Barbatula spp

Alexander, Timothy & Seehausen, Ole, 2021, Diversity, distribution and community composition of fish in perialpine lakes – “ Projet Lac ” synthesis report, Eawag: Swiss Federal Institute of Aquatic Science and Technology : 130-131

Barbatula spp (stone loach)

Six species of Barbatula (stone loach) are currently known from Europe:Barbartula quignardi from northern Spain and southern France; B. leoparda from a tiny Mediterranean drainage in French Catalonia; B. sturanyi , B. zetensis and B. vardarensis all have small distribution ranges on the Balkan region; and B. barbatula from the rest of Europe. Large morphological variation within B. barbatula has long been suspected to indicate the presence of several additional, undescribed species [9]. Indeed, a phylogeographic study by Sediva et al [151] revealed that B. barbatula consisted of many, deeply divergent mitochondrial lineages, with some originating in the Pleistocene (2.6 million – 12 thousand years ago) and even the Miocene (23 – 5 million years ago). The three described Balkanian species are phylogenetically all nested within this large group of lineages commonly referred to collectively as B. barbatula . Prior to Projet Lac, it was not known which of these lineages occurred in Switzerland and around the perialpine region.

Barbatula were recorded in Projet Lac in lakes Chalain, Geneva, Constance, Walen, Zurich, Zug, Lucerne, Biel and Neuchatel. Large variation in colour pattern and head shape were evident among the collected fish, both within and among lakes. Sequencing the COI mitochondrial gene (barcode) and comparison with sequences on GenBank (an online database of genetic sequences) revealed the presence of Barbatula quignardi in the Rhone catchment in lakes Chalain and Geneva, as well as in the fish collected by Progetto Fiumi from the Allaine River. Morphologically, populations of B. quignardi tended to differ from the others by having a deeper caudal peduncle.

The remaining barcoded Barbatula consisted of two distinct lineages. One lineage was recorded by Projet Lac in the lakes of the Aare-Rhine (including Limat and Reuss river subcatchments; Neuchatel, Biel, Walen, Zurich, Lucerne, Zug), while in Progetto Fiumi, the only river that this lineage was recorded from was the Sense River. Populations of this lineage are referred to in this report as Barbatula sp. Lineage I. Fish of this lineage seem to be mostly composed of smaller fish with blunt snouts and high-contrast, large, dark blotches (although those in Lucerne were somewhat paler and larger).

The second lineage was widespread among the streams and rivers of the Aare-Rhine (including the River Sense; based on Progetto Fiumi), but was recorded in Projet Lac in only one lake of this catchment (Lake Zürich Obersee). On the other hand this was the loach recorded in lakes Geneva and Constance outside the Aare-Rhine catchment.This lineage is referred to in this report as Barbatula sp Lineage II.These fish appeared to grow larger than most fish we collected of the populations of Barbatula sp. Lineage I. The fish of Lake Constance were particularly variable, with enormous differences in colour pattern and head shape. Barluenga et al [142] had previously described the unusually large genetic variation and very high genetic differentiation between some populations of Barbatula in Lake Constance. It is not impossible that there are two different species in Lake Constance and this situation requires attention in the future.

Barbatula sp. “Lineage II” and B. quignardi turned out to be sister taxa in the barcode tree, whereas B. sp. “Lineage I” was the sister lineage of both of these together and all three belonged to the Western clade of Sediva et al. The most surprising finding here is that B. sp. “Lineage I” and B. sp. “Lineage II” are geographically fully sympatric in the Aare-Rhine, but seem to partition the macrohabitat between them with Lineage I mostly confined to the streams (only exception Lake Zürich Obersee) and Lineage II mostly confined to the lakes (only exception the Sense River).This situation requires further investigation in the future.