Is morphometric variation associated with teat-number differences in Antechinus agilis and A. swainsonii ? Observations from the Otway Ranges, Victoria

That there is intraspecific variation in teat-number in Antechinus agilis (agile antechinus) and A. swainsonii (dusky antechinus) has been known for a long time. Our aim was to determine whether other key morphometric traits differed among individuals with different numbers of teats. External body dimensions and pelage characteristics were measured on live individuals and compared. Within-species variation in some external body dimensions (tail, pes, and snout-vent length) coincided with teat-number differentiation in both antechinus species in the Otway Ranges, Victoria. Disparities in pelage colour and markings were apparent between A. agilis 6- and 10-teat phenotypes, but were not obvious among A. swainsonii teat phenotypes. Although small sample sizes obviated statistical analysis, we tentatively concluded that female A. agilis with 7, 8, or 9 teats in the Otway Ranges probably displayed morphometric and pelage characteristics intermediate between those of 6- and 10-teat individuals. A comparison of morphometric traits among 6-teat A. agilis from different geographic areas (Otways, Portland and Wilsons Promontory) also revealed some variation. This result was consistent with an expectation of clinal variation in external morphology among antechinus. Overall, this study indicates that localized disparities that are associated with teat-number, as well as clinal differences occurring over large geographic distances, contribute to intraspecific variation in external morphology in antechinus.