Mitochondrial phylogeny and molecular-based species delimitation illuminate cryptic diversity in saw-scaled vipers (Viperidae: Echis)

Molecular species delimitation can clarify species limits and uncover morphologically cryptic taxa, particularly in groups that have conflicting taxonomies based on morphology alone. We reassess the phylogenetic relationships within Echis, a viperid genus widely distributed in the Eastern Hemisphere with a complicated taxonomic history. Using 134 mitochondrial cytb sequences sampled from ten of the twelve currently recognised species, we applied gene-tree and distance-based species delimitation methods to delineate evolutionary significant units within Echis. Our results validate current taxa, adding additional support to recently described species, and uncover cryptic genetic diversity within Echis. Although single-locus delimitation methods may not fully capture species diversity, congruent support between methods can identify lineages in need of future investigation. We emphasise that the lineages identified here can be used as a guide for further geographic sampling and in an integrative taxonomic treatment of Echis that combines genomics, morphometrics and ecological data in a unified framework.