Taxonomic utility of female copulation organs in Sericini chafers (Coleoptera, Scarabaeidae), with special reference to asymmetry

Abstract

Female genitalia are widely underrepresented in taxonomic studies. Here we investigate the morphological variation among female copulation organs for a group of scarab beetles (Sericini) with similar ecology, external morphology and copulation mechanics. We examined traits qualitatively and quantitatively based on 80 and 18 species (genus Pleophylla), respectively. Additionally we explored whether female genitalia are affected by asymmetry. The vast diversity of slerotised structures including their shapes illustrated the high taxonomic and phylogenetic utility of female genitalia in this group. The morphometric analysis of Pleophylla, confirmed that sclerotisations in the ductus bursae are very suitable for species-level taxonomic purposes. Stable interspecific variation is more hardly discernable in other parts such as the vaginal palps (shape and size) or the other membranous structures such as the shape of the bursa copulatrix. Asymmetric genitalia that arose multiple times independently among insects are found in most of the examined Sericini species. Asymmetries regarded either the bursa copulatrix, or both the bursa copulatrix and ductus bursae and comprised sclerotised and non-sclerotised structures being most common in modern Sericini. Here, highly asymmetric sclerotised structures are linked with strong asymmetry of the male copulation organs. Widespread asymmetry among megadiverse Sericini with a complex male-female genital asymmetry suggests that the shift to asymmetry is phylogenetically rather conserved. From the range of hypotheses, sexual selection seems to be the most reasonable to explain the evolution and stability of asymmetry in chafer genitalia.

Female genitalia are moderately informative for phylogenetic inference and not concerted with male genitalia in Saprininae beetles (Coleoptera: Histeridae)

“…In contrast to this, other studies report high informativeness of female genitalia for phylogenetic reconstruction (e.g. Özgül‐Siemund & Ahrens, ). This discordance of the results can be explained by differences in the selective regimes operating across different taxa.…”

“…However, as any evidence of correlation has not been found in the current study, we conclude that female and male genitalia are not correlated in the Saprininae. Interestingly, both patterns – the correlated (Özgül‐Siemund & Ahrens, ; Cayetano et al . , ) and independent (Polihronakis et al .…”

“…However, as any evidence of correlation has not been found in the current study, we conclude that female and male genitalia are not correlated in the Saprininae. Interestingly, both patterns -the correlated (Özgül-Siemund & Ahrens, 2015;Cayetano et al, 2011) and independent (Polihronakis et al, 2016) evolution of male-female genitalia -have been found in insects. The common driving force of the correlated evolution between male and female genitalia consists of sexual conflict, female choice and lock-and-key mechanism (Cordero-Rivera, 2017).…”

Taxonomic review of theDichotomius mamillatusgroup (Coleoptera: Scarabaeidae), with a description of a new species,Dichotomius(Dichotomius)gandiniisp. nov., from western Amazonia

“…Despite that, over the years, a significant number of researchers have considered the study of the female genitalia to be particularly informative for their taxonomic and phylogenetic investigations. Özgül‐Siemund & Ahrens () demonstrated that female genitalia, besides bearing highly valuable taxonomic characters, play a critical role in the investigation of the evolution of Sericini chafers. Lackner & Tarasov () suggested that the evolution of female genital characters in Saprininae clown beetles may have been driven by both natural and sexual selection.…”

“…These authors have found that the female genitalic system is more informative for supporting the phylogeny of some Saprininae clades, but generally, the informativeness of the male genitalia and exoskeletal characters was higher. Nonetheless, both Özgül‐Siemund & Ahrens () and Lackner & Tarasov () emphasised the potential of using female genitalia characters in taxonomy and systematics, but more investigations are needed to understand their usefulness.…”