Population processes in an early successional heathland: a case study of the eastern chestnut mouse (Pseudomys gracilicaudatus)
Creators: name: Pereoglou, Felicia
Publisher: name: The Australian National University
Year: 2016
Subjects: fire
heathland
small mammals
pseudomys gracilicaudatus
eastern chestnut mouse
early successional habitat
refuge sites
nesting behaviour
radiotelemetry
landscape ecology
site occupancy
landscape genetics
population genetics
population dynamics
recruitment

description: The eastern chestnut mouse (Pseudomys gracilicaudatus) has been described as a fire specialist inhabitant of early successional heathland. There is a global concern that changes to natural disturbance regimes will place early successional habitat specialists like the eastern chestnut mouse at an increased risk of extinction by altering landscape patterns of habitat suitability. Despite this concern, the fundamental population processes that occur in early successional heathlands are currently unknown for many species. This thesis comprises four research articles that investigate the underlying mechanisms used by a species to persist in this spatially and temporally variable habitat. To determine which features of burned heath were selected as refuge sites, 58 individuals of the eastern chestnut mouse were radio-tracked. Animals preferentially selected multiple aboveground shelter sites characterised by tall, dense vegetation with structural features present. The eastern chestnut mouse was ephemeral and non-gregarious in its refuge use. Refugia were highly flammable. These findings imply land management should ensure retention of vegetation structure on the ground layer and dense habitat patches in burned areas to assist with population viability. A long-term monitoring data set was analysed to evaluate the effects of landscape structure, fire history, and site-level habitat quality on site occupancy in an early successional heathland. Eastern chestnut mouse site occupancy was strongly related to patch area and landscape heterogeneity. There was no direct effect of recent or historical fire, but site occupancy was associated with dead shrubs in the understory and rock cover on ground layer. Small mammal species associations did not conform to that predicted by contemporary ecological theory. The findings suggest landscape configuration and continuity be used to guide survey work and fire regimes to promote eastern chestnut mouse population growth should retain critical habitat features rather than be based on temporal rates of successional stages. To examine population genetic structure, dispersal patterns and the effects of landscape variation on dispersal of an early successional specialist, microsatellite markers were used to genotype tissue obtained from 287 individuals. Differentiation between sites fitted an isolation-by-distance pattern. There was spatial autocorrelation of multilocus genotypes to a distance of 2–3 km with no evidence for sex-biased dispersal. Recently burned vegetation had greater conductance for gene flow than unburnt habitat, but variation in habitat quality between vegetation types and occupied patches had no effect on gene flow. These findings indicate a ‘generalist’ dispersal strategy is advantageous for post-fire specialists to access early successional vegetation. To quantify survival, recruitment and immigration rates in populations of the eastern chestnut mouse, demographic modelling and genetic assignment tests were applied to two years of mark–recapture data. Survival and recruitment rates varied across sites. Survival was influenced by fire history and elements of habitat structure affected by fire. Immigration contributed very little to recruitment compared to local reproduction, suggesting populations are demographically discrete at this post-fire stage. Demographic and genetic data were consistent; sites with high recruitment also had higher genetic diversity and lower temporal genetic structure, consistent with reduced genetic drift. This thesis provides an investigation of the strategies used by the eastern chestnut mouse to persist in an early successional heathland and adds significant new knowledge on the critical resources, predictors of occurrence, population genetics, and demographic rates of the species. The major implication of this research is that a predicted increase in fire occurrence will potentially influence the viability of populations of the eastern chestnut mouse by promoting gene flow but concomitantly decreasing critical habitat features that support site occupancy, increase survival rates, and provide nesting refugia. Furthermore, landscape continuity has a secondary influence population processes and this must be considered in conjunction with the disturbance regime to inform management actions.