| Summary: | I searched for quantitative trait loci (QTL) affecting fitness traits in crosses between the Nauyuk Lake and Fraser River strains of Arctic charr ('Salvelinus alpinus'). A comparative mapping approach using microsatellite loci demonstrated that several chromosomal regions influencing upper thermal tolerance and body size have been conserved in Aredc charr based on previous work with rainbow trout ('Oncorhynchus mykiss'). Thus, genes underlying fitness QTL may antedate the divergence of these two species. QTL for condition factor and relative gonad size (gonadosomatic index) were also identified. In addition, pairs of homeologues (ancestrally duplicated chromosomal segments) have maintained similar functions in Arctic charr since the evolution of salmonids from a tetraploid ancestor 100-25MYA. However, co-occurrence of body size and thermal tolerance QTL on the same linkage group, and high phenotypic correlations between the two traits, suggest that associated genes control a more basic physiological function like metabolism.
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