Integrative taxonomy helps to revise systematics and questions the purported cosmopolitan nature of the type species within the genus Diaforobiotus (Eutardigrada: Richtersiusidae)

Abstract

Recent advances in tardigrade taxonomy have been greatly enhanced by the redescriptions of the type species for particular taxa or species groups. De novo characterisation of these key taxa now allows to describe tardigrade species diversity with improved precision and at higher rate, increasing the momentum towards resolving the taxonomic impediment in these micro-invertebrates. Since its description, Diaforobiotus islandicus (Richters, 1904) has been reported from many distinct localities around the world. This suggested, perhaps falsely, a cosmopolitan nature of the species. However, potential erroneous assignment of newly found populations to this species could be a result of the very general and superficial original description. In order to properly recognise and name species diversity within the genus, I provide here an integrative redescription of the type species (D. islandicus) with a neotype designation, a description of a new species, Diaforbiotus svalbardicus sp. nov, and dichotomous key for the genus. Both descriptions are based on detailed morphological and morphometric data associated with standard DNA sequences of four genetic markers (18S rRNA, 28S rRNA, ITS-2, and COI). The genus composition and diagnosis amendments of the family Richtersiuside are also discussed. The presented study constitutes a starting point for further systematic studies on the genus Diaforobiotus and new taxa discoveries.