Biogeography of Stigmaphyllon (Malpighiaceae) and a Meta-Analysis of Vascular Plant Lineages Diversified in the Brazilian Atlantic Rainforests Point to the Late Eocene Origins of This Megadiverse Biome

We investigated the biogeography of Stigmaphyllon, the second-largest lianescent genus of Malpighiaceae, as a model genus to reconstruct the age and biogeographic history of the Brazilian Atlantic Rainforest (BAF). Few studies to date have focused on the tertiary diversification of plant lineages in the BAFs, especially on Stigmaphyllon. Phylogenetic relationships for 24 species of Stigmaphyllon (18 ssp. From the Atlantic forest (out of 31 spp.), three spp. from the Amazon Rainforest, two spp. from the Caatinga biome, and a single species from the Cerrado biome) were inferred based on one nuclear DNA (PHYC) and two ribosomal DNA (ETS, ITS) regions using parsimony and Bayesian methods. A time-calibrated phylogenetic tree for ancestral area reconstructions was additionally generated, coupled with a meta-analysis of vascular plant lineages diversified in the BAFs. Our results show that: (1) Stigmaphyllon is monophyletic, but its subgenera are paraphyletic; (2) the most recent common ancestor of Stigmaphyllon originated in the Brazilian Atlantic Rainforest/Caatinga region in Northeastern Brazil ca. 26.0 Mya; (3) the genus colonized the Amazon Rainforest at two different times (ca. 22.0 and 6.0 Mya), the Caatinga biome at least four other times (ca. 14.0, 9.0, 7.0, and 1.0 Mya), the Cerrado biome a single time (ca. 15.0 Mya), and the Southern Atlantic Rainforests five times (from 26.0 to 9.0 Mya); (4) a history of at least seven expansion events connecting the Brazilian Atlantic Rainforest to other biomes from 26.0 to 9.0 Mya, and (5) a single dispersion event from South America to Southeastern Asia and Oceania at 22.0 Mya via Antarctica was proposed. Compared to a meta-analysis of time-calibrated phylogenies for 64 lineages of vascular plants diversified in the Brazilian Atlantic Rainforests, our results point to a late Eocene origin for this megadiverse biome.