European colonization by the spined loach (Cobitis taenia) from Ponto‐Caspian refugia based on mitochondrial DNA variation

Abstract

In the last 20 years, new species, asexual reproduction, polyploidy and hybridization have all been reported within the genus Cobitis. An understanding of the current distribution and baseline phylogeographical history of 'true' nonhybrid Cobitis species is crucial in order to unravel these discoveries. In the present work, we investigated the phylogeography of the spined loach, Cobitis taenia, using 1126 bp of the mitochondrial cytochrome b gene from 174 individuals collected at 47 sites. In total, 51 haplotypes that differed at 49 positions (4.35%) were detected. We deduce that C. taenia survived European glaciations in at least three refugees in the Ponto-Caspian area. Two of these refugees each provided a major lineage that recolonized Europe in separate directions: one westward to England and the other spreading north into Russia before moving west. A third (minor) lineage that contributed little to the recolonization of Europe was also revealed--remaining near its Black Sea refuge. However, more recent history was difficult to resolve with colonization from a more western refugium during the last glacial maximum (LGM) a distinct possibility. Nested clade analysis indicates a pattern of restricted gene flow with isolation by distance at the first two levels and overall. Unlike many other European freshwater fish species, the Danube is not part of the current distribution of C. taenia, nor was it used as either a refuge or a source of colonization of Europe. Low genetic diversity within C. taenia suggests that its colonization of Europe is relatively recent. Demographic analyses revealed a history of recent expansion and isolation by distance.

The Identification of a Novel, High Frequency Variant in the Cytochrome b Gene in an Isolated Population of a Rare Fish, Spined Loach <i>Cobitis taenia</i>, in England: A Population Worth Protecting?

“…The variant has not been reported before in any of the haplotypes previously assigned to English [3] or European populations of C. taenia or to Cobitis spp. ; indeed, the authors are only aware of a change in the amino acid at this location (isoleucine instead of valine) in Cobitis choii (Blast Pbuild 2.2.30) suggesting that, at least in Cobitis spp.…”

“…This would suggest that perhaps the polymorphism is due to genetic drift rather than natural selection as no fitness benefit is apparently evident [14], however, the relatively high frequency of this variant may suggest that there is a founder effect in action. Indeed, in the River Mease, a tributary further downstream on the River Trent, all fish were described as Haplotype "1" [3]. Figure 1 shows the distance in river kilometres between the three sites in the current study and the two sites downstream, denoted C1 (River Mease) and C2 (River Trent at Stoke Bardolph), studied by Culling et al [3].…”

“…Total DNA was extracted using the Nucleon Genomic DNA extraction kit HT (Tepnel Life Sciences, Manchester, UK) according to the manufacturer's instructions, dissolved in Tris-EDTA buffer (pH 8.0) overnight at 4˚C and stored at −20˚C prior to further processing. For amplification of the entire cytochrome b gene the primers used were adapted from [3]: the forward primer (GluDG. L) was 5'-TGACTTGAARAAC- at The Sequencing Service, University of Dundee (Dundee, UK).…”

“…Limited swimming ability, along with the patchy distribution of suitable habitat, restricts the distribution of the species and potentially isolates populations. Phylogeographic studies can How to cite this paper: Rahbari, R., Tannahill, K., Tobin, C., Robotham help to establish historical genetic lineage and geographical distribution of a species [2] [3]. This information is vital to gain an understanding of taxonomic diversity and, in conjunction with ecological considerations, form conservation management strategies for rare or threatened species [4].…”

“…Studies conducted by Culling and Côte [6] and Culling et al [3] aimed to infer phylogeographical patterns of Cobitis taenia through analysis of the mtDNA gene cytochrome b. Fifty one different haplotypes were identified as currently being present throughout the European populations and phylogenetic analysis indicated that after the last glacial maximum, three refuges in the Ponto-Caspian area of the Black Sea basin gave rise to two major lineages that re-colonised Europe. One of these lineages moved west, utilising the still present land bridge to colonise England in the upper part of the late Pleistocene.…”