Meeting Abstract
Scorpions represent an iconic lineage of arthropods historically renowned for their unique segmental architecture, ancient fossil record, and potency of their venom. Considered to exemplify morphological stasis, scorpions have paradoxically been shown to harbor the most genes among all Metazoa, with accompanying sub- or neofunctionalization of novel gene copies. Higher-level relationships of scorpions, based exclusively on morphology, remain virtually untested, and no multilocus molecular phylogeny has been deployed heretofore toward assessing the basal topology. We apply a phylogenomic assessment to resolve scorpion phylogeny, for the first time sampling extensive molecular sequence data from all superfamilies, and examining basal relationships with up to 5,025 genes. Analyses of concatenated supermatrices as well as species tree approaches converge upon a basal topology of scorpions, and unanimously support a single origin of katoikogenic development, a form of parental investment wherein embryos are nurtured by connections to the parent’s digestive system. All analyses reject the monophyly of every superfamily with multiple constituent families; several families are also found to be non-monophyletic. These results suggest disutility of the few morphological character systems that are not prone to stasis in resolving higher-level relationships. Intriguingly, relationships based on the largest and sparsest supermatrix recover a topology in greater accord with traditional systematics. However, we demonstrate that support for this alternative topology is derived from non-randomly distributed missing data in sparsely sampled genes. Our findings are advocative of wholesale reevaluation of scorpion relationships grounded in molecular sequence data.
