The disproportionate abundance of species in mountains is a striking and mysterious pattern in global biodiversity. This project will unravel the evolutionary history of one of the largest genera of flowering plants, the louseworts, whose 770 species are found in mountain ranges across the Northern Hemisphere, but are especially rich in the Hengduan Mountains of China, the Altai-Tienshan of Russia, and the Himalayas. Phylogenetic relationships of a global sample of species will be reconstructed using DNA sequences. This "family tree" will then be used as an historical framework to test hypotheses about evolution and biogeography using additional data. For example, louseworts exhibit spectacular diversity in their flowers, but are pollinated only by bumblebees. Does competition between co-occurring louseworts for pollinator services cause evolutionary divergence in flower form and accelerate the splitting of ancestral species into distinct descendants? Other questions pertain to geographic origins, such as: is the Hengduan region an evolutionary "cradle" that favors new species formation, or is it a "museum" that harbors immigrants from other regions? Finally, the phylogenetic tree will be used to construct a natural classification for the lousewort genus, with taxonomic names reflecting lineages with common ancestry.
This project will reconstruct a large, conspicuous, and enigmatic branch of flowering plants on the tree of life, and reveal historical patterns and evolutionary processes that have shaped the diversity and distributions of plant species across the Northern Hemisphere since the Miocene. Understanding these evolutionary dynamics is critical to conservation planning, e.g., to put future climate change in an historical context. The mountains where louseworts occur are particularly vulnerable to climate change, raising the imperative to document these species and their evolutionary heritage. The research will also shed light on the evolution of floral form and function, and its contribution to the tempo and mode by which plant species coexist and proliferate.