Investigation on the origin of the "nose" in the genus Megalothorax Willem, 1900 (Neelidae, Collembola) by the means of integrative taxonomy.

Megalothorax Willem, 1900 is a genus of Collembola that comprises 36 species to date. For a long time, its diversity was overlooked, but recent integrative taxonomic works allowed us to understand better their seemingly cryptic diversity. Among the oddities of the genus are the so-called "nosed" species, i.e. species equipped with a frontal cuticular process, an unusual trait for Collembola. In this work, we describe a new "nosed" species from the north of European part of Russia and redescribe the first known "nosed" species: Megalothorax sanctistephani Christian, 1998. This species is known only from peculiar places: initially the catacombs of a cathedral in Vienna, and our new findings in underground tunnel in Paris and Botanical Garden of Kaliningrad. We also used long-read sequencing to obtain new DNA data for "nosed" species of Collembola. We investigated the evolution of the "nose" using molecular and morphological phylogeny approaches. This evolution remained unclear, as molecular and morphological data are conflicting on this specific point. The "nose" may have been acquired a single time, then lost secondarily in some species; or have been acquired independently several times.