Low levels of hybridization between sympatric Arctic char (Salvelinus alpinus) and Dolly Varden char (Salvelinus malma) highlights their genetic distinctiveness and ecological segregation.

Shannan L. May‐McNally,Thomas P. Quinn,Eric B. Taylor

doi:10.1002/ece3.1583

Shannan L. May‐McNally, Thomas P. Quinn + Show 1 more

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https://doi.org/10.1002/ece3.1583

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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.

Highlights

Natural hybridization is a fundamental evolutionary process in the biology of plants and animals (Mayr 1963; Arnold 1992; DeMarais et al 1992; Barton 2001)
We report the results of extensive sampling of Arctic char and Dolly Varden in Lake Aleknagik and Lake Nerka, southwestern Alaska to assess the following: (1) the degree of genetic divergence and levels of hybridization between species, and (2) the degree of interspecific ecological segregation and ontogenetic habitat use patterns by parental species and their hybrids
When examining samples pooled across sites within each lake and for Arctic char and Dolly Varden separately, 17 of 46 tests for deviations from Hardy–Weinberg equilibrium (HWE; two lakes x 12 loci for Arctic char plus two lakes x 11 loci for Dolly Varden) were significant at P ≤ 0.011

Summary

Introduction

Natural hybridization is a fundamental evolutionary process in the biology of plants and animals (Mayr 1963; Arnold 1992; DeMarais et al 1992; Barton 2001). When different species or genetically distinct populations interbreed, a wide variety of phenomena can result, for example, the formation of hybrid zones of various kinds, adaptive radiation, and reinforcement of pre- and postmating reproductive barriers during speciation (Schluter 1996; Arnold 1997; Dowling and Secor 1997; Seehausen 2004; Aboim et al 2010). Studying the level of hybridization, the structure of hybrid zones, and the viability of hybrids can assess the strength of isolation between evolutionarily young lineages and may signal factors relating to the origin and maintenance of species a 2015 The Authors.

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