Morphology of the mandibles and the first maxillae in the family Lithobiidae (Myriapoda, Chilopoda), with remarks on their phylogenetic significance

Abstract

The mandibles and the first maxillae of 37 species of the family Lithobiidae (Myriapoda, Chilopoda) were investigated and compared to provide a structural overview and evaluate their significance for the systematics of the family. The species sampling focused on the genus Lithobius, examining 33 species of four subgenera (Lithobius, Monotarsobius, Sigibius, Ezembius), as this genus represents about half of the known diversity of Lithobiidae, including more than 500 assigned species and subspecies. The microstructures on the mandibular gnathal edge and the first maxillary telopodites and coxal projections were studied using scanning electron microscopy. Although having a similar structural pattern, we demonstrate that the microstructures are variable within and between species of adult specimens and commonly show intergradation. To check for intraspecific variability of microstructures and character stability, specimen sampling was extended for the two common Austrian species Lithobius dentatus and Lithobius validus, for which seven specimens depicted no major differences in the mandibular gnathal edge and the first maxillae. Our data suggest the presence of three characters in the mandibular gnathal edge and the first maxillae useful for lithobiid phylogeny. These characters were tested in a phylogenetic analysis together with previously described and novel morphological characters. Subgenera of Lithobius are mostly non‐monophyletic, and several other genera of Lithobiinae as well as other subfamilies group with particular species or clades of Lithobius. The results corroborate a close relationship between Disphaerobius loricatus and Lithobius (Ezembius) giganteus, strengthening the hypothesis that Pterygoterginae is nested within Lithobiinae and specifically within Lithobius, allied to L. (Ezembius) and Hessebius.

Phylogeny of Lithobiidae Newport, 1844, with emphasis on the megadiverse genus Lithobius Leach, 1814 (Myriapoda, Chilopoda)

“…In a morphological cladistic analysis, representative species of the lithobiid genera Australobius Chamberlin, 1920, Hessebius Verhoeff, 1941, Harpolithobius Verhoeff, 1904 and Pleurolithobius Verhoeff, 1899, were each allied to particular species within Lithobius (Koch and Edgecombe, 2008). A subsequent phylogenetic analysis with new detailed information from the peristomatic structures, namely the epipharynx and hypopharynx, mandibles and first maxillae from a sample including 33 representatives from four of the eight subgenera ( Lithobius , Monotarsobius , Sigibius , Ezembius ), further supported the polyphyly of the genus Lithobius (Ganske et al, 2018a,b). However, a phylogenetic study including six species of Lithobius together with three species of Ethopolyinae and one species of Australobius provided weak molecular support for monophyly of Lithobius (Murienne et al, 2010).…”

“…The outgroup is the scutigeromorph Scutigera coleoptrata . Voucher specimens are deposited at the Natural History Museum Vienna (NHMW), the Hungarian Natural History Museum Budapest (HNHM), the Zoological Museum of the University of Turku (ZMUT) and the Senckenberg Museum of Natural History Görlitz (SMNG) (Supplements 1, 2 and Ganske et al, 2018a,b).…”

“…However, a phylogenetic study including six species of Lithobius together with three species of Ethopolyinae and one species of Australobius provided weak molecular support for monophyly of Lithobius (Murienne et al, 2010). The analyses conducted by Ganske et al (2018a) also resolved the sampled subgenera of Lithobius as nonmonophyletic, except for the subgenus Sigibius under parsimony. However, morphology alone was not sufficient to resolve certain species inter‐relationships except for a few species groups (see Ganske et al, 2018a).…”

“…The analyses conducted by Ganske et al (2018a) also resolved the sampled subgenera of Lithobius as nonmonophyletic, except for the subgenus Sigibius under parsimony. However, morphology alone was not sufficient to resolve certain species inter‐relationships except for a few species groups (see Ganske et al, 2018a). The study also included additional representatives from other lithobiid subfamilies and genera, and the data further support Ethopolyinae and Pterygoterginae to cluster within Lithobiinae (Ganske et al, 2018a).…”

“…Edgecombe and Giribet, 2004), and Scutigera coleoptrata (Linnaeus, 1758) (Scutigeromorpha) as outgroup. An existing morphological dataset based on 62 characters (Ganske et al, 2018a) was additionally included in the analyses and supplemented with new morphological data from additional species.…”