Genetic population structure of the Greater Bilby Macrotis lagotis, a marsupial in decline

Abstract

The Greater Bilby has shown a rapid decline in range during this century and now occupies only a small isolated area in south-western Queensland (QLD) and a larger, but mostly low-density area in the north-western deserts of the Northern Territory (NT) and Western Australia (WA). We have examined variation in the control region of mitochondrial DNA (mtDNA) and at nine microsatellite loci in order to investigate the extent of current and historical subdivision across the species range, and to provide a preliminary assessment of genetic structuring and mating system on a finer scale within the QLD population. Both mtDNA and microsatellite loci had substantial variation within and among populations, with mtDNA divergence being greater between QLD and NT than between NT and WA. The QLD population had two unique and divergent mtDNA lineages, but there was no evidence for strong phylogeographical structure across the range. The available evidence suggests that the bilby should be considered as a single Evolutionarily Significant Unit consisting of multiple Management Units. Augmentation of the remnant QLD population from the NT does not appear necessary at this stage, at least not on genetic grounds. Finer-scale analysis of microsatellite variation for two QLD colonies revealed a deficiency of heterozygotes and significantly greater relatedness within than between colonies. However, structuring was observed only for males; relatedness values for females did not depart from those expected under panmixia. Parentage exclusion analysis for one colony allowed the construction of a partial pedigree which indicated strong polygyny, with one male fathering all but one of the eight offspring assigned. The extent to which fine-scale genetic structuring and differences between sexes is due to sex-biased dispersal vs. effects of mating system remain to be determined.

Phylogeographic variation in the quokka, Setonix brachyurus (Marsupialia: Macropodidae): implications for conservation

“…Mitochondrial haplotype diversity (H = 1.00) was very high, but nucleotide diversity was low (π = 0.028). These values are again comparable to intraspecific values for other Australian mammals (e.g., Pope et al, 1996;Moritz et al, 1997). The lack of fixed allozyme differences and sharing of mtDNA nucleotide substitutions among sampled populations is consistent with similar histories up until the end of the Pleistocene.…”

Reintroduction of the greater bilby, Macrotis lagotis (Reid) (Marsupialia : Thylacomyidae), to northern South Australia: survival, ecology and notes on reintroduction protocols

“…Home ranges of males overlapped considerably, indicating an absence of defended territories, but the extent of overlap may have been influenced by the size of the exclosure. Bilbies were found to maintain strict dominance hierarchies in captivity (Johnson and Johnson 1983), and Moritz et al (1997) found strong polygyny in a Queensland population study. Dominance in wild male bilbies may be maintained through temporal rather than spatial avoidance.…”

Genetic variation and structuring in the threatened koala populations of Southeast Queensland

“…Macrotis lagotis [Moritz et al 1997]; Petrogale lateralis [Eldridge et al 1999]). Consistent with the expectation that island populations show reduced genetic diversity compared to mainland populations due to isolation and the susceptibility of relatively small populations to the effects of genetic drift (Frankham 1997), the genetic diversity on North Stradbroke Island was significantly lower than in the mainland Southeast Queensland koalas.…”