Plant diversification in the Espinhaco Range: Insights from the biogeography of Minaria (Apocynaceae)

The Espinhaco Range, eastern Brazil, is a region with remarkable floristic diversity and endemism, which are mainly concentrated in the campo rupestre. Minaria (Apocynaceae) is a genus with 21 species, most of which are endemic to the Espinhaco Range. In the present study, we investigated the biogeography of Minaria as the basis for understanding the origin and maintenance of plant diversity and endemism in the campo rupestre of the Espinhaco Range. We assessed the ecological divergence between clades, reconstructed the historical biogeography and dated the phylogeny of Minaria based on plastid and nuclear DNA. According to our estimates, Minaria arose in the Espinhaco Range during the Neogene. Its distribution is postulated to have been driven by a trend toward long-term retraction, interrupted by a few episodes of expansion. Ecologically, Minaria species do not present any obvious innovations that could explain their diversification by adaptive radiation. Apparently, the higher-altitude rocky savannas in the Espinhaco Range have offered stable environments in which dry seasons and fire regimes are less intense than in savannas at lower altitudes. Isolated on rocky outcrops, lineages would be more likely to differentiate by non-adaptive radiation, which may result in high plant diversity and endemism.