Diversification in the Arctic: Biogeography and Systematics of the North American Micranthes (Saxifragaceae)

Abstract—

Flora endemic to the cold habitats of the Northern Hemisphere provide important models for investigating diversification and disjunctions, given both the intense climatic fluctuations of these areas in the recent past and the fascinating biogeographic patterns of today’s Arctic-alpine plant communities. Micranthes Haw. (Saxifragaceae), a clade of small-flowered herbaceous flowering plants comprising ∼80 species, is an ideal group for investigating the evolution and diversification of plants in montane and Arctic ecosystems. Micranthes has proven to be a particularly challenging clade to unravel taxonomically due in part to rampant auto- and allopolyploidy, hybridization, and cryptic speciation. With the goal of providing an updated conspectus for this group, we build upon a recent large phylogenomic analysis to help elucidate the evolution of Micranthes. Here, we present new downstream analyses including diversification analyses, biogeographical reconstructions, and a comparison of methods for dating phylogenomic data sets. To complement these new analyses, we also synthesize chromosomal variation, new observations regarding morphology and species identification, comprehensive field studies, and an extensive review of the literature for Saxifragaceae and Micranthes. A new perspective on the systematics and taxonomy of Micranthes is provided.