Split distribution, biogeography and morphological and genetic diversity of the Iberobathynellini Tribe in the family Parabathynellidae (Crustacea, Malacostraca, Bathynellacea)

The “Iberobathynella group”, or Iberobathynellini tribe, is a complex of six genera consisting of 33 nominal species and several cryptic species with an amphiatlantic distribution (in Europe, North Africa and North America). A modern systematic revision of this group of subterranean crustaceans is presented here. A phylogenetic and biogeographic study using morphological and molecular data (mitocondrial coi and nuclear 18S) was carried out and allowed to a) re-evaluate the taxonomic status and validity of previously erected subtribes, genera and subgenera that show congruence in the data; b) assess whether the identified mitochondrial lineages represent cryptic species; c) provide a plausible phylogenetic hypothesis for the relationships within Iberobathynellini and with the other two genera of the family Parabathynellidae that inhabit North America and Europe (Montanabathynella and Parabathynella, respectively); d) propose a plausible temporal and historical framework (paleobiogeographic scenario) for the diversification and evolution of the Iberobathynellini tribe based on the current distribution of morphotypes and their estimated times of divergence. Our results show that in parabathynellids, molecular and morphological divergences are not always congruent. Subtribe and subgenus are invalid categories so they must be eliminated. Paraiberobathynella genus needs to be revisited. The molecular dating results support the early divergence of the Iberobathynellini Tribe (Upper Cretaceous, around 78 Mya) and the vicariance by plate tectonics as main factor to explain the amphi-Atlantic distribution shown by this ancient subterranean crustacean group. Since there are species morphologically very similar to I. magna and I. imuniensis, but genetically different, we can ensure the existence of at least three cryptic species. Texanobathynella is undoubtedly a valid genus distinct from Iberobathynella. Montanabathynella and Parabathynella are two well-differentiated genera closely related to the Iberobathynellini tribe.