Inheritance of Thermal Resistance in Hybrids of Salvelinus fontinalis and S. namaycush

Abstract

The two reciprocal F1 hybrids of brook trout (Salvelinus fontinalis) and lake trout (S. namaycush) had similar times to death on exposure to several lethal high temperatures for a series of acclimation temperatures. These hybrids resembled the brook trout, the more resistant parent, more than the lake trout. The F2 hybrids were intermediate in resistance to the parent species, and the backcrosses intermediate between the F2 hybrids and the respective parents. After acclimation to 5 and 10 C, F2’s and backcrosses arising from the F1 hybrid of brook trout maternal origin were consistently higher in resistance than the F2 and backcrosses arising from the F1 hybrid of lake trout maternal origin. After acclimation to 20 C and above, differences associated with the maternal origin of the F1 hybrid were not found.The number of effective factors segregating was estimated using the techniques of variance component analysis. A genetic model with two codominant factors was found to fit the data for 5 and 10 C acclimation, and one with five factors and dominance of the brook trout factors was found to fit the data for the higher acclimation temperatures.