Examining Venom Diversification through Comparative Venom Gland Transcriptomics of Palm-Pitvipers

Mason, Andrew

ajmason@clemson.edu

Department of Biological Sciences

Clemson University

Clemson, South Carolina, USA

Sasa, Mahmood Instituto Clodomiro Picado

Facultad de Microbiología Universidad de Costa Rica San José, Costa Rica

Rokyta, Darin

Department of Biological Science Florida State University Tallahassee, Florida, USA

Parkinson, Christopher

Department of Forestry and Environmental Conservation Clemson University

Clemson, South Carolina, USA

Identifying the evolutionary mechanisms generating diverse phenotypes is key to understanding the origins of biodiversity through speciation and adaptation. Pitviper venoms are composite phenotypes of 10-100 individual toxins, most of which are the product of single genes. This allows for each toxin’s protein phenotype to be linked to their genetic origins with relative ease, facilitating evolutionary inference. Venoms are often highly variable among species, as is seen in Middle American palm-pitvipers (Bothriechis spp), though patterns of interspecific venom evolution and toxin diversification have been difficult to discern. To examine venom evolution in palm-pitvipers we generated venom gland transcriptomes from each of the 11 species of Bothriechis. We examine these data in relation to the species phylogeny and biogeography and identified orthologous groups of toxins to infer relative frequencies of toxin gains/losses. Venoms compositions were highly variable among species at the toxin-family and transcript-specific levels. The apparent prevalence of species-specific toxins suggested that toxins genes gains and/or loss occur relatively frequently, though the identification of toxins conserved among nearly all lineages suggests a primary role of regulatory evolution in shaping venom phenotypes. These results have further demonstrated that venom evolution occurs through multiple molecular mechanisms, all of which must be considered for a thorough understanding of the evolution of complex phenotypes.