Geographic variation in size and shape in the southern brown bandicoot, Isoodon obesulus (Peramelidae: Marsupialia), in western Australia

Geographic variation in body size and shape was examined among populations of the southern brown bandicoot, Isoodon obesulus, in the south-west of Western Australia, with a view to determining the possible presence of adaptive divergence. Analysis of variance and canonical variate analysis were employed to examine the variation in body weight, head length, pes length and ear length among six locations. Significant sexual dimorphism was detected for these morphological variables, with males being larger than females. Significant geographic variation in overall body size and shape was found for both males and females. Correlations between body size and shape and each of five environmental variables (mean annual rainfall, mean maximum summer temperature, mean minimum winter temperature, relative humidity and latitude) were tested. Neither body size nor shape was correlated with any of the five variables, but both were related to habitat structure, with larger bandicoots being found in open forest habitats, while smaller bandicoots were found among swamp reeds. If the above variation has a genetic basis, these differences between locations may represent adaptive divergence and thus be of importance when formulating a conservation strategy for this species.