucaria araucana in southern South America. On the borders of the Argentinean Patagonian steppe, the species is restricted to isolated patches without natural regeneration. Our objective is to test the hypothesis that these populations are relicts of pre-Pleistocene origin. A total of 224 individuals from 16 populations were sampled. Twenty chloroplast microsatellites, 19 non-coding chloroplast DNA regions and eight mitochondrial DNA fragments were screened for polymorphisms. A low transferability rate of universal primers from Pinaceae and also a low variation were detected for this ancient species. Only one non-coding region of the chloroplast DNA showed polymorphism allowing the identification of five haplotypes. A low genetic differentiation (G_(ST) = 0. 11; G′_(ST) = 0. 267) and lack of geographic structure was found. Allelic richness was lower and genetic differentiation higher among the eastern isolated populations, suggesting a long lasting persistence. Conservation guidelines are given for these relictual populations, which are located outside the limits of the National Parks.