Dissertation Research: Phylogeny, Biogeography, and Rates of Speciation in Valerianaceae (Dipsacales)

Yale University, New Haven CT

Investigators

Abstract

Evolutionary biologists and ecologists have long been fascinated by explosive radiations of species that exhibit tremendous morphological diversity and occupy a wide range of habitats. The flowering plant lineage Valerianaceae contains 300-350 species that have been placed in 14-17 genera, with nearly 200 of the species being endemic to South America. These species exhibit a striking range of floral and vegetative forms. It has been hypothesized that the South American species represent a recent radiation. The availability of fossils will allow us to explicitly test biogeographic hypotheses and investigate rates of speciation within this group. The goals of this study are: 1) to infer the phylogeny of Valerianaceae using several DNA sequence data sets, 2) to examine morphological character evolution, 3) to elucidate the biogeographic history of Valerianaceae, and 4) to assess rates of speciation, with an emphasis on the South American radiation. This will be the first phylogentic analysis of Valerianaceae to include a broad sample of species from each of the genera and will also provide an empirical application of several new methods for the study of rates of evolution and speciation. Specifically we will test the hypothesis that over 200 species of Valerianaceae have originated since the formation of the Isthmus of Panama some 3-6 million years ago. This project will compliment ongoing studies of other lineages of the Dipsacales and will enhance our understanding of Northern Hemisphere biogeography and the origin of the South American flora. While our main aim is to address questions of broad evolutionary significance, there is an element of urgency to this research from the standpoint of conservation. Specifically, the enormous diversity now found in the Andes of South America is threatened by human impacts on the high elevation "paramo" vegetation.