Cryptic expansion of hybrid polyploid spined loaches Cobitis in the rivers of Eastern Europe

Endangered spined loach Cobitis species in Southwest Germany: A complex network of native, hybrid and newly emerged populations

“…Surprisingly, maternal haplotypes of C. taenia and C. elongatoides often co‐occurred in the Upper Rhine River. Our microsatellite data of a mixed population identified C. elongatoides as a dominating hybrid biotype and C. taenia as a diploid parental species – a pattern which has been reported in large rivers (Lusk et al, 2003; Mezhzherin et al, 2022) and a previous downstream survey in the Rhine (Janko, Flajšhans, et al, 2007). As eDNA analysis consistently yielded higher detection rates of C. elongatoides on sites with both haplotypes present, we conclude that the Upper Rhine in contrast to the previous assessment is today largely inhabited by hybrid complexes of C. elongatoides and C. taenia .…”

“…This species has been previously reported in Swiss lakes and tributaries to the Rhine, such as the Aare system (Alexander & Seehausen, 2021; Zaugg & Capt, 2022), so it may have spread naturally (Figure 7). A similar range expansion has also been observed in hybrid polyploid Cobitis populations in Eastern Europe in recent decades, presumably due to changing environmental conditions and increased viability of polyploids (Mezhzherin et al, 2022).…”

“…Our study is the first to uncover a complex network of native, hybrid (b) (a) Mezhzherin et al, 2022) and a previous downstream survey in the Rhine . As eDNA analysis consistently yielded higher detection rates of C. elongatoides on sites with both haplotypes present, we conclude that the Upper Rhine in contrast to the previous assessment is today largely inhabited by hybrid complexes of C. elongatoides and C. taenia.…”

“…Most are morphologically similar, and visual identification at the species level can be challenging (Buj et al, 2014; Kotusz, 2000). Their identification is further complicated by the number of hybrid populations that have been identified within the genus (Bohlen & Rab, 2001; Mezhzherin et al, 2022). These hybrid populations consist almost exclusively of predominantly polyploid females that can reproduce semi‐clonally by gynogenesis (Fedorčák et al, 2018; Janko, Bohlen, et al, 2007).…”

Triploid forms’ karyotypes of spined loaches from the genus Cobitis (Actinopterygii: Cypriniformes: Cobitidae) of the upper Dnieper and Western Dvina rivers: Analysis of the triploids’ origin

“…The first clonal-bisexual (diploid-polyploid) complex in the genus Cobitis was noted in 1981 in the Volga River basin (Vasil′ev and Vasil′eva 1982;Vasil′ev et al 1989). Further studies revealed the wide distribution of diploid-polyploid loach complexes in the Volga River basin, as well as in the rivers of the Black, Baltic, and North seas (Vasil′ev 1990;Boroń 1992Boroń , 1995Boroń , 1999Boroń , 2003Ráb and Slavik 1996;Vasil′eva and Vasil′ev 1998;Boroń and Danilkiewicz 1998;Bohlen and Ráb 2001;Bohlen et al 2002;Vasil′ev et al 2005Vasil′ev et al , 2007Vasil′ev et al , 2011Janko et al 2007Janko et al , 2012Choleva et al 2008;Buj et al 2008;Mezhzherin et al 2022). The structure of these complexes varies, but their obligatory elements are at least one all-female form and one diploid bisexual species (host), which is a sperm donor for gynogenetic reproduction.…”