Low levels of hybridization between sympatricArctic char (Salvelinus alpinus) andDollyVarden char (Salvelinus malma) highlights their genetic distinctiveness and ecological segregation

Abstract

Understanding the extent of interspecific hybridization and how ecological segregation may influence hybridization requires comprehensively sampling different habitats over a range of life history stages. Arctic char (Salvelinus alpinus) and Dolly Varden (S. malma) are recently diverged salmonid fishes that come into contact in several areas of the North Pacific where they occasionally hybridize. To better quantify the degree of hybridization and ecological segregation between these taxa, we sampled over 700 fish from multiple lake (littoral and profundal) and stream sites in two large, interconnected southwestern Alaskan lakes. Individuals were genotyped at 12 microsatellite markers, and genetic admixture (Q) values generated through Bayesian-based clustering revealed hybridization levels generally lower than reported in a previous study (<0.6% to 5% of samples classified as late-generation hybrids). Dolly Varden and Arctic char tended to make different use of stream habitats with the latter apparently abandoning streams for lake habitats after 2–3 years of age. Our results support the distinct biological species status of Dolly Varden and Arctic char and suggest that ecological segregation may be an important factor limiting opportunities for hybridization and/or the ecological performance of hybrid char.

Occurrence of sympatric charr groups, Salvelinus, Salmonidae, in the lakes of Kamchatka: a legacy of the last glaciations

“…The level of hybridization between the species in Alaskan lake systems is minimal, c . 0·6% averaged over 12 microsatellite sites (May‐McNally et al, ). The analysis of three populations of S. taranetzi located in the Okhotsk Basin found the haplotype of S. malma to be the most common (Radchenko, , ).…”

“…These spawning traits promote the ongoing coexistence of these species in postglacial lakes and prevent the assimilation of low‐density landlocked S. taranetzi by more abundant S. malma . The same segregation in spawning and rearing habitats has been shown for Alaskan populations of S. taranetzi and S. malma (DeLacy & Morton, ; McPhail, ; May‐McNally et al, ; Taylor, ). Morphological, ecological and behavioural divergence for S. taranetzi and S. malma are already evident at the juvenile stage (Dennert et al, ).…”

Reliance on lakes by salmon, trout and charr (Oncorhynchus,SalmoandSalvelinus): An evaluation of spawning habitats, rearing strategies and trophic polymorphisms

“…When adfluvial, Dolly Varden usually migrate to lakes after a year or more of stream‐rearing (Esin, Myuge, Koval’, & Sorokin, ; Markevich, Esin, Busarova, Knudsen, & Anisimova, ) and seldom enter as fry (Bond, Miller, & Quinn, ; Roos, ). Dolly Varden display a rare version of this strategy in which some fry emerging from redds in a lake immediately migrate into a tributary stream where they rear for a year or more prior to re‐entering the lake; the others emerge in the lake and remain lacustrine (Esin et al., ; only S. fontinalis and S. alpinus are also known to exhibit this behaviour—Curry, Brady, Noakes, & Danzmann, ; May‐McNally, Quinn, & Taylor, ). Many anadromous Dolly Varden originating from a basin with a lake home, spawn in the natal river, and overwinter in that lake, whereas many of those originating from basins without lakes home to their natal river to spawn but then leave and find a lake in a non‐natal basin to overwinter (Armstrong, , , ; Bernard, Hepler, Jones, Whalen, & McBride, ).…”

Cytogenetic identification of genomic elements of brook trout ( Salvelinus fontinalis ) in the karyotype of Arctic char ( Salvelinus alpinus ) from the aquaculture broodstock

“…The global production of Arctic char reaches 6,000–10,000 metric tons/year and more than 90% contribution of fish produced under aquaculture conditions in Europe originates from the Nordic countries (Saether, Siikavuopio, Thorarensen, & Brännäs, ). It is well proven that Arctic char represents the highest phenotypic plasticity, ecological and genetic structure diversity among distinguished char species (Klemetsen, ; Kottelat & Freyhof, ; May‐McNally, Quinn, & Taylor, ; Reist, Power, & Dempson, ).…”

“…Mating of hybrids and purebreds may in turn results in production of the backcross individuals (Gross, Gum, Reiter, & Kuhn, ). Under natural conditions, F 1 and post‐F 1 hybrids of the Arctic char and Dolly Varden ( Salvelinus malma Walbaum, 1792) and the lake trout ( Salvelinus namaycush Walbaum, 1792) were evidenced (May‐McNally et al, ; Wilson & Hebert, ). Moreover, reciprocal and F 2 hybrids and backcrosses of Arctic char and brook trout ( Salvelinus fontinalis Mitchill 1814) are fertile (Faulks & Östman, ; Hammar, Dempson, & Verspoor, ; Ocalewicz, Hliwa, Pomianowski, Lisboa, & Jankun, ) and the introgressive hybridization leading to incorporation of Arctic char mitochondrial genome into genome of brook trout has been reported (Bernatchez, Glemet, Wilson, & Danzmann, ).…”