Gonna need more genomes: genomic implications of introgression in rattlesnakes

Myers, Ed

eamyers@clemson.edu

Rautsaw, Rhett

Parkinson, Chris

Department of Biological Sciences

Clemson University

Clemson, South Carolina USA

The evolutionary history of rattlesnakes has been notoriously difficult to estimate, with different datasets and methods of phylogeny reconstruction resulting in different topologies. Recent population genomic and small-scale phylogenetic studies have suggested that divergence with gene flow is common within this group. Whether gene flow and introgression among species has influenced past interpretations of phylogenetic relationships is not known. Here, we generate transcriptomic data for nearly all named species of rattlesnake (genera Crotalus and Sistrurus), generate a fossil calibrated phylogeny, and conduct genomic tests for introgression across this radiation. Introgression between species has led to a high degree of gene-tree discordance; this is likely the cause of disagreement between previously published phylogenies in the placement of several taxa (e.g., C. horridus and C. willardi). We discuss these results in the context of the consequences of hybridization and introgression in rattlesnakes and across the tree of life.