Effects of Inbreeding and Social Factors on the Reproduction of Young Female Peromyscus maniculatus bairdii

Abstract

Effects of father-daughter inbreeding and reproductive inhibition among young female deermice ( Peromyscus maniculatus bairdii ) are investigated in this study. Young female deermice were put into four social groups: 1) father-daughter pairs; 2) a proven male and unrelated young female; 3) both parents and a 21-day old daughter; 4) a father, daughter, and unrelated older female. All females in these social groups were examined for seven reproductive parameters until the young females were 180 days old. Father-daughter and unrelated pairs of mice were similar in the number of parous females, age at first reproduction, number of litters per female, offspring per litter, and total offspring per female. Weights of the inbred offspring at two days old were significantly smaller, and survival of offspring to 21 days old was significantly less than of offspring produced by unrelated parents. The effect of the mother and unrelated adult female (Groups 3 and 4) was complete inhibition of reproduction in the young females. While none of the daughters reproduced, both classes of older females continued to reproduce normally. The reproduction of adult females in Groups 3 and 4 was equivalent to that of the young females alone with adult males, except for a lower survival rate among the offspring in the father-daughter groups. These results contradict the model proposed by Skryja (1978) that delayed reproduction of a daughter by her mother may increase the daughter's inclusive fitness.