New populations of the black-flanked rock-wallaby (Petrogale lateralis) from the Little Sandy Desert and Murchison, Western Australia

During two independent fauna surveys, rock-wallaby (Petrogale) scats were recorded from caves located outside the current known Petrogale distribution. Scats collected from Desert Queen Baths (Little Sandy Desert, Western Australia, 2012), and the Barr Smith Range (Murchison, Western Australia, 2015) were genetically analysed and a follow-up motion camera survey confirmed an extant rock-wallaby population at Desert Queen Baths. The combination of sampling techniques overcame the detection difficulties associated with rare and cryptic taxa, and together were important in establishing the presence of Petrogale lateralis from regions where the species has been poorly documented. At both locations, P. lateralis scats were recorded from deep caves situated close to permanent water, reflecting the species’ physiological constraints in the arid zone. These records represent significant range extensions of a highly threatened macropod.

Conservation of genetic uniqueness of populations may increase extinction likelihood of endangered species: the case of Australian mammals

BACKGROUND

As increasingly fragmented and isolated populations of threatened species become subjected to climate change, invasive species and other stressors, there is an urgent need to consider adaptive potential when making conservation decisions rather than focussing on past processes. In many cases, populations identified as unique and currently managed separately suffer increased risk of extinction through demographic and genetic processes. Other populations currently not at risk are likely to be on a trajectory where declines in population size and fitness soon appear inevitable.

RESULTS

Using datasets from natural Australian mammal populations, we show that drift processes are likely to be driving uniqueness in populations of many threatened species as a result of small population size and fragmentation. Conserving and managing such remnant populations separately will therefore often decrease their adaptive potential and increase species extinction risk.

CONCLUSIONS

These results highlight the need for a paradigm shift in conservation biology practise; strategies need to focus on the preservation of genetic diversity at the species level, rather than population, subspecies or evolutionary significant unit. The introduction of new genetic variants into populations through in situ translocation needs to be considered more broadly in conservation programs as a way of decreasing extinction risk by increasing neutral genetic diversity which may increase the adaptive potential of populations if adaptive variation is also increased.

Population structure and genetic diversity of the black-footed rock-wallaby (Petrogale lateralis MacDonnell Ranges race)

Genetic diversity is a critical determinant of the persistence of populations because it enables animals to evolve and adapt to environmental change. Black-footed rock-wallabies (Petrogale lateralis MacDonnell Ranges race), or warru, once occupied virtually all suitable habitat within the arid zone of central Australia. However, only two metapopulations now remain in the southern portion of this race’s range (South Australia) and a recovery program has involved both in- and ex-situ conservation initiatives. To establish whether genetic factors such as inbreeding may be inhibiting population recovery, the current study examined the population structure and genetic diversity of animals in the three largest-known extant colonies using six polymorphic microsatellite loci. Bayesian and frequency-based assignment tests revealed substantial population structuring (pairwise FST values 0.122–0.278), congruent with geographically distinct colonies. There was some evidence of dispersal, with two migrants identified across two colonies, but little evidence for extensive interbreeding among colonies. Population substructure was evidenced by high values of FIS in one colony. All populations possessed relatively high levels of genetic diversity (allelic richness: 5.1–7.5, heterozygosity: 0.70–0.72). On the basis of a genetic analysis of parentage, approximately half of all males and females in the known metapopulations produced offspring. This has likely contributed to the retention of genetic diversity across colonies. These findings have implications for the management of both the in- and ex-situ warru populations.