Evolution of Adaptive Variation at the Molecular Level: Snake Venom Proteins
Snake venom proteins represent a fascinating system for studies of molecular variation at the molecular level because proteomic and genomic analysis have shown high levels of variation in diverse species yet the evolutionary and functional basis of this variation remains unclear. Using venom proteins from rattlesnakes (Sistrurus and Crotalus) and lance-headed vipers (Bothrops) as a model system, we are addressing a series of questions about the evolutionary basis for inter- and intraspecific variation in venom proteins in relation to snake diets. These include: 1) How do venom proteins vary within and between species? 2) What is the functional significance of this variation in terms of toxicity to specific prey? 3) How do the genes encoding these proteins vary within and between species and what role has natural selection at the molecular level played in molding this variation? 4) What is relative importance of gene regulation vs. structural variation in proteins as a cause of variation in venom composition within and between species? We are addressing these questions through a combination of field work on wild snake populations, lab work on the genetic basis of venom variation, functional analysis of venom toxicity and proteomic analyses of venom composition. Recently, we have also become interested in the molecular bases for coevolutionary interactions between Pacific rattlesnakes and California ground squirrels as part of Matt Holding’s PhD project. Finally, our NSF-FAPESP grant is using a broad sampling of venomous snakes from the New World to address two major questions about venom evolution: First, is there a relationship between venom function and species level diversification rates? Two, are the molecular mechanisms by which differences in venom are generated are the same or different across species? Current collaborators on this research include Juan Calvete (Instituto Biomedicina de Valencia), Terry Farrell (Stetson University), Darin Rokyta (Florida State University), Chris Parkinson (University of Central Florida), Ana Moura, Inacio Azevedo and Erika Hingst-Zaher (Instituto Butantan), Hussan Zaher (USP) and Jim Biardi (Fairfield University).
Conservation Genetics of Endangered Species
Genetic analyses can guide the conservation and management of wildlife species by providing information on how demographically ‘connected’ and genetically variable populations are in space and time, by identifying genetically distinct populations and/or taxa of special conservation concern, and through the use of genes as biological “tags” for sourcing harvested individuals. One taxon of particular interest is the Eastern Massasauga Rattlesnake (Sistrurus c. catenatus); with support from the Ohio Division of Wildlife, we have conducted state- and range-wide assessments of genetic diversity within this taxon. We are also currently assessing levels of adaptive genetic variation in venom genes to assess the impact of declining population size on functional genetic variation.