Phylogeography of plastid DNA sequences suggests post-glacial southward demographic expansion and the existence of several glacial refugia for Araucaria angustifolia

Abstract

Despite the high diversity of the Southern South American environments, the patterns and processes driving both their species diversity and demographic history are still poorly known and are a challenging task. In this study, we evaluate plastid DNA sequences of the conifer species Araucaria angustifolia aiming to (i) assess the species genetic structure within its main range of occurrence, (ii) infer its population demographic history, looking for evidence of southward expansion, (iii) search for evidence of glacial refugia within the species distribution area and (iv) discuss some conservation and management strategies for this species. Twenty haplotypes were identified, revealing the presence of three distinct genetic groups across the geographic range of the species and structuring the populations into Northern, Central and Southern groups. Our results suggest the occurrence of post-glacial expansion of A. angustifolia towards the south, as well as the existence of at least three refugia within the species occurrence area. Testing the occurrence of historical demographic expansion, we suggest that genetic groups experienced fluctuations in effective size, associated to a structured distribution of populations. The identification of three genetic groups in this study corroborates the proposition of using the geographic distribution of A. angustifolia for selecting in situ conservation areas, for planning seed collection for ex situ conservation, as well as for the delineation of seed zones.