Re-evaluation of taxonomic utility of male phallic complex in higher-level classification of Acridomorpha (Orthoptera: Caelifera). Insect Syst

The current higher classification of the orthopteran superfamily group Acridomorpha is largely based on interpretation of male phallic structures. Internal male genitalia have been considered as an excellent taxonomic character because of a widespread belief that they are less subject to selective pressures from environment, and thus more stable than external characters. Furthermore, based on a notion that evolu-tion proceeds from simple to complex, early taxonomists who shaped the higher classification of Acridomorpha considered those groups with less differentiated and membranous phallic structures as primitive and used this notion to deduce a phylogeny of Acridomorpha. In this study, we test these ideas based on a cladistic analysis of male phallic structures and a character optimization analysis to assess the level of homoplasy and synapomorphy for those phallic characters that have been traditionally used for the Acridomorpha systematics. We also perform an independent test of the phylogenetic utility of male phal-lic structures based on a molecular phylogeny. We show that while some phallic structures have strong phylogenetic signal, many traditionally used characters are highly homoplasious. However, even those homoplasious characters are often informative in inferring relationships. Finally, we argue that the notion that evolution proceeds in increasing complexity is largely unfounded and difficult to quantify in the higher-level classification of Acridomorpha