On the Selective Value of the Alleles Rt and rt in Ephestia kuhniella

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Abstract
The alleles Rt and rt in Ephestia influence testis color; Rt is completely dominant over rt. There is evidence that in nature these genes form a balanced polymorphic system. Viability, speed of development, and mating behavior of Rt Rt, Rt rt and rt rt males were compared by observation of F2 and backcross cultures. Rt rt males were found significantly more frequently in copula than rt rt animals. Rt Rt males do not appear to differ from Rt rt in mating behavior. On the other hand, rt rt males are more viable than Rt rt males. Rt rt animals are equal or possibly superior in viability to rt rt. For speed of development, no significant differences were found. It is concluded that the heterozygote is equal to Rt Rt with respect to mating behavior, to rt rt in viability. Although the heterozygote does not appear to be superior to both homozygotes in any single factor of selective advantage, it would on the whole be superior to both homozygotes, since in every trait it is at least equal to the more favored homozygote.