Are baculum size and allometry a response to post-copulatory sexual selection in promiscuous males of the house mouse?

Abstract

Great genital variation occurs across animal species, likely reflecting the operation of sexual selection. We quantified bacular, testicular, and vesicular size, variation, and allometry in house mice (Laurentii in: Mus musculus Linnaeus, Systema naturae 10th ed, Salvii, Stockholm, 1758) from the western Carpathians (Slovakia). We investigated whether baculum size is related to size of reproductive organs (testicular length and width, and vesicular length), and with body size (head-and-body length), which is not directly involved in reproduction. The corrected coefficient of variation (CV’) for all bacular, testicular, and vesicular traits was significantly higher than non-sexual somatic traits. The negative allometry and weak relationship between baculum size and head-and-body length obtained in presented study (OLS regression) suggest that the Mus musculus baculum is under stabilizing selection. We also assumed that penile width as related to bacular thickness could be a reliable indicator of quality during copulation.