Molecular Phylogenetics and Historical Biogeography of Subtribe Ecliptinae (Asteraceae, Heliantheae)

We present a molecular phylogeny for the subtribe Ecliptinae (Asteraceae, Heliantheae) based on three plastid (matK, psbA-trnH, and trnQ-rps16) and two nuclear (nrITS and nrETS) markers. The results of the phylogenetic reconstruction were utilised as a topological constraint for a subsequent divergence dating analysis and ancestral range reconstructions. We sampled 41 species and 40 genera (72%) of Ecliptinae and two species of Montanoa (as outgroups) to elucidate the generic relationships between the genera of this subtribe. The Bayesian inference (BI) and Maximum Likelihood (ML) analyses were performed for the combined molecular dataset. The divergence dating analysis was performed using a relaxed, uncorrelated molecular clock with BEAST v1.8.4 and calibrated using a single secondary calibration point from a recently published chronogram for the family. The ancestral range reconstructions focusing on continents (i.e., South America, North America, Africa, Asia, and Oceania) and biomes (Dry forests, Altitudinal grasslands, Savannas, and Rainforests) were performed on BioGeoBEARS. Our phylogenetic results indicate that the genera of Ecliptinae are grouped into five clades, informally named the Monactis, Oblivia, Blainvillea, Wedelia, and Melanthera clades. The most recent, common ancestor of Ecliptinae was widespread in the North and South American dry forests at 8.16 Ma and mainly radiated in these regions up to the Pleistocene. At least eight dispersal events to South America and four dispersal events from North America to Africa, Asia, and Oceania took place during this period in all five informal clades of Ecliptinae. At least 13 biome shifts from dry forests to rainforests were evidenced, in addition to ten biome shifts from dry forests to altitudinal grasslands and savannas. These results corroborate the mid-late Miocene to early Pleistocene radiation of Ecliptinae in tropical dry forests. Future studies should aim to sample the remaining 14 unsampled genera of Ecliptinae to position them in one of the five informal clades proposed in this study.