Genetic Variability and Structuring of Arctic Charr (Salvelinus alpinus) Populations in Northern Fennoscandia

Abstract

Variation in presumably neutral genetic markers can inform us about evolvability, historical effective population sizes and phylogeographic history of contemporary populations. We studied genetic variability in 15 microsatellite loci in six native landlocked Arctic charr (Salvelinus alpinus) populations in northern Fennoscandia, where this species is considered near threatened. We discovered that all populations were genetically highly (mean F ST ≈ 0.26) differentiated and isolated from each other. Evidence was found for historical, but not for recent population size bottlenecks. Estimates of contemporary effective population size (N e) ranged from seven to 228 and were significantly correlated with those of historical N e but not with lake size. A census size (N C) was estimated to be approximately 300 individuals in a pond (0.14 ha), which exhibited the smallest N e (i.e. N e/N C = 0.02). Genetic variability in this pond and a connected lake is severely reduced, and both genetic and empirical estimates of migration rates indicate a lack of gene flow between them. Hence, albeit currently thriving, some northern Fennoscandian populations appear to be vulnerable to further loss of genetic variability and are likely to have limited capacity to adapt if selection pressures change.

Characterizing neutral and adaptive genomic differentiation in a changing climate: The most northerly freshwater fish as a model

“…High genetic differentiation based on neutral markers has also been previously reported for six landlocked populations of Arctic charr across Fennoscandia (Shikano et al, 2015), and 12 landlocked populations in Maine (Bernatchez et al, 2002). Like Linne´vatn and Ellasjøen (Bøyum & Kjensmo, 1978;Klemetsen et al, 1985), these lakes are of postglacial origin (<12,000 years old) but it is uncertain if any have been geographically isolated for a similar length of evolutionary time as Ellasjøen (Bernatchez et al, 2002;Shikano et al, 2015). Our findings suggest that the allopatric morphs in Linne´vatn and Ellasjøen are locally adapted, and thus, responses to climate change will be variable between the lakes.…”

“…The degree of genetic differentiation among Arctic charr morphs is an ongoing topic of research, and their distinction has mostly been investigated using neutral microsatellites and mitochondrial genes. Past studies that did not consider sympatric morphs often found that individuals from different lakes were distinguishable from one another (Brunner, Douglas, & Bernatchez, ; Primmer et al, ; Wilson et al, ), particularly where lakes are landlocked and geographically isolated (Bernatchez, Rhydderch, & Kircheis, ; Shikano, Järvinen, Marjamäki, Kahilainen, & Merilä, ). However, low genetic differentiation reported among anadromous individuals from some locations hundreds of kilometers apart likely reflects recent postglaciation colonization events over long distances (Alekseyev et al, ; Moore et al, ; Wilson et al, ).…”

“And if you gaze long into an abyss, the abyss gazes also into thee”: four morphs of Arctic charr adapting to a depth-gradient in Lake Tinnsjøen

“…Several studies have compared Arctic charr among lakes with regard to their genetic differentiation (where there may be lakes holding more than one morph of Arctic charr) revealing a F ST range of 0.003-0.627 when contrasted in Holarctic lakes [119–127]. Presence of two morphs associated (or not) with genetic clusters have been found in a number of Arctic charr lakes revealing a F ST range of 0.001-0.381 in Holarctic lakes [55, 60, 62, 66, 123–125, 128–133].…”

Landscape genetic structure of Scirpus mariqueter reveals a putatively adaptive differentiation under strong gene flow in estuaries

“…IBD effect was significant at large spatial scale, such as interregional scale (near 800 km between the two estuaries and Taiwan coastal areas) but nonsignificant at regional scale (approximate 20–300 km) when TW was excluded based on entire dataset. This result indicated that the S. mariqueter populations at the CRE or the QRE were deviate from the migration–drift equilibrium, which may be disrupted by the divergent selection process (Bradburd, Ralph, & Coop, ; Sexton et al, ; Shikano, Jarvinen, Marjamaki, Kahilainen, & Merila, ), the long‐distance dispersal or stochastic colonization. However, for these thirteen populations, compared with nonsignificant relationship between genetic differentiation and geographic distance with entire or neutral dataset, a significant strong IBD effect was detected with 21 outlier dataset, reflecting the effect of spatial distance on isolation seems to be promoted by divergent selection.…”