Venom evolution of South American advanced snakes: an integrated approach comparing cis-/trans-Andean lineages

Abstract

Advanced snakes (superfamily Colubroidea) constitute one of the most diverse groups of terrestrial vertebrates worldwide. It is comprised of more than 2,500 species and includes the front-fanged venomous families Viperidae (e.g., vipers) and Elapidae (e.g., coral snakes), and rear-fanged venomous species in the family Colubridae (e.g., colubrids). In the Neotropical region, where their diversity is the highest, some groups within this superfamily have become important organisms for exploring historical patterns of diversification and ecological processes that mold diversity in this region, but also the subject of significant toxinological research. The study of their venoms has been pivotal in the development of diagnostic assays and therapeutic drugs, and for the treatment of snakebite envenoming not only in Latin America but also in other regions of the world (e.g., sub-Saharan Africa). Although most of this research has been focused on pitvipers and coral snakes, in recent years it has been also recognized the need to study the poorly explored composition and function of toxins present in the highly diverse colubrid snakes.Even though great advancements have been made in the areas described above, one aspect remaining in the study of Neotropical advanced snakes is the evolution of lineages present in western South America (i.e., trans-Andean lineages), as opposed to those present on the eastern side of the Andes (i.e., cis-Andean lineages). We still lack a good understanding of their diversity, phylogenetic affinities with other groups of South American Colubroidea, and toxin diversity. Even in the most recent and comprehensive phylogenetic studies, some of these groups are usually poorly represented and/or present low to modest phylogenetic resolution. Moreover, in recent years, a more thorough exploration of the topographically complex Andes has revealed new species to science, even for well-studied groups such as pitvipers, and the discovery of evolutionary mechanisms for the origin and maintenance of their diversity. Certainly, a better integration between countries and investigators is needed to properly conduct such studies on cis-/trans-Andean lineages of South American advanced snakes. More information about this subject can be found in the document "Scientific Background" attached to this proposal.We propose to improve these knowledge gaps by strengthening a collaboration that started in 2017 between researchers from Instituto Butantan in Brazil and Universidad Tecnológica Indoamérica in Ecuador. We plan to do so by (1) exploring venom diversity and evolutionary relationships among basal lineages of bothropoid pitvipers that will complement our understanding of the evolution of Brazilian lineages of these snakes; (2) comparing evolutionary trends of toxin diversity using insular groups of advanced snakes present in the Galapagos archipelago and the islands off the coast of São Paulo; (3) interacting with snake specialists from Universidade de São Paulo to collaborate on studies exploring the relationships between venom and diet in the evolution of these animals; (4) offering a graduate-level course on evolutionary principles for understanding the diversity of venomous animals and their toxins; and (5) establishing the exchange of preserved specimens that are important for our natural history collections, but also promote future academic visits of students between our institutions.This collaboration will result in the addition of key samples from Andean and Galapagos advanced snakes to projects already funded by FAPESP (Thematic Project 2016/50127-5 e CEPID 2013/ 07467-1, among others). Moreover, the complementary expertise of researchers from both institutions will benefit the transdisciplinary nature of the projects by linking key areas of Instituto Butantan's mission in Latin America: venomous animals research, toxin study, and zoological collection maintenance. (AU)