Molecular ecology and biological control: the mating system of a marsupialpest

Many studies in molecular ecology have focused on the use of repeat DNA mar kers to determine the nature of mating systems in a wide variety of animal species. Whilst these studies typically have focused on important issues su ch as the evolutionary consequences of fitness variation among males, genet ic studies of mating systems are potentially also important because they ca n generate information of significance to wider issues in wildlife manageme nt. For example, genetically modified, sexually transmitted viral diseases have been suggested as potential agents for the control of vertebrate pest species. An understanding of the epidemiology of such agents requires an in timate knowledge of the sexual contact rates between individuals of the tar get species. Here, we report the use of minisatellite DNA profiling to reve al the mating system in two New Zealand populations of the introduced Austr alian brushtail possum. The brushtail possum is New Zealand's most importan t mammalian pest and a species for which control by a sexually transmitted immunocontraceptive has been proposed. Encouragingly, we report considerabl e variation in the reproductive success of males at both study sites, with one male siring offspring from four females in one year (mean no. of offspr ing/reproductively successful male/year at the two sites is 1.95-2.15), whi le many sired none. This bias in the pattern of reproductive success among males will probably facilitate the spread of an immunocontraceptive agent a nd thereby increase the power of this approach to biological control.