Social organisation and population genetics of the threatened great desert skink, Liopholis kintorei

The great desert skink, Liopholis kintorei, is a listed Threatened species with a patchy distribution across the arid zone of central and western Australia. It is a member of a group of Australian lizards, the Egernia group, recently adopted as model species for the early evolution and maintenance of vertebrate sociality. Most Egernia group species that live in stable, kin-based groups utilise pre-existing shelter sites such as rock crevices, but L. kintorei is unique in that individuals cooperatively construct and maintain extensive burrow systems that house kin. I researched aspects of the behavioural ecology and social structure of L. kintorei, using field-based methods and molecular techniques. I captured individuals from a study population at the Australian Wildlife Conservancy’s Newhaven Sanctuary in central Australia, at which a total of seven months of fieldwork was carried out over three years. The results of my research are discussed in the context of the evolution and maintenance of kin-based social living, with comments on the implications for the species’ conservation in central Australia. Social organisation was investigated by trapping lizards at their burrows over the three years and through molecular analyses of relatedness within and among groups. Like other members of the Egernia group, L. kintorei has a complex social structure. Generally, I found that L. kintorei at Newhaven live in groups of related individuals, although there is considerable variation among groups in their size, structure and stability across years: some groups involved male–female pairs together for a single season, while one group contained a mated pair and offspring from three separate seasons. It is possible that L. kintorei social groups are not so constrained by habitat availability because of their ability to construct their own shelter sites. However, the importance of stable food sources in the unpredictable desert environment could maintain group living in this species because tolerance among group members would allow them to share such resources rather than compete among kin. Through broader-scale genetic analyses, I found evidence of male-biased dispersal, with no genetic structure among males, but significantly high relatedness among females at short distance classes. This was supported by the recapture data for males, showing a higher level of movement among burrows than for females. Males were captured, on average, at a higher number of distinct burrows than were females, and the distance between capture points was also higher. There was also sexual head-size dimorphism in this species, with males having longer and broader heads than females, relative to body size. This trait may be maintained in L. kintorei by sexual selection through agonistic encounters among interspecific males. An analysis of genetic differentiation among localities inhabited by L. kintorei across its distribution was also carried out. Utilising mitochondrial and microsatellite loci, we genotyped samples collected from six localities, revealing high levels of differentiation among them. The extent of this differentiation suggests that regions containing this Threatened species should be managed separately, particularly the southeastern locality of Uluru, and this distinctiveness should be recognised if intervention such as translocation or captive breeding is to be undertaken.