Abstract
Few studies have addressed the phylogeography of species of the Cerrado, the largest savanna biome of South America. Here we aimed to investigate the phylogeographical structure of Dalbergia miscolobium, a widespread tree from the Cerrado, and to verify its concordance with plant phylogeographical and biogeographical patterns so far described. A total of 287 individuals from 32 populations were analyzed by sequencing the trnL intron of the chloroplast DNA and the internal transcribed spacer of the nuclear ribosomal DNA. Analysis of population structure and tests of population expansion were performed and the time of divergence of haplotypes was estimated. Twelve and 27 haplotypes were identified in the cpDNA and nrDNA data, respectively. The star-like network configuration and the mismatch distributions indicated a recent spatial and demographic expansion of the species. Consistent with previous tree phylogeographical studies of Cerrado trees, the cpDNA also suggested a recent expansion towards the southern Cerrado. The diversity of D. miscolobium was widespread but high levels of genetic diversity were found in the Central Eastern and in the southern portion of Central Western Cerrado. The combined analysis of cpDNA and nrDNA supported a phylogeographic structure into seven groups. The phylogeographical pattern showed many concordances with biogeographical and phylogeographical studies in the Cerrado, mainly with the Cerrado phytogeographic provinces superimposed to our sampling area. The data reinforced the uniqueness of Northeastern and Southeastern Cerrados and the differentiation between Eastern and Western Central Cerrados. The recent diversification of the species (estimated between the Pliocene and the Pleistocene) and the ‘genealogical concordances’ suggest that a shared and persistent pattern of species diversification might have been present in the Cerrado over time. This is the first time that an extensive ‘genealogical concordance’ between phylogeographic and phytogeographic patterns is shown for the Cerrado biome.
Highlights
Considerable advances have been made in disentangling biogeographical patterns across the globe, but the diversification of many biodiversity rich areas of the world remain poorly studied [1]
The Cerrado is typically found in dystrophic soils, often latosols, under a climate characterized by a marked dry season, whereas the Seasonally Dry Tropical Forests (SDTF) typically occur in areas with more fertile soils and longer dry seasons [2,3,4]
We aimed to answer the following questions: 1) is the phylogeographical structure of this wide range species congruent with the Cerrado biogeographical provinces proposed by Ratter et al [11]? Considering that the historical casual factors that contributed to determine the phytogeographical provinces of Cerrado may have contributed to the phylogeographical structure of D miscolobium we predicted some congruency between them; 2) in what extension is the phylogeographical structure of D. miscolobium similar to other Cerrado tree species studied so far? Based on previous studies [20,21,22] we predicted that the southern populations present lower genetic diversity than populations from central Cerrado, which in turn would present high diversity levels, consistent with a recent colonization of southernmost populations from more stable northernmost areas
Summary
Considerable advances have been made in disentangling biogeographical patterns across the globe, but the diversification of many biodiversity rich areas of the world remain poorly studied [1]. One such region is the Cerrado biome, a savanna vegetation that, together with the Seasonally Dry Tropical Forests (SDTF), covers a huge diagonal seasonally dry area in the interior of Eastern Tropical South America (ETSA) [1,2,3]. Its almost 1.8 million km of original area has been reduced by more than 50% in the last years [7], making the Cerrado one of the main global hotspots for biodiversity conservation [5]. Many details about the historical biogeography of the Cerrado biome are unresolved [4,8]
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