Genetic relationships between sympatric and allopatric Coregonus ciscoes in North and Central Europe

Abstract

Background Sympatric speciation along ecological gradients has been studied repeatedly, in particular in freshwater fishes. Rapid post-glacial ecological divergence has resulted in numerous endemic species or ecologically distinct populations in lakes of the temperate zones. Here, we focus on the Baltic cisco (Coregonus albula) complex, to study the genetic similarity among two pairs of sympatric autumn- and spring-spawning populations from post-glacial German Lakes Stechlin and Breiter Luzin. For comparison, we included a similar pair of sympatric populations from the Swedish Lake Fegen. We wanted to explore potential genetic similarities between the three sympatric cisco population pairs in the three lakes, to evaluate whether the pairs may have emerged independently in the three lakes, or whether two different species may have colonized all three lakes independently. Furthermore, we considered allopatric C. albula populations from three Polish, three Finnish, and four Swedish locations, added one Siberian population of the sister species C. sardinella and a Swedish C. maraena (whitefish) population. By genotyping nine microsatellite markers in 655 individuals from these 18 populations, we wanted to elucidate how strongly the cisco populations differ across a larger geographical area within Europe. Finally, we compared the genetic differences between the spring- and autumn-spawning populations of ciscoes in the two German lakes to infer the potentially deteriorating effect of strong anthropogenic pressure on the lakes. Results Dendrogram, Principal Coordinate Analysis and admixture analysis all indicated strong correspondence between population differentiation and geographical location for most cisco populations in Europe, including the Siberian population of C. sardinella. However, populations from some Swedish lakes deviated from this general pattern, by showing a distinct genetic structure. We found evidence for independent evolution of the three sympatric population pairs, because the populations co-occurring in the same lake were always most closely related. However, genetic differentiation was weak in the two German population pairs, but strong in the Swedish Lake Fegen, indicating that the weak differentiation in the German pairs reported earlier has eroded further. Conclusions Our results suggest that the genetic differentiation at neutral genetic markers among populations of the Baltic cisco complex has evolved (and is maintained) by random genetic drift in isolated populations. However, earlier studies on the Swedish populations combining mitochondrial DNA and microsatellite data indicate that also post-glacial immigration from separate glacial refugia has shaped the present genetic population structure. The low neutral differentiation of the German sympatric pairs in contrast to the Swedish pair suggests that recent anthropogenic effects on the lakes in Germany may put the endemic spring-spawners at risk to extinction.

Population genetics of the African snakehead fishParachanna obscuraalong West Africa's water networks: Implications for sustainable management and conservation

“…Angienda et al ( 2011 ) reported a relatively high genetic diversity for Oreochromis esculentus ( H O = 0.795–0.81, H S = 0.745–0.77, Ᾱ R = 7.13–8.13) and Oreochromis niloticus ( H O = 0.70–0.78, H S = 0.71–0.79, Ᾱ R = 7–8.38) populations in eastern Africa. Mehner et al ( 2021 ) found high genetic diversity in the European Coregonus cisco populations ( A R = 3.4–6.3). Many studies on the genetic diversity of other species from the Channidae family such as Channa striata (Adamson et al, 2012 ; Robert et al, 2019 ; Tan et al, 2016 ) and Channa marulia (Pathak et al, 2018 ) showed relatively high genetic diversity.…”

The ecology and fishery of the vendace (Coregonus albula) in the Baltic Sea

“…However, significant genetic differences between fish from between them. Interestingly, another species in the C. albula species complex (Mehner et al, 2021;Sendek et al, 2013;Sendek, 2021; Table 1), the closely related least cisco (Coregonus sardinella Valenciennes 1848), which inhabits many North American and Siberian freshwaters, can successfully occupy estuary waters of varying salinities up to 32 PSU (Craig, 1984). The populations assigned to each of these two Coregonus species are not monophyletic and are so much alike that some researchers argue that they constitute just one species (Borovikova et al, 2013;Borovikova & Artamonova, 2021), further suggesting a high potential for significant population-specific local adaptations within the C. albula species complex (potentially including the Baltic Sea populations).…”

Identifying and conserving sympatric diversity in trout of the genus Salmo, with particular reference to Lough Melvin, Ireland

“…Divergence may involve only a few genes under selection, possibly clustered throughout the genome (genomic islands), with the rest of the genome remaining largely homogenous as a result of gene flow (Franchini et al, 2013;Jacobs et al, 2018;Nosil et al, 2021). Smith and Skúlason (1996) and Skúlason et al (1999) While in practice, it can be difficult to differentiate between allopatric and sympatric origins, allopatrically evolved lineages might be expected to have colonised multiple waters and populations sharing genetic ancestry could be found elsewhere (Mehner et al, 2021). On the other hand, populations that have evolved in sympatry should share greater genetic ancestry to each other than to similar populations that have evolved in parallel in other waters.…”

“…While in practice, it can be difficult to differentiate between allopatric and sympatric origins, allopatrically evolved lineages might be expected to have colonised multiple waters and populations sharing genetic ancestry could be found elsewhere (Mehner et al, 2021). On the other hand, populations that have evolved in sympatry should share greater genetic ancestry to each other than to similar populations that have evolved in parallel in other waters.…”