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.

高加索地区拥有丰富的地下两栖类动物。但是，很少使用分子工具进行研究。最近的野外勘查揭示了许多种群，这些种群在形态上与佐治亚州描述的鲜为人知的两栖动物Niphargus alasonius相符。人口分布在库拉河（Kura River）流域，覆盖范围超过300公里。这种异常广泛的分布表明，N。alasonius是很好的散布者，利用河川间质作为分布走廊，或者，它是一个复杂的隐性物种。我们使用分子遗传学方法检验了这两个假设。多基因座系统发育分析表明，阿拉森猪笼草是一种单分类单元，与克里米亚分类单元密切相关。物种划分和分子测年表明，阿拉森猪笼草包括至少五个紧密相关的隐性物种，这些物种在中新世晚期/上新世早期分化。由于这些推定物种分布在整个排水系统中，因此我们假设库拉河在塑造该物种的生物地理格局方面起着至关重要的作用。为了促进对该地区地下两栖动物的进一步研究，我们提供了高加索尼古拉斯（Niagargus）的清单，并定义了阿拉森猪笼草物种群的共同形态特征。