Mapping species richness and evolutionary regions of the genus Myrcia

Aim: Myrcia is a plant genus exclusive of the Neotropical region and one of the most important components of the tree diversity in the Cerrado and Atlantic Forest domains. However, no mapping of its taxonomic diversity for this region exists. Our aim was to describe the spatial patterns of diversity and biogeographical history for Myrcia in the Neotropical region based on a phylogenetic regionalization. Location: Neotropics. Taxon: Genus Myrcia (Myrtaceae). Methods: We derived distributions for 307 species from occurrence records using buffering and species distribution modelling. We used stacked distributions to generate a richness map of the genus and its clades (sections). In addition, we used phylogenetic regionalization methods to define evolutionary regions (evoregions) and ancestral area reconstruction to reveal the biogeographical history across these evoregions. Results: We found high species richness in the Atlantic Forest and Cerrado, with some sections restricted to the East coast of South America, while others were widespread across the Neotropics. We defined five evoregions, named A–E; the ancestral reconstruction revealed that Myrcia originated in evoregion B, under a tropical climate, with further specialization of distant-related lineages to the colder environmental condition in evoregion A. Main Conclusions: High species richness of Myrcia in South America eastern coast and in the Brazilian highlands coincides with the evoregions with most diversification. Our genus-specific regionalization together with the ancestral area reconstruction showed that evoregions A and B were the main evolutionary regions where diversification took place. In addition, the biogeographical history of the group suggests that some lineages have adaptations to deal with colder environments, that probably evolved in response to cooling periods since the mid-Miocene.