| Understanding the history of diversification in the North American deserts has long been a goal of biogeographers and evolutionary biologists. While it seems that a consensus is forming regarding the patterns of diversification in the Nearctic deserts in vertebrate taxa, little work has been done exploring the historical biogeography of widespread invertebrate taxa. Before a robust model of geobiotic change in the North American deserts can be proposed, it needs to be determined if the same historical events affected vertebrate and invertebrate taxa in the same way. I explored the phylogeographic patterns in four groups of widespread nocturnal velvet ants using two rDNA loci, the internal transcribed spacer regions 1 and 2 (ITS1 and ITS2). I used Bayesian phylogenetic analyses and haplotype network analyses to determine if a consistent geographic pattern exists among species and populations within each group. I also used molecular dating techniques to estimate divergence dates for each of the major phylogenetic clades. These analyses indicate that the species-level divergences in some groups occurred in the Neogene, and likely were driven by mountain building during Miocene-Pliocene times (~5 Ma) similar to the divergences in many vertebrate taxa, while species-level divergence in other groups occurred during the Pleistocene (1.8-0.1 Ma) and were likely driven by climatic oscillations and range contractions and expansion. Several recent studies have suggested that Neogene mountain-building events were more important to the development of a diverse desert-adapted biota. My research suggests, however, that both Neogene events and Pleistocene climatic changes were influential in the development of a species-rich nocturnal velvet ant fauna. |
