The Phylogenetics and Biogeography of the Central Asian Hawkmoths, Hyles hippophaes and H. chamyla: Can Mitogenomics and Machine Learning Bring Clarity?

Abstract

The western Palaearctic species of the hawkmoth genus Hyles (Lepidoptera: Sphingidae) have long been the subject of molecular phylogenetic research. However, much less attention has been paid to the taxa inhabiting the central and eastern Palaearctic, particularly Central Asia, where almost 50% of the species diversity of the genus occurs. Yet, many taxonomic conundrums hinder a proper assessment of the true diversity in these moths. One still unresolved group of species includes Hyles hippophaes and Hyles chamyla. Despite a largely overlapping morphology and ecology, a plethora of infraspecific taxa display some unique divergent characters over a wide geographical area. In this study, we undertook a taxonomic assessment of each population and resolved this species complex using an integrative approach. A combination of new computational techniques (DAISY-II) in comparative morphology and recent advances in DNA extraction methods and sequencing of museum specimens (WISC) alongside more traditional genetic approaches allowed testing of the three main phenotypes—bienerti, chamyla and apocyni—in terms of their morphological, mitochondrial and biogeographical integrity, and to elucidate their evolutionary relationships. Our results support the existence of two closely related species, Hyles chamyla and H. hippophaes, but the former species H. apocyni (here discussed as the ecological form apocyni of H. chamyla) is best regarded as a hybrid between H. chamyla and H. h. bienerti. The results indicate that the evolutionary relationship between H. chamyla and H. hippophaes is one of admixture in the context of ongoing ecological differentiation, which has led to shared morphological characters and a blurring of the species boundaries. These results clarify the evolutionary relationships of this species complex and open future research lines, including the analysis of nuclear markers and denser sampling, particularly of H. hippophaes and H. vespertilio in western Europe.