Abstract
Sexual dimorphism in anatomical traits has been widely studied in animals. Although pelvis dimorphism was mostly studied in humans, it occurs also in many other mammalian species. Here, we investigated sexual dimorphism in the pelvis of the bank vole Myodes glareolus using individuals with known sex and reproductive status of females (parous vs nulliparous). The analyses revealed that the size and shape of pelvis differed significantly between sexes, as well as between nulliparous and parous females. In comparison with males, females had a significantly longer pelvis and pubis bones and a longer obturator foramen length, but a smaller pubis width. Interestingly, the difference between parous and nulliparous females resembles that between females and males: parous females had bigger pelvis, which probably resulted from changes during pregnancy and after birth. Left bones were on average larger than right ones, but the magnitude of directional asymmetry was not different between sex and reproduction group. Moreover, we noticed that fluctuating asymmetry of pelvis and pubis length was higher in females than in males and higher in parous than in nulliparous females, what is presumably associated with locomotor performance. A discriminant function analysis performed for the four bone size traits showed that the traits can be effectively used for a nearly perfect recognition of sexes and also a quite reliable recognition of the reproductive status of females.
Highlights
Sexual dimorphism in anatomical traits has been widely studied in animals
We present in detail only the results from mixed models and focus on the three parameters of interest
The simple models indicated a small but significant directional asymmetry, but we will discuss the issue in the context of more complex models, which take into account the differences between sex-andreproductive status groups (SRS) and two sampling years
Summary
Among studies on osteological traits, sexual dimorphism of the pelvis (os coxa) has attracted the attention of several authors studying various mammalian species (Iguchi et al 1995; Schutz et al 2009a), including rodents (Trejo and Guthmann 2003; Berdnikovs et al 2007; Balčiauskienė and Balčiauskas 2009a). Some of those studies have focused on pelvic development (Polaćek and Novotny 1969; Uesugi et al 1992) and others on morphology (St. Clair 2007; Schutz et al 2009a). With regard to size and shape of the pelvis, exists even where there is a small difference in size between males and females (Schutz et al 2009a)
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