Congruence between comparative morphology and molecular phylogenies: Evolution of the male genital skeletal/muscular system in the subtribe Polyommatina (Lepidoptera, Lycaenidae)

Abstract

The skeleton and musculature of male genitalia were studied in species of a model butterfly group (subtribe Polyommatina, Lycaenidae). In total, we analyzed 45 species of the tribe Polyommatini most of which were previously used in the molecular phylogenetic study (Talavera et al., 2013). The studied morphological characters were mapped on the molecular trees, which allowed us to reveal trends of morphological changes and to estimate the age of their origin. As a result, chronology of evolution of skeleton and musculature traits was established. It was shown that periods of slow morphological evolution alternated in the subtribe Polyommatina with those of a high rate of origin of new traits. For example, topography of the intravalvar muscles has not changed for 26 MY preserving their initial fan-shaped attachment. The evolution of intravalvar muscles started 10 MYA, proceeded slowly during the first 5 MY, and then accelerated during the last 5 MY resulting in the extensive splitting of the musculature in most monophyletic lineages. Mapping the morphological characters on the phylogeny demonstrated that the rates of skeleton and muscle evolution within the skeleton/musculature apparatus were different. In most cases the intravalvar musculature evolved much faster than the skeleton. The cladistic interpretation of states of morphological traits was found to be consistent with phylogenetic reconstructions based on analysis of multiple molecular markers. Moreover, morphological synapomorphies were found for the lineages Alpherakya + Glabroculus and Aricia + (Alpherakya + Glabroculus), which had low statistical support in molecular phylogenetic analysis. Additionally, in some cases molecular studies helped to reveal trends in the evolution of morphological traits. For example, the unpaired uncus and the compact juxta are not plesiomorphic for Cupidina as previously thought; instead, they were shown to have evolved secondarily within this subtribe.