Zoogeography of epigean freshwater Amphipoda (Crustacea) in Romania: <br />fragmented distributions and wide altitudinal variability

Abstract

Inland epigean freshwater amphipods of Romania are diverse and abundant for this region has a favourable geographical position between the Balkans and the Black Sea. Excluding Ponto-Caspian species originating in brackish waters and freshwater subterranean taxa, there are 11 formally recognized epigean freshwater species recorded from this country. They belong to 3 genera, each representing a different family: Gammarus (Gammaridae, 8 species or species complexes), Niphargus (Niphargidae, 2 epigean species) and Synurella (Crangonyctidae, one species). Their large-scale distribution patterns nevertheless remain obscure due to insufficient data, consequently limiting biogeographical interpretations. We provide extensive new data with high resolution distribution maps, thus improving the knowledge of the ranges of these taxa. Gammarus species display substantial altitudinal variability and patchy, fragmented distribution patterns. They occur abundantly, particularly in springs and streams, from lowlands to sub-mountainous and mountainous regions. In the light of recent molecular research, we hypothesize that the complex geomorphological dynamics of the Carpathian region during the Late Tertiary probably contributed to their allopatric distribution pattern. Contrasting with Gammarus, the genera Niphargus and Synurella exhibit low altitudinal variability, broad ecological valences and overlapping distributions, being widespread throughout the lowlands. The current distribution of N. hrabei and N. valachicus seems to be linked to the extent of the Paratethys during the Early Pliocene or Pleistocene. We further discuss the taxonomic validity of two synonymized and one apparently undescribed taxon, and provide an updated pictorial identification key that includes all taxa and forms discussed in our study. The mosaic distribution of epigean freshwater amphipod species in Romania shows that this region is particularly suitable for phylo-and biogeographical analyses of this group.

The southwestern Carpathians as an ancient centre of diversity of freshwater gammarid amphipods: insights from the Gammarus fossarum species complex

“…In the Carpathians, it has a patchy distribution and is found only in the western and southwestern part of these mountains (Grabowski & Mamos ; Copilaş‐Ciocianu et al . ; see also Fig. ).…”

“…This distribution encompasses two isolated regions (Copilaş‐Ciocianu et al . ): the northern one in the western part of the Apuseni Mountains and the southern one in the western half of the Southern Carpathians (Fig. ).…”

“…; Živić & Marković ; Grabowski & Mamos ; Copilaş‐Ciocianu et al . ). Geographical distribution of the main clades is represented by geometrical shapes that correspond with the phylogeny.…”

“…), we hypothesized that this pattern might have been influenced by the complex geomorphological past of the region (Copilaş‐Ciocianu et al . ).…”

“…In a study summarizing present‐day distribution patterns, we have shown that in the southern half of the Carpathians, Gammarus species exhibit mosaic‐like distributions (Copilaş‐Ciocianu et al . ), which might reflect the influence of historical rather than contemporary factors (Lomolino et al . ).…”