Phylogeography of Brazilian pine (Araucaria angustifolia): integrative evidence for pre-Columbian anthropogenic dispersal

Abstract

Phylogeographic studies allow us to better understand the past history of species and the factors that mold their current distribution. Here, we demonstrate the potential human impact on the distribution of a tree species. In particular, it was hypothesized that Araucaria angustifolia, an endangered South American conifer, was dispersed from its Pleistocene glacial refugium to its maximum occurrence distribution (MOD), mainly by pre-Columbian human groups (ca 2000 years ago). In order to test this hypothesis, we sampled 20 A. angustifolia populations in southern Brazil. Our analysis consisted of an integrative phylogeographic approach, supported by ecological aspects of the species. Therefore, we constructed the species chloroplast haplotype network, tested for possible neutrality deviations, genetic divergence, association between genetic and geographic distances, and simulated the amount of time that the species required to reach its MOD without human help. The species showed clear signs of rapid and recent expansion from a single refugium. The haplotype network had a star-like shape. Populations and the species showed negative values for the neutrality tests and low divergence values among populations (FST = 0.041) not associated with geographic distance. The estimated dispersal time required for the species to reach its MOD from its putative refugium without human help is not consistent with the rapid and recent expansion of the species. Hence, we argue that humans played an important role in expanding the distribution of the currently endangered species, and it needs to be accounted for when analyzing landscape genetics or in the development of conservation strategies.