First insight into cryptic diversity of a Caucasian subterranean amphipod of the genus Niphargus (Crustacea: Amphipoda: Niphargidae)

The Caucasus region harbors a rich subterranean amphipod fauna. However, it was rarely studied using molecular tools. Recent field explorations unveiled a number of populations that morphologically correspond to the little known amphipod Niphargus alasonius described from Georgia. The populations are distributed along the Kura River drainage, spanning a range that exceeds 300 km. This unusually broad distribution implies that N. alasonius is a good disperser, exploiting the riverine interstitial as a distributional corridor, or alternatively, that it is a complex of cryptic species. We tested these two hypotheses using a molecular genetic approach. Multilocus phylogenetic analysis suggested that N. alasonius is a monophyletic taxon, closely related to Crimean taxa. Species delimitations and molecular dating imply that N. alasonius comprises at least five closely related cryptic species that diverged during the Late Miocene/Early Pliocene. Since these putative species are distributed along the entire drainage system, we hypothesized that the Kura River played a crucial role in shaping biogeographic patterns of this species. To promote further research of subterranean amphipods in the region, we provide a checklist of Caucasian Niphargus, and define shared morphological traits of the N. alasonius species complex. (c) 2020 Elsevier GmbH. All rights reserved.

Automated summary

The study revealed a rich subterranean amphipod fauna in the Caucasus region, focusing on the molecular genetic approach to uncover the presence of at least five closely related cryptic species within the N. alasonius taxon. These cryptic species were found to have diverged during the Late Miocene/Early Pliocene and are distributed along the entire Kura River drainage system, suggesting the river played a crucial role in shaping their biogeographic patterns.