Untangling the assassin's web: Phylogeny and classification of the spider-associated Emesine complex (Hemiptera: Reduviidae)

Abstract

Web-building spiders are formidable predators, yet assassin bugs in the Emesine Complex (Hemiptera: Reduviidae: Emesinae, Saicinae, and Visayanocorinae) prey on spiders. The Emesine Complex comprises >1000 species and these web-associated predatory strategies may have driven their diversification. However, lack of natural history data and a robust phylogenetic framework currently preclude tests of this hypothesis. We combine Sanger (207 taxa, 3865 bp) and high-throughput sequencing data (15 taxa, 381 loci) to generate the first taxon- and data-rich phylogeny for this group. We discover rampant paraphyly among subfamilies and tribes, necessitating revisions to the classification. We use ancestral character state reconstructions for 40 morphological characters to identify diagnostic features for a revised classification. Our new classification treats Saicinae Stål and Visayanocorinae Miller as junior synonyms of Emesinae Amyot and Serville, synonymizes the emesine tribes Ploiariolini Van Duzee and Metapterini Stål with Emesini Amyot and Serville, and recognises six tribes within Emesinae (Collartidini Wygodzinsky, Emesini, Leistarchini Stål, Oncerotrachelini trib.n., Saicini Stål stat.n., and Visayanocorini Miller stat.n.). We show that a pretarsal structure putatively involved in web-associated behaviours evolved in the last common ancestor of Emesini, the most species-rich clade within Emesinae, suggesting that web-associations could be widespread in Emesinae.