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.
Highlights
The Atlantic Forest has remarkable biological diversity and a variety of vegetation types, including montane grassland, mangrove, restinga, tropical forest and subtropical forest, within a single Brazilian biome
20 haplotypes were identified (Table 1 and Supplementary File 1). The distribution of these haplotypes corroborates previously suggested partitioning of A. angustifolia populations in three genetic groups based on nuclear SSR markers[10]
These three groups are replicated in the distribution of the plastid haplotypes, in the spatial analysis of molecular variance (SAMOVA) analysis and in the Bayesian phylogenetic inference
Summary
The Atlantic Forest has remarkable biological diversity and a variety of vegetation types, including montane grassland, mangrove, restinga, tropical forest and subtropical forest, within a single Brazilian biome. Is a long-lived dioecious conifer species endemic to the subtropical Atlantic Forest in the highlands of Brazil and small patches of forest in Argentina[15] and Paraguay[16] This species presents a latitudinal discontinuous distribution with a large gap dividing the occurrence area of the species in two main geographical zones in Brazil: (i) a northernmost zone that is formed by scattered medium to large forest formations at high altitudes in the Southeastern region of the country and (ii) a southernmost zone, which is composed by a much wider area originally formed by large continuous forest formations in the Southern region of Brazil. Since these studies are based only on data from southernmost populations, without inclusion of samples representing the northern genetic group and weakly representing the most central populations in the Paraná State, those hypotheses were not tested
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