Speciation at the Mogollon Rim in the Arizona Mountain Kingsnake (Lampropeltis pyromelana).

Studies of speciation and taxon delimitation are usually decoupled. Combining these methods provides a stronger theoretical ground for recognizing new taxa and understanding processes of speciation. Using coalescent methods, we examine speciation, post-speciation population demographics, and taxon delimitation in the Arizona Mountain Kingsnake (Lampropeltis pyromelana), a species restricted to high elevations in southwestern United States and northern Mexico (SW). These methods provide a solid foundation for understanding how biogeographic barriers operate at the regional scale in the SW. Bayesian species delimitation methods, using three loci from samples of L. pyromelana taken throughout their range, show strong support for the existence of two species that are separated by low elevation habitats found between the Colorado Plateau/ Mogollon Rim and the Sierra Madre Occidental. Our results suggest an allopatric mode of speciation given the near absence of gene flow over time, which resulted in two lineages of unequal population sizes. Speciation likely occurred prior to the Pleistocene, during the aridification of the SW and/or the uplift of the Colorado Plateau, and while these species occupy similar high-elevation niches, they are isolated by xeric conditions found in the intervening low deserts. Furthermore, post-speciation demographics suggest that populations of both lineages were not negatively impacted by climate change throughout the Pleistocene. Finally, our results suggest that at least for this group, where divergence is old and gene flow is low, Bayesian species delimitation performs well.

Thousands of microsatellite loci from the venomous coralsnake Micrurus fulvius and variability of select loci across populations and related species.

Studies of population genetics increasingly use next-generation DNA sequencing to identify microsatellite loci in nonmodel organisms. There are, however, relatively few studies that validate the feasibility of transitioning from marker development to experimental application across populations and species. North American coralsnakes of the Micrurus fulvius species complex occur in the United States and Mexico, and little is known about their population structure and phylogenetic relationships. This absence of information and population genetics markers is particularly concerning because they are highly venomous and have important implications on human health. To alleviate this problem in coralsnakes, we investigated the feasibility of using 454 shotgun sequences for microsatellite marker development. First, a genomic shotgun library from a single individual was sequenced (approximately 7.74 megabases; 26,831 reads) to identify potentially amplifiable microsatellite loci (PALs). We then hierarchically sampled 76 individuals from throughout the geographic distribution of the species complex and examined whether PALs were amplifiable and polymorphic. Approximately half of the loci tested were readily amplifiable from all individuals, and 80% of the loci tested for variation were variable and thus informative as population genetic markers. To evaluate the repetitive landscape characteristics across multiple snakes, we also compared microsatellite content between the coralsnake and two other previously sampled snakes, the venomous copperhead (Agkistrodon contortrix) and Burmese python (Python molurus).