DOI: 10.5061/dryad.sr927n43
title: Data from: Divergence and diversification in North American Psoraleeae (Fabaceae) due to climate change

description: BACKGROUND: Past studies in the legume family (Fabaceae) have uncovered
 several evolutionary trends including differential mutation and
 diversification rates across varying taxonomic levels. The legume tribe
 Psoraleeae is shown herein to exemplify these trends at the generic and
 species levels. This group includes a sizable diversification within North
 America dated at approximately 6.3 million years ago with skewed species
 distribution to the most recently derived genus, Pediomelum, suggesting a
 diversification rate shift. We estimate divergence dates of North American
 (NAm) Psoraleeae using Bayesian MCMC sampling in BEAST based on eight DNA
 regions (ITS, waxy, matK, trnD-trnT, trnL-trnF, trnK, trnS-trnG, and
 rpoB-trnC). We also test the hypothesis of a diversification rate shift
 within NAm Psoraleeae using topological and temporal methods. We
 investigate the impact of climate change on diversification in this group
 by (1) testing the hypothesis that a shift from mesic to xeric habitats
 acted as a key innovation and (2) investigating diversification rate
 shifts along geologic time, discussing the impact of Quaternary climate
 oscillations on diversification. RESULTS: NAm Psoraleeae represents a
 recent, rapid radiation with several genera originating during the
 Pleistocene, 1 to 2 million years ago. A shift in diversification rate is
 supported by both methods with a 2.67-fold increase suggested around 2
 million years ago followed by a 8.73-fold decrease 440,000 years ago. The
 hypothesis that a climate regime shift from mesic to xeric habitats drove
 increased diversification in affected taxa was not supported. Timing of
 the diversification rate increase supports the hypothesis that
 glaciation-induced climate changes during the Quaternary influenced
 diversification of the group. Nonrandom spatial diversification also
 exists, with greater species richness in the American Southwest.
 CONCLUSION: This study outlines NAm Psoraleeae as a model example of a
 recent, rapid radiation. Diversification rate shifts in NAm Psoraleeae are
 not due to current climate regimes as represented by habitat, but instead
 to past global climate change resulting from Quaternary glaciations. NAm
 Psoraleeae diversification is a good example of how earthly dynamics
 including global climate change and topography work together to shape
 biodiversity.
description: Psoraleeae_Chronogram_Fig1Chronogram representing the maximum clade credibility tree estimated in BEAST based on total evidence across eight DNA regions using mixed models. Mean divergence dates shown for key nodes. Gray bars represent the 95% high posterior density credibility interval for node age. * nodes used as calibration points. Arrow denotes shift from/to mesic (m) or xeric (x) habitat hypothesized along the lineage shown. Ingroup: P = Pediomelum; Ps. = Psoralidium; R. = Rupertia; O. = Orbexilum; H. = Hoita. Outgroup: C. = Cullen; Ot. = Otholobium; B. = Bituminaria; G. = Glycine; Ph. = Phaseolus; D. = Desmodium. Numbers following taxon names represent accession numbers with reference to previous workBMCBiologytree.txt