Speciation in Western North America: Lomatium as an Example of Diversification and Convergent Evolution

Species delimitations and understanding the processes that drive speciation are essential to nearly all aspects of human endeavor. Determining species boundaries traditionally used morphology. Phylogenetic analyses based on DNA sequence data provide a means to resolve species boundaries, as well as test hypotheses regarding the evolutionary processes. Numerous species radiations have occurred in Western North America. Among these are several plant groups such as Astragalus, Artemisia, and Lomatium. Recent phylogenetic analyses of Lomatium and related genera have demonstrated that many of the morphological characters used to delimit taxa have arisen multiple times and that most taxa are para- or polyphyletic. Here we examine one of the clades recovered in the Lomatium group of taxa that includes Lomatium triternatum and L. grayi. The several subspecific taxa of L. triternatum have not been recovered as monophyletic and L. grayi has a widespread habitat distribution that may indicate cryptic speciation. Previous analyses have not fully resolved phylogenetic relationships with strong support. In the present study we sample an additional four loci (three chloroplast and one nuclear ribosomal) to improve the support for evolutionary relationships across this clade, resolve species boundaries, and test hypotheses on the evolution of morphological traits.