Aim: Freshwater subterranean amphipods (genus Niphargus) with low dispersal abilities are known from both sides of the impermeable barrier, the Adriatic Sea. We tested the hypothesis that historical marine regression–transgression cycles shaped the distribution patterns of subterranean amphipods through repeated cycles of dispersal and vicariance against the hypothesis that subterranean amphipods colonized both sides of the Adriatic Sea independently. Methods: The taxonomic structure of the studied clade was revised using unilocus species delimitation methods. The timeframe of cladogenetic events was inferred using a multi-locus time-calibrated phylogeny and compared to the main regression–transgression events in the Miocene and Pleistocene. The geographical origin of the studied clade, species range expansions and contractions, as well as vicariance events were assessed through modelling of historical biogeography. Results: Subterranean amphipods of the genus Niphargus, found on both sides of the Adriatic Sea, form a monophylum. The reconstructions of ancestral ranges suggest that the clade emerged in the Balkan Peninsula, dispersed three times independently to the Apennine Peninsula and once back to the Balkans. Adriatic Islands were colonized multiple times, predominantly from the Balkan Peninsula. The dispersal–vicariance events correspond to historical regression–transgression cycles in Miocene and Pleistocene. Main conclusions: Marine regression–transgression cycles apparently shaped the distribution patterns of subterranean amphipods while the alternative hypothesis received no support. The actual distribution of subterranean faunas apparently reflects old biogeographical events.
COBISS.SI-ID: 18554627
We tested the hypothesis that sympatry among closely related species is possible only in the absence of interspecific competition. The hypothesis was tested on a clade of subterranean amphipods, genus Niphargus, distributed in the Dinaric Karst, Western Balkan, Europe, by employing phylogenetic reconstructions; species delimitation; modelling competition using phylogeny and species distributions and reconstruction of historical dispersal. The results show that the clade comprises six species, which classify into two ecomorphs. Species of the same ecomorph are parapatric or allopatric, whereas species belonging to different ecomorphs overlap their ranges. The phylo-spatial reconstructions suggest that the shift from allopatry to sympatry is associated with relaxation of competitive interactions. The overall conclusion is that interspecific competition presumably controls evolutionary and ecological dynamics in subterranean environments in a similar way as in more familiar surface environments.
COBISS.SI-ID: 4969039
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.
COBISS.SI-ID: 51928067