Data from: The phenotypic correlates and quantitative genetics of masculinization in the rodent, Octodon degus

In some mammals female characteristics have been shown to depend in part
on the intrauterine position during development of female fetuses relative
to male fetuses. Females developing in close proximity to males show
behavioural, physiological and life history characteristics that are
masculinized. With the exception of one inconclusive study, nothing is
known of the genetic basis of this phenomenon. In this paper we reported
an analysis of the quantitative genetic basis of masculinization, as
indicated by the anogenital distance (AGD) at birth and weaning, in the
rodent Octodon degus. Because AGD is related to weight we included a
genetic analysis of pup weight at birth and weaning. Pairwise correlations
showed that AGD at birth varied negatively with litter size and
parturition number but positively with weaning AGD, birth weight, dam AGD
and percentage of males in the litter. AGD at weaning varied similarly
except that it tended to vary positively with litter size. Genetic
(co)variances of AGD at birth and weight at birth differed in females and
males. In females the best genetic model included substantial effects of
direct additive, additive maternal and a negative additive genetic
covariance between these two. In males variances were small and there was
difficulty in discriminating between additive maternal and common
environmental variances. By weaning genetic (co)variances had somewhat
declined in weight and were not statistically significant in AGD in either
sex. This paper showed the occurrence of both phenotypic and genetic
components in masculinization with effects being greater in females.