Reproductive Photoresponsiveness: Selection for Genetic Variants

(Peromyscus leucopus)

In the figures is shown the change in the frequency of reproductive photoresponsiveness in P leucopus after three-four generations selected FOR and AGAINST that trait. Approximately 50% of the parental generation (P) were responsive, ie experienced reduced reproductive abilities when exposed to a short photoperiod. Selected photoresponsive mice were bred to produce the F₁ generation, and in like manner an subsequent generations were produced. Similarly, sequential generations were produced from parents to be non-responsive to photoperiods.

Peromyscus leucopus from Michigan (Heideman and Bronson, 1991)

Peromyscus leucopus from Williamsburg, Virginia (Heideman et al., 1999)

This is a clear demonstration that both of these populations of Peromyscus leucopus manifest selectable genetic variation for photoperiod responsiveness. It is noteworthy that continued selection for responsiveness or non-responsiveness fails to produce groups of mice all of whom expressing one phenotype or the other. Mechanisms must exist to prevent full penetrance of the genetic trait to ensure a level of phenotypic variability necessary to accommodate the variations in seasonal severity from year to year.

Heideman PD, Bronson FH. 1991. Characteristics of a genetic polymorphism for reproductive photoresponsiveness in the white-footed mouse (Peromyscus leucopus). Biol Reprod 44:1189-1196.

Heideman PD, Bruno TA, Singley JW, Smedley JV. 1999. Genetic variation in photoperiodism in Peromyscus leucopus: geographic variation in an alternative life-history strategy. J Mammal 80:1232-1242.