How high is your hummock? The importance of T riodia height as a habitat predictor for an endangered marsupial in a fire-prone environment

Empirical landscape genetic comparison of single nucleotide polymorphisms and microsatellites in three arid-zone mammals with high dispersal capacity

Landscape genetics is increasingly transitioning away from microsatellites, with single nucleotide polymorphisms (SNPs) providing increased resolution for detecting patterns of spatial-genetic structure. This is particularly pertinent for research in arid-zone mammals due to challenges associated with unique life history traits, such as boom-bust population dynamics and long-distance dispersal capacities. Here, we provide a case study comparing SNPs versus microsatellites for testing three explicit landscape genetic hypotheses (isolation-by-distance, isolation-by-barrier, and isolation-by-resistance) in a suite of small, arid-zone mammals in the Pilbara region of Western Australia. Using clustering algorithms, Mantel tests, and linear mixed effects models, we compare functional connectivity between genetic marker types and across species, including one marsupial, Ningaui timealeyi, and two native rodents, Pseudomys chapmani and P. hermannsburgensis. SNPs resolved subtle genetic structuring not detected by microsatellites, particularly for N. timealeyi where two genetic clusters were identified. Furthermore, stronger signatures of isolation-by-distance and isolation-by-resistance were detected when using SNPs, and model selection based on SNPs tended to identify more complex resistance surfaces (i.e., composite surfaces of multiple environmental layers) in the best-performing models. While we found limited evidence for physical barriers to dispersal across the Pilbara for all species, we found that topography, substrate, and soil moisture were the main environmental drivers shaping functional connectivity. Our study demonstrates that new analytical and genetic tools can provide novel ecological insights into arid landscapes, with potential application to conservation management through identifying dispersal corridors to mediate the impacts of ongoing habitat fragmentation in the region.

Diurnal sheltering preferences and associated conservation management for the endangered sandhill dunnart, Sminthopsis psammophila

Dasyurids are small mammals that can conserve energy and water by using shelters that insulate against extreme conditions, prevent predation, and facilitate torpor. To quantify the diurnal sheltering requirements of a poorly known, endangered dasyurid, the sandhill dunnart, Sminthopsis psammophila, we radiotracked 40 individuals in the Western Australian Great Victoria Desert between 2015 and 2019. We assessed the effect of habitat class (broad habitat features), plot-level (the area surrounding each shelter), and shelter characteristics (e.g., daily temperature ranges), on shelter selection and sheltering habitat preferences. Two hundred and eleven diurnal shelters (mean of 5 ± 3 shelters per individual) were located on 363 shelter days (the number of days each shelter was used), within mature vegetation (mean seral age of 32 ± 12 years postfire). Burrows were used on 77% of shelter days and were typically concealed under mature spinifex, Triodia spp., with stable temperature ranges and northern aspects facing the sun. While many burrows were reused (n = 40 across 175 shelter days), spinifex hummock shelters typically were used for one shelter day and were not insulative against extreme temperatures. However, shallow scrapes within Lepidobolus deserti hummock shelters had thermal advantages and log shelters retained heat and were selected on cooler days. Sminthopsis psammophila requires long-unburned sheltering habitat with mature vegetation. Summer fires in the Great Victoria Desert can be extensive and destroy large areas of land, rendering them a key threat to the species. We conclude that the survey and conservation of S. psammophila requires attention to long-unburned, dense lower stratum swale, sand plain, and dune slope habitats, and the tendency of S. psammophila to burrow allows the species to survive within the extreme conditions of its desert environment.

Predators, prey or temperature? Mechanisms driving niche use of a foundation plant species by specialist lizards

Foundation species interact strongly with other species to profoundly influence communities, such as by providing food, refuge from predators or beneficial microclimates. We tested relative support for these mechanisms using spinifex grass (Triodia spp.), which is a foundation species of arid Australia that provides habitat for diverse lizard communities. We first compared the attributes of live and dead spinifex, bare ground and a structurally similar plant (Lomandra effusa), and then tested the relative strength of association of two spinifex specialist lizard species (Ctenophorus spinodomus and Ctenotus atlas) with spinifex using a mesocosm experiment. Temperatures were coolest within spinifex compared to bare ground and Lomandra. Invertebrate abundance and the threat of predation were indistinguishable between treatments, suggesting temperature attenuation may be a more important driver. Overall, the dragon C. spinodomus preferred live over dead spinifex, while the skink C. atlas preferred dead spinifex, particularly at warmer air temperatures. However, both species displayed individual variability in their use of available microhabitats, with some individuals rarely using spinifex. Our results provide an example of temperature attenuation by a foundation species driving niche use by ectothermic animals.

Small marsupial, big dispersal? Broad- and fine-scale genetic structure of an endangered marsupial from the Australian arid zone

The irregular nature of rainfall in the Australian arid and semiarid zones results in a heterogeneous distribution of resources in both time and space. The mammal species that reside in these regions are uniquely adapted to these climatic conditions, often occurring in naturally low densities and increasing significantly in numbers following major rainfall events. We investigated how these adaptations may influence genetic diversity and gene flow across the landscape in an endangered semiarid/arid-zone marsupial, the sandhill dunnart (Sminthopsis psammophila), from three known populations in southern Australia. Analyses of mitochondrial control region (CR) sequences and microsatellite loci revealed that S. psammophila had maintained similar levels of genetic diversity to other sympatric Sminthopsis species despite its endangered status. There was no evidence for significant phylogeographic structure within the species, but each population was genetically differentiated, based on the frequency of microsatellite alleles and CR haplotypes, suggesting that they should be considered as distinct Management Units for conservation. At a fine spatial scale, no significant genetic structure or sex-biased dispersal was detected within a study site of 240km2. These findings suggest that both sexes are highly mobile, which allows individuals to locate localised resource patches when they become available. We detected evidence of a genetic bottleneck within the population, possibly caused by a recent drought. Our study highlights the importance of maintaining connectivity across the landscape for semiarid- and arid-zone species to enable them to track resource pulses and maintain genetic diversity.

Multi-scale habitat associations of the black-footed rock-wallaby in north-western South Australia

Context Research on species’ habitat associations is strengthened if it combines coarse-grained landscape data with finer-scale parameters. However, due to the effort required to measure fine-scale parameters, studies on threatened species that unite these two scales remain relatively rare. Aim This study aimed to undertake a multi-scale analysis of the habitat association of the threatened Petrogale lateralis (MacDonnell Ranges race) in the Anangu Pitjantjatjara Yankunytjatjara (APY) Lands, South Australia. Method Analyses were conducted at four spatial scales: (1) across the Central Ranges IBRA Region (regional scale); (2) on hills in the APY Lands at which P. lateralis is extant and extinct (site scale); (3) at ‘core’ and ‘non-core’ areas within those hills (hillside scale); and (4) at rocky refuges. The maximum entropy approach through the software MaxEnt was used for the analysis at the regional scale. At the remaining scales, fieldwork was used to collect, and regression modelling to analyse, data. Key results At the regional scale, presence was associated with slope and geology. At the site scale, aspect, rock abundance and habitat type are likely to have facilitated animal persistence at extant sites. At the hillside scale, the aspect, vegetation type and rock complexity of core areas are likely to have contributed to their higher use. Size, exposure and accessibility were significant predictors of the use of rocky refuges. Conclusions All four spatial scales yielded novel information on the habitat associations of P. lateralis, supporting previous researchers’ suggestions that habitat modelling should be conducted at multiple spatial scales. Implications The study exemplifies the utility of combining MaxEnt modelling with fieldwork-derived data. The results may have conservation implications for this threatened race, and may also provide a model for other studies of faunal habitat associations.