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.
Highlights
This taxon closely approaches and likely comes into contact with H. h. hippophaes in Ukraine and H. h. baltistana in NE Afghanistan. The latter taxon is apparently restricted to NE Afghanistan, Pakistan and NW India, but any overlap or contact zone with H. h. bienerti is still to be ascertained
We found that clade 1, 2 and 3 are not geographically isolated but mostly resemble the species ranges of H. hippophaes and H. chamyla, with exceptions where individuals can be found in the other clades, as described above
The basal split between H. livornica/H. salangensis/H. nicaea/H. gallii and the five clades of H. hippophaes/H. chamyla/H. vespertilio (Figure 6, posterior probability (PP) = 1) is congruent with the results of previous molecular publications [1,3,25] in setting the first four species well apart both from each other and from the cluster formed of H. hippophaes/H. chamyla/H
Summary
The Western Palaearctic species of the globally distributed hawkmoth genus Hyles (Lepidoptera: Sphingidae) have long been the subject of extensive molecular phylogenetic research [1,2]. The genus has emerged as a model for the study of mito-nuclear mismatch [3], dynamic gene flow and the effects of the heterogeneous use of molecular and morphological markers in taxonomic decisions, which in turn have influenced decisions regarding how many biological species should be recognized in the Western Palearctic [2]. This area encompasses the greatest species richness, with approximately 17 species occurring in the region [4,5], and the greatest life history and morphological trait diversity [6,7]. Recent research has revealed that this diversity is relatively young, at 6.5 Ma [7], and that the speciation processes are still ongoing, which has led to a complex pattern of taxa that are in the process of both merging or diverging
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