Spatio-temporal evolution of the catuaba clade in the Neotropics: morphological shifts correlate with habitat transitions

Abstract

Aim: The biotic assembly of one of the most species-rich savannas, the Brazilian Cerrado, has involved recruitment of lineages from several surrounding regions. However, we lack a clear understanding about the timing and pathways of biotic exchanges among these regions and about the role those interchanges had in the assembly of Neotropical biodiversity. We investigated the timing and routes of species movements between wet or seasonally dry habitats across Neotropical regions and assessed the potential for ecological adaptation by evaluating the habitat transitions correlated with morphological shifts. Location: Neotropics. Taxon: The plant genus Anemopaegma (Bignonieae, Bignoniaceae). Methods: We inferred a Bayesian molecular phylogeny of Anemopaegma using one nuclear and two chloroplast markers. We sampled more than 90% of the known species diversity of Anemopaegma, covering its full geographical range. We estimated divergence times using a Bayesian relaxed-clock approach and inferred ancestral ranges as well as shifts in habitat and morphological characters. Results: Phylogenetic analyses recovered seven main clades within Anemopaegma. The genus likely originated in Amazonia in the late Oligocene. Early-diverging lineages diversified in situ in Amazonia, particularly during the Miocene, with independent dispersal events to the Andes, Atlantic Forest and Cerrado. Shifts from seasonally dry forest to savanna habitats were correlated with shifts from liana to shrub and the loss of tendrils. Main Conclusions: The timing of diversification of major lineages within Anemopaegma is consistent with major geological and climatic events that occurred during the late Palaeogene and Neogene, such as the Andean uplift and the Middle Miocene Climatic Optimum. Movements across different regions within the Neotropics were relatively common but shifts between habitats were not. The correlation in the evolution of the shrubby habit, the loss of tendrils and the shifts from forest to savanna are consistent with a scenario of ecological adaptation.