The family Saxifragaceae, the current composition of which is one of the great surprises of molecular systematics, has been subject to massive improvements in the knowledge of phylogenetic relationships. Nevertheless, developments from phylogenomic efforts have yet to be mobilized to inform biogeography and taxonomy. Here, we use a recent order-level phylogeny for Saxifragaceae and related families covering 72% of species with a set of new analyses to assess habitat evolution and biogeography. Our results suggest a North American origin of the family in cold alpine habitats, followed by rapid recent evolution of diverse habitat tolerances. We also combine these recent phylogenomic results and a synthesis of the literature to improve generic limits and tribal classification of Saxifragaceae. We recognize 40 genera in 10 tribes, with 14 new combinations, and elevate one subtribe as well as describing four new taxa at the tribal level. Finally, we synthesize information about biogeography and morphology for the family.

No abstract

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 ultimately 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.

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.

Abstract— Here I describe a new species, Heuchera folkii, narrowly endemic to high altitude limestone outcrops of the Sierra Madre Oriental, Coahuila, Mexico, together with a phylogenomic and morphometric evaluation of the Heuchera species of northeastern Mexico. Originally thought to be a disjunct population of Heuchera sanguinea, the new species is phylogenetically and morphologically most similar to Heuchera lakelae, from which it is distinguished based on morphometric characters and other morphological attributes, phylogenetic placement, geographic range, phenology, and ecological preferences.