Molecular phylogeny informs generic and subgeneric concepts in the Schizoptera Fieber genus group (Heteroptera : Schizopteridae) and reveals multiple origins of female-specific elytra

Abstract

Wing dimorphism occurs in many genera of Schizopteridae Reuter, 1891 and other litter bugs (Heteroptera:Dipsocoromorpha), in both males and females. In the largest litter bug genus, Schizoptera Fieber, and closely related taxa, sexual wing dimorphism is observed in several species whereby males are macropterous, but females possess elytra, or hardened forewings – a feature that is rare outside of beetles and that we here refer to as female-specific elytra. Phylogenetic hypotheses for Schizoptera are unavailable, but are essential to reveal if female-specific elytra evolved once or multiple times within the genus and to test if the presence of elytra can reverse states to macropterous wings. In addition, generic and subgeneric concepts of this speciose genus-group have not been tested in a phylogenetic framework, and relationships with other schizopterid genera remain largely unknown. Our molecular phylogeny of Schizoptera and related genera documents that this genus is currently polyphyletic, and we raise the subgenus Kophaegis to generic rank to render Schizoptera monophyletic (Orthorhagus was recently elevated to genus). Relationships within Schizoptera reveal several well supported clades, some of them corresponding to currently recognised subgenera. To examine the value of previously used diagnostic features, we optimise 11 morphological characters on the molecular phylogeny and update generic and subgeneric diagnoses. Tracing transitions between macropterous and elytrous wing types, we show that female-specific elytra evolved at least seven times within Schizopteridae, four of those times within the Schizoptera genus-group, and that elytra reversed to macropterous wings at least twice. We propose that Schizopteridae may be an excellent model to study the selective pressures that have given rise to sexually dimorphic traits.