Format: ORAL

Ryan A. Folk1, Michelle L. Gaynor2,3, Nicholas J. Engle-Wrye1, Brian C. OMeara4, Pamela S. Soltis2,5, 6, Douglas E. Soltis2,3,5, 6, Robert P. Guralnick2, 6, Stephen A. Smith7, Charles J. Grady8, Yudai Okuyama9Ryan A. Folk1*, Michelle L. Gaynor2,3*, Nicholas J. Engle-Wrye1, Brian C. OMeara4, Pamela S. Soltis2,5, 6, Douglas E. Soltis2,3,5, 6, Robert P. Guralnick2, 6, Stephen A. Smith7, Charles J. Grady8, Yudai Okuyama9

1 Department of Biological Sciences, Mississippi State University, Mississippi State, MS, USA 2 Florida Museum of Natural History, University of Florida, Gainesville, FL, USA 3 Department of Biology, University of Florida, Gainesville, FL, USA 4 Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, USA 5 Genetics Institute, University of Florida, Gainesville, FL, USA 6 Biodiversity Institute, University of Florida, Gainesville, FL, USA 7 Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA 8 Biodiversity Institute, University of Kansas, Lawrence, KS, USA 9 Tsukuba Botanical Garden, National Museum of Nature and Science, Tsukuba, Japan

Applications of molecular phylogenetic approaches have uncovered evidence of hybridization across numerous clades of life, yet the environmental factors responsible for driving opportunities for hybridization remain obscure. Verbal models implicating geographic range shifts that brought species together during the Pleistocene have often been invoked, but quantitative tests using paleoclimatic data are needed to validate these models. Here, we produce a phylogeny for Heuchereae, a clade of 15 genera and 83 species in Saxifragaceae, with complete sampling of recognized species, using 277 nuclear loci and nearly complete chloroplast genomes. We then employ an improved framework with a coalescent simulation approach to test and confirm previous hybridization hypotheses and identify one new intergeneric hybridization event. Focusing on the North American distribution of Heuchereae, we introduce and implement a newly developed approach to reconstruct potential past distributions for ancestral lineages across all species in the clade and across a paleoclimatic record extending from the late Pliocene. Time calibration based on both nuclear and chloroplast trees recovers a mid- to late-Pleistocene date for most inferred hybridization events, a timeframe concomitant with repeated geographic range restriction into overlapping refugia. Our results indicate an important role for past episodes of climate change, and the contrasting responses of species with differing ecological strategies, in generating novel patterns of range contact among plant communities and therefore new opportunities for hybridization. The new ancestral niche method flexibly models the shape of niche while incorporating diverse sources of uncertainty and will be an important addition to the current comparative methods toolkit.