Evidence for divergent patterns of local selection driving venom variation in Mojave Rattlesnakes (Crotalus scutulatus)
Year: 2018
Type: article
Abstract: Snake venoms represent an enriched system for investigating the evolutionary processes that lead to complex and dynamic trophic adaptations. It has long been hypothesized that natural selection may drive geographic variation in venom composition, yet previous studies have lacked the population genetic context to examine these patterns. We leverage range-wide sampling of Mojave Rattlesnakes (Crotalus scutulatus) and use a combination of venom, morphological, phylogenetic, population genetic, and environmental data to characterize the striking dichotomy of neurotoxic (Type A) and hemorrhagic (Type B) venoms throughout the range of this species. We find that three of the four previously identified major lineages within C. scutulatus possess a combination of Type A, Type B, and a 'mixed' Type A + B venom phenotypes, and that fixation of the two main venom phenotypes occurs on a more fine geographic scale than previously appreciated. We also find that Type A + B individuals occur in regions of inferred introgression, and that this mixed phenotype is comparatively rare. Our results support strong directional local selection leading to fixation of alternative venom phenotypes on a fine geographic scale, and are inconsistent with balancing selection to maintain both phenotypes within a single population. Our comparisons to biotic and abiotic factors further indicate that venom phenotype correlates with fang morphology and climatic variables. We hypothesize that links to fang morphology may be indicative of co-evolution of venom and other trophic adaptations, and that climatic variables may be linked to prey distributions and/or physiology, which in turn impose selection pressures on snake venoms.
Source: Scientific Reports
Authors: Jason L. Strickland, Cara F. Smith, Andrew J. Mason, Drew R. Schield, Miguel Borja, Gamaliel Castañeda-Gaytán, Carol L. Spencer, Lydia L. Smith, Ann Trápaga, Nassima M. Bouzid, Gustavo Campillo-García, Oscar A. Flores-Villela, Daniel Antonio-Rangel, Stephen P. Mackessy, Todd A. Castoe, Darin R. Rokyta, Christopher L. Parkinson
Institutions: University of Central Florida, Clemson University, University of Northern Colorado, The University of Texas at Arlington, Universidad Juárez del Estado de Durango, Museum of Vertebrate Zoology, University of California, Berkeley, University of Washington, Burke Museum of Natural History and Culture, Universidad Nacional Autónoma de México, Instituto Politécnico Nacional, Florida State University
Language: English
Subfield: Genetics
Domain: Life Sciences
Open Access status: gold
Estimated APC paid: $2,690
Funders: National Science Foundation, Yale University, University of California Institute for Mexico and the United States, Clemson University, Southwestern Association of Naturalists, Arizona State University, University of Texas at Arlington, Prairie Biotic Research, Consejo Nacional de Ciencia y Tecnología
Awards: Collaborative Research: Dimensions US-BIOTA-Sao Paulo: Scales of biodiversity - Integrated studies of snake venom evolution and function across multiple levels of diversity, G1609525514, G1614435070, G2003075670, G2460139648, Systematics, introgression, and adaptation in Western Rattlesnakes: a model system for studying gene flow, selection, and speciation, DISSERTATION RESEARCH: Delineation of populations, species, and genomic adaptations across a widely distributed venomous snake species complex, Collaborative Research: Dimensions US-BIOTA-Sao Paulo: Scales of biodiversity - Integrated studies of snake venom evolution and function across multiple levels of diversity, Collaborative Research: ABI Development: Development and Application of Graphical User Interfaces for System Building and Analysis of Membrane Simulations, UCF COMPASS (Convincing Outstanding-Math-Potential Admits to Succeed in STEM), Collaborative Research: Dimensions US-BIOTA-Sao Paulo: Scales of biodiversity-Integrated studies of snake venom evolution and function across multiple levels of diversity
OpenAlex ID: W2902988884