Meeting Abstract
Organisms are more than the sum of their parts, making the study of complex integrated phenotypes imperative for understanding the interplay between the evolution of traits and the evolution of species. Molecular trait complexity is particularly important in species interactions, where more diverse networks of species interactions may select for molecular complexity in offensive or defensive traits, such as secreted toxins. Animal venoms, as injected secretions with a tractable genetic basis, are optimal systems for testing the hypothesis that the evolution of more complex molecular traits is associated with interacting with diverse prey taxa. The rattlesnakes (Crotalus and Sistrurus) are the most speciose group of vipers, consisting of ~50 currently described species. We have collected venom glands of 147 individuals snakes, representing most rattlesnake lineages. We use over 1500 nontoxin sequences from venom gland transcriptomes to infer the phylogeny of rattlesnakes, and characterize the composition and complexity of toxin expression in the transcriptomes and in chromatographic profiles of whole venom. We combine a novel, dated phylogeny of rattlesnakes, venom gene expression data, and published diet data to test the hypothesis that more complex venoms evolve in response to a more taxonomically complex diet. Our work provides new insight into the evolutionary history of this complex and iconic group, and relates complexity in patterns of gene expression to the complexity of ecological interactions an organism must face.
