Marin I.N. 2020. The Quaternary speciation in the Caucasus: a new cryptic species of stygobiotic amphipod of the genus Niphargus (Crustacea: Amphipoda: Niphargidae) from the Kumistavi (Prometheus) Cave, Western Georgia // Arthropoda Selecta. Vol.29. No.4: 419–432 [in English].
ABSTRACT. A new cryptic species of stygobiotic amphipod of the genus Niphargus Schiødte, 1849 (Amphipoda: Niphargidae) is described from underground stream and lakes in the Kumistavi (Prometheus) Cave, Tskaltubo–Kumistavi, Imereti region of the Western Georgia, Caucasus, based on morphology and DNA analysis. The new species belongs to the “carpathicus“ species complex with the representatives in Europe, Caucasus and Iran, but clearly differs from all Caucasian congeners by stout telson, which is about as long as wide (vs. about not less than 1.5 times in other related species); relatively stout basal part of dactyli of pereopods V–VII, which is about as long as wide (vs. usually more than 1.5 times as long as wide in other related species); and almost rectangular palm of gnathopods I and II with straight distal margin (vs. usually sloped distal margin in other related species). The sister species N. borutzkyi Birštein, 1933, inhabiting the neighboring, but isolated underground karst system, including of the Sataplia, Sapichkhia and Tskaltsitela caves, differs from the new species in some minor morphological features and genetically (about 10% or 0.1 substitutions per 100 nucleotides by COI gene marker). The phylogenetic analysis of available genetic data (COI mtDNA) shows that karsts regions in the vicinity of Kutaisi are currently inhabited by closely related Niphargus species descended from the ancestral taxon in the Quaternary as a result of geological processes that caused fragmentation of the ancestral range.
KEY WORDS: Crustacea, Amphipoda, Niphargidae, Niphargus, new species, stygobiotic, Western Georgia, Caucasus.