Could venom variation be the main mechanism shaping snake distribution on Brazilian islands?
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The molecular mechanisms of adaptive evolution are unclear. We still do not have a complete understanding of how complex evolutionary novelties are generated during the process of recent speciation. Venomous snakes isolated on islands are considered a powerful model to study the evolutionary processes that create the phenotypic diversity. The venom diversity of the Bothrops jararaca species-complex has been suggested to be strongly related with the species diets and geography. Populations of B. jararaca underwent several episodes of recent speciation on the continental island off the southeastern coast of Brazil due to changes in the sea level during the end of the Pleistocene and the middle Holocene. This repeated speciation process, from the same ancestral population, makes this species-complex an extreme case of repeated recent adaptation to distinct niches. In this study we evaluated whether the variability of venom of the B. jararaca complex on islands and in the mainland can shed light on the evolutionary forces and mechanisms that shaped the colonization process in this group. We generated venom profiles, as well as, we sequenced different venom genes, the complete mitochondrial genome and anonymous loci for populations from the islands and the continent. We analyzed the genetic variability, inferred the demographic history, estimated divergence times and evolutionary rates, we also compared venom genes with other presumably neutral loci. Using population genetic tools, we aimed to test the hypothesis of rapid venom diversification being driven by ecological speciation by adaptive evolution to different diets, or alternately, if the demographic history can explain the venom differences among populations through genetic drift. We also expect to understand if the high toxin variability of B. jararaca venom represents the key factor that allows this group to successfully colonize several islands on the coast of Brazil.
Grazziotin FG. Could venom variation be the main mechanism shaping snake distribution on Brazilian islands?. Toxicon. 2019 Oct;168(suppl 1):2. doi:10.1016/j.toxicon.2019.06.028.
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