Phylogeography of Fouquieria splendens and related Fouquieria species: Evolutionary history of North American warm deserts from a botanical perspective

Ocotillo (Fouquieria splendens), is a common and widespread spiny shrub native to the Sonoran, Peninsular, and Chihuahuan deserts. Five other congeneric species of Fouquieria occupy more restricted areas of these regional deserts, often co-occurring with F. splendens. The combined distribution of F. splendens and related Fouquieria taxa throughout the Sonoran, Peninsular, and Chihuahuan deserts makes this endemic species complex an ideal exemplar for understanding the phylogeographic history of the core desert plants of southwestern North America. Modern phylogeographic studies of these regional deserts based on animal species have revealed cryptic species and unexpectedly ancient relationships among these regions. While deserts are typically defined on the basis of plant distributions, phylogeographic studies of wide-ranging, desert-adapted plant taxa are lacking. No study to date has examined the phylogeography of any plant taxon throughout the North American regional warm deserts. A combination of AFLP, nuclear, and chloroplast markers are being used to determine relationships among individuals and species of Fouquieria. Data from nuclear and chloroplast markers indicate complex relationships among Fouquieria species in the Sonoran and Peninsular Desert regions. Preliminary analysis of AFLP data shows divisions between spatially distant populations of F. splendens. This study will be among the first to compare patterns of evolutionary relationships among North American warm deserts with dispersal paths in a widespread, woody, arid-adapted plant species.