Differentiation of Sympatric Arctic Char Morphotypes Using Major Histocompatibility Class II Genes

Abstract

Arctic Char Salvelinus alpinus have colonized northern postglacial lakes within the last few thousand years. Divergent populations have adapted to thrive in the prevailing oligotrophic environments and thus have developed morphotypes with different ecological behaviors. The morphotypes usually differ in size, morphology, coloration, feeding ecology, and/or habitat occupancy. Although morphotypes that have very divergent spawning seasons should become genetically segregated, genetic differentiation, in most cases, has been weak. Thus, results to date have suggested that Arctic Char morphotype separation has been driven largely by the environmentally mediated phenotypic plasticity of the species, with differentiation between morphotypes having commenced too recently to generate substantial genetic drift. Here we used the major histocompatibility (MH) class II genes in an attempt to isolate sympatric Arctic Char morphotypes known to be ecologically differentiated. These morphotypes are from postglacial lakes in both Siberia and eastern Canada, and differ in either diet, habitat occupancy, or both. The MH Class II allelic polymorphism was significantly different between morphotypes. This suggested there is differential heritable adaptation to the natural selection exerted by pathogens unique to each ecological niche within each lake.

Received September 13, 2012; accepted November 19, 2013

ACKNOWLEDGMENTS

Support for the work was provided by Fisheries and Oceans Canada, the Gander River Management Association, Natural Science and Engineering Research Council of Canada Discovery Grant numbers 217529-2008 to B.D. and 155928-2010 to M.P., and the Russian Foundation for Basic Research (project number 11-04-00109): Program of Fundamental Studies of the Presidium of Russian Academy of Sciences “Biodiversity” to S.A. We also thank A. Walsh, R. Noel, B. Gillingham, G. Furey, M. Bloom, M. Shears, N. Sinnatamby, V. Samusenok, A. Matveev, I. Knizhin, A. Yur’ev, and A. Vokin for field collection and laboratory analyses of the samples. Nucleotide sequence data reported are available in the GenBank databases under the accession numbers: EF450348–EF450407 and EU159605–EU159630.