Biogeographic breaks in the Atlantic Forest: evidence for Oligocene/Miocene diversification in Bertolonia (Melastomataceae)

Abstract

Abstract The distribution of major clades in Bertolonia (Melastomataceae) is congruent with subareas of the Atlantic Forest, providing an opportunity to estimate ages of historical breaks in the Atlantic Forest, from its major north/south split to more restricted local radiations. The role of niche conservatism in driving diversification of Bertolonia is also analysed and discussed in the light of its historical distribution. We estimated the age of the diversification events, gathered the climatic envelopes of species and clades, generated bioregions for the Atlantic Forest and reconstructed the ancestral areas of speciation for the genus. Our analysis subdivided the Atlantic Forest in five subareas, three of them in the northern and two in the southern Atlantic Forest. We also recovered a deep north/south divergence of the Atlantic Forest in the Oligocene (c. 30 Mya) followed by subsequent local radiations in both regions and a south-eastern/southern division in the Miocene. Later diversification happened mostly from the Mid-Miocene to Pliocene/Pleistocene with several dispersal events, mostly between neighbouring areas. We corroborated this assumption demonstrating that closely related lineages tend to occur in habitats with similar climatic conditions, mainly related to temperature. Our analyses on Bertolonia effectively captured relatively old historical events in the Atlantic Forest, such as the north/south division in the Oligocene and south/south-eastern split in the Miocene, but also recent ones, such as climatic fluctuations and forest fragmentation in the Quaternary. We indicate here for the first time that, for some organisms, the well-known north/south split of the Atlantic Forest could be older than expected. Recent radiation events occurred mainly on a regional basis after this deep division of the domain and the subclades that were recovered showed a significant climatic niche conservatism.