The genus Microniphargus (Crustacea, Amphipoda): evidence for three lineages distributed across northwestern Europe and transfer from Niphargidae to Pseudoniphargidae

Microniphargus leruthi Schellenberg, 1934 (Amphipoda: Niphargidae) was first described based on samples collected in Belgium and placed in a monotypic genus within the family Niphargidae. However, some details of its morphology as well as recent phylogenetic studies suggest that Microniphargus may be more closely related to Pseudoniphargus (Amphipoda: Pseudoniphargidae) than to Niphargus. Moreover, M. leruthi ranges over 1,469 km from Ireland to Germany, which is striking since only a few niphargids have confirmed ranges in excess of 200 km. To find out the phylogenetic position of M. leruthi and check whether it may be a complex of cryptic species, we collected material from Ireland, England and Belgium then sequenced fragments of the mitochondrial cytochrome c oxidase subunit 1 gene as well as of the nuclear 28S ribosomal gene. Phylogenetic analyses of both markers confirm that Microniphargus is closer to Pseudoniphargus than to Niphargus, leading us to reallocate Microniphargus to Pseudoniphargidae. We also identify three congruent mito-nuclear lineages present respectively in Ireland, in both Belgium and England, and in England only (with the latter found in sympatry at one location), suggesting that M. leruthi is a complex of at least three species with a putative centre of origin in England.