Shifts in diversification rates linked to biogeographic movement into new areas, an example of disparate continental distributions and a recent radiation in the Andes

Abstract

AcknowledgementsWe would like to thank S. Mathews for kindly sharing genomic DNA for some taxa used in this study. J. Sullivan, L. Harmon, E. Roalson, J. Beaulieu, B. Moore, N. Nurk, M. Pennell, T. Peterson, and two anonymous reviewers for helpful suggestions or comments on the manuscript. J. Beaulieu, L. Harmon, C. Blair and the University of Idaho Institute for Bioinformatics and Evolutionary Studies (NIH/NCRR P20RR16448 and P20RR016454) for computational aid. Funding for this work was provided by NSF DEB-1210895 to DCT for SUC, NSF DEB-1253463 to DCT, and Graduate Student Research Grants to SUC from the Botanical Society of America (BSA), the Society of Systematic Biologists (SSB), the American Society of Plant Taxonomists (ASPT), and the University of Idaho Stillinger Herbarium Expedition Funds.\n\nPremise of the studyClade specific bursts in diversification are often associated with the evolution of key innovations. However, in groups with no obvious morphological innovations, observed upticks in diversification rates have also been attributed to the colonization of a new geographic environment. In this study, we explore the systematics, diversification dynamics, and historical biogeography of the plant clade Rhinantheae in the Orobanchaceae, with a special focus on the Andean clade of the genus Bartsia L..\n\nMethodsWe sampled taxa from across Rhinantheae, including a representative sample of Andean Bartsia species. Using standard phylogenetic methods, we reconstructed evolutionary relationships, inferred divergence times among the clades of Rhinantheae, elucidated their biogeographic history, and investigated diversification dynamics.\n\nKey resultsWe confirmed that the South American Bartsia species form a highly supported monophyletic group. The median crown age of Rhinantheae was determined to be ca. 30 Ma, and Europe played an important role in the biogeographic history of the lineages. South America was first reconstructed in the biogeographic analyses around 9 Ma, and with a median age of 2.59 Ma, this clade shows a significant uptick in diversification.\n\nConclusionsIncreased net diversification of the South American clade corresponds with biogeographic movement into the New World. This happened at a time when the Andes were reaching the necessary elevation to host an alpine environment. Although a specific route could not be identified with certainty, we provide plausible hypotheses to how the group colonized the New World.