Population genetics of the brush-tail possum

The genetic relationships among and within possum populations both throughout New Zealand and on a local scale were examined using allozyme electrophoresis.

Two morphological types were introduced to New Zealand: smaller, grey possums from mainland Australia; and larger, black possums from Tasmania. These two main stocks are non-randomly distributed in New Zealand; relationships were found between stock type, genotype, coat colour, and climatic variables.

The genetic structure of a local possum population (in the Orongorongo Valley, near Wellington) was analysed using F-statistics. Significant geographic structuring occurred over distances of several kilometres; samples separated by 2 km were essentially panmictic. Effective population size was very approximately estimated by genetic and ecological methods to be of the order of 103-104. The significant level of inbreeding found within local populations was consistent with consanguineous mating, presumably resulting from the non-dispersal of a high proportion of young (particularly female) possums.