Lithobius: a big genus of a small subphylum (Arthropoda, Myriapoda) - phylogeny and evolutionary history

Phylogenetic analyses based on molecular and morphological data were conducted to shed light on relationships within the mostly Palaearctic/Oriental centipede family Lithobiidae, with a particular focus on the Palaearctic genus Lithobius Leach, 1814 (Lithobiidae, Lithobiomorpha), which contains >500 species and subspecies. Previous studies based on morphological data resolved Lithobius as nonmonophyletic, but molecular‐based phylogenetic analyses have until now sampled few species. To elucidate species inter‐relationships of the genus, test the validity of its classification into subgenera, and infer its relationships with other Lithobiidae, we obtained molecular data (nuclear markers: 18S rRNA, 28S rRNA; mitochondrial markers: 16S rRNA, COI) and 61 morphological characters for 44 species of Lithobius representing four of its eight subgenera and nine other representatives of Lithobiidae. The data were analyzed phylogenetically using maximum‐likelihood, parsimony and Bayesian inference. This study suggests that (i) a close relationship between L. giganteus and the pterygotergine Disphaerobius loricatus highlighted in recent morphological analyses is also strongly supported by molecular data, and Pterygoterginae is formally synonymized with Lithobiinae; (ii) the Oriental/Australian genus Australobius is consistently resolved as sister group to all other sampled Lithobiidae by the molecular and combined data; (iii) the subfamily Ethopolyinae may be paraphyletic; (iv) the genus Lithobius is nonmonophyletic; (v) the subgenera Lithobius, Sigibius and Monotarsobius are nonmonophyletic and should not be used in future taxonomic studies; and (vi) there are instances of cryptic species and cases in which subspecies should be elevated to full species status, as identified for some European taxa within Lithobius.

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 L. dentatus and L. 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 nonmonophyletic, 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.

Morphological characters have been widely used in centipede systematics. Here, we aim to obtain morphological information from the preoral chamber and peristomatic structures of lithobiomorph centipedes, with taxonomic sampling focused on the species-rich genus Lithobius Leach, 1814. Towards this goal, we (i) examined the epipharynx and hypopharynx of 32 species belonging to four subgenera of the genus Lithobius , viz. Lithobius Leach, 1814, Monotarsobius Verhoeff, 1905, Sigibius Chamberlin, 1913 and Ezembius Chamberlin, 1919 using light and scanning electron microscopy, (ii) searched for phylogenetically informative characters and (iii) described interspecific variation. Three species of the lithobiid genera Eupolybothrus Verhoeff, 1907, Disphaerobius Attems, 1926 and Neolithobius Stuxberg, 1875 were additionally examined and considered as likely outgroups. New characters and character states are proposed as additions to current phylogenetic datasets. Similarities in the peristomatic structures ally Disphaerobius with Lithobius (Ezembius), suggesting that the subfamily Pterygoterginae is nested within Lithobiinae and Lithobius .

Since the species interrelationships of the centipede genus Lithobius Leach, 1814 are not clear, we examined the microstructures on the mandibular gnathal edge as a source for phylogenetic useful information.