Systematics Section / ASPT
Egan, Ashley N. , Crandall, Keith A. .
Macroevolutionary Impactors of Diversification in North American Psoraleeae (Leguminosae).
TRIBE Psoraleeae is estimated as the second youngest crown clade in Leguminosae, with the monophyletic North American (NAm) clade estimated as 6.3 million years old. The tribe also exhibits substitution rates higher than most other clades. The hypothesis of a recent, rapid radiation in NAm Psoraleeae makes this group keenly suited to studies of diversification rate variation at the genus/species level and the macroevolutionary factors that may have influenced its radiation. NAm Psoraleeae includes 5 genera (45 species) existing in varied habitats with a skewed species distribution towards Pediomelum, suggesting a shift in diversification rate within the group, perhaps spurred by environmental change. This study investigates the diversification of NAm Psoraleeae with an emphasis on hypothesis testing in a phylogenetic framework. Bayesian mixed models employed on the Internal Transcribed Spacer (ITS) & single-copy waxy (GBSSI) nuclear regions and the MatK, TrnS/G, & TrnL/F chloroplast regions was used to estimate phylogenies. These phylogenies were used to estimate age of generic splits in the group, test the hypothesis of a diversification rate shift within NAm Psoraleeae, and test hypotheses of macroevolutionary factors including habitat/climate regime shifts and Quaternary climate fluxes, as impacting the diversification rate. SymmeTREE supports the hypothesis of a shift in diversification rate in NAm Psoraleeae while r8s estimated the age of the Psoralidium + Pediomelum clade at roughly 2.4 mya, placing this key clade within influence of Quaternary climate fluxes. Habitat/climate regime shifts from moist, warm climes to dry, hot climes show a significant deviation from expected conditions, suggesting these shifts may have influenced NAm Psoraleeae evolution. The impact of Quaternary climate fluxes on diversification of NAm Psoraleeae was addressed using Birth-Death Likelihood. The outcome of this study provides insight into the evolution of NAm Psoraleeae, providing possible explanatory power to the why behind its recent, rapid radiation.
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1 - Brigham Young University, Microbiology and Molecular Biology, 751 Widb, Provo, Utah, 84602, USA
2 - Brigham Young University, Department of Integrative Biology, 401 Widtsoe Building, Provo, Utah, 84602, USA
Quaternary Climate Fluxes
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 31st, 2006
Time: 4:15 PM