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 populat ions of the southern brown bandicoot, Isoodon obesulus, in the south-w est of Western Australia, with a view to determining the possible pres ence of adaptive divergence. Analysis of variance and canonical variat e analysis were employed to examine the variation in body weight, head length, pes length and ear length among six locations. Significant se xual dimorphism was detected for these morphological variables, with m ales being larger than females. Significant geographic variation in ov erall body size and shape was found for both males and females. Correl ations between body size and shape and each of five environmental vari ables (mean annual rainfall, mean maximum summer temperature, mean min imum winter temperature, relative humidity and latitude) were tested. Neither body size nor shape was correlated with any of the five variab les, but both were related to habitat structure, with larger bandicoot s being found in open forest habitats, while smaller bandicoots were f ound among swamp reeds. If the above variation has a genetic basis, th ese differences between locations may represent adaptive divergence an d thus be of importance when formulating a conservation strategy for t his species.