Abstract for presentation at Biodiversity Extinction Crisis Conference - A Pacific Response

With growing numbers of species facing threats to their survival in the wild, the ability to maintain animals in captivity is sometimes seen as their last hope for survival. The large number of animals required for maintaining long-term genetic diversity can present conflicts between optimum breeding for maintenance of genetic diversity and the practicalities associated with managing captive populations.
The red-tailed phascogale, a carnivorous marsupial, only breeds once a year with individuals mating promiscuously for several weeks prior to the death of all the males. Captive breeding programs for this species involve maintaining females in groups through which multiple males are rotated during the breeding season. As such, paternity is unknown for the captive breeding colony, and animals are managed on a group basis. This group management means the rate of genetic diversity loss was unknown, but was likely to be overestimated by the studbook.
Offspring from the 2004 breeding season were genotyped using microsatellite markers that allowed for the determination of paternity and consequently the reproductive success of adults. Multiple paternity was confirmed in 5/11 captive red-tailed phascogale litters. Significant biases in siring success were evident with the heaviest males siring 62% of the young when three males were given breeding access to a group of females. The effective population size was calculated to be 15% of the census population size, and this was three times larger than that observed in the group managed studbook, and three times as large as would be obtained if a single male was placed with the group of females. These results indicate that multiple paternity, and the genotyping of offspring, can provide a means for improving the retention of genetic diversity when practical considerations, such as the need to group house females restrict the optimum genetic management of a population.