Phylogenetics of Scorpions of Medical Importance

Abstract

This chapter assesses the phylogenetic relationships between scorpions and sodium channel-active scorpion toxins (NaScTx) of medical significance, almost entirely contained within the family Buthidae, with the exception of Hemiscorpius lepturus (Hemiscorpiidae). Within Buthidae, venom capable of severe and lethal scorpionism appears to have evolved multiple times among and within major morphological groups. Published mitochondrial sequence data from two markers (COI & 16S) were used to construct a partial maximum likelihood phylogeny for Buthidae. The resulting topology is largely congruent with results from comparative analysis of morphological data. Old World and NewWorld buthids appear to be split, suggesting that some ofthe higher-level patterns in Buthidae can be explained by the breakup of Pangea. Provided that the venom compo- sition should be more similar among closely related than distant species, the phylogeny can be used to predict which of the less dangerous species could also produce potent venoms. Clinical, phylogenetic, and toxinological evidence were also used to interpret the evolution and biogeography of these medically significant venomous taxa and the evolution of their toxic molecules. The existence of species-specific NaScTx repertoires in scorpions is probably the consequence of coevolution and arms races at the molecular and biochemical levels to overcome the ever-evolving structure of receptor sites (including sodium channels) in their predators and preys