Habitat utilization patterns of sympatric populations of Pseudomys gracilicaudatus and Rattus lutreolus in coastal heathland: A multivariate analysis

Abstract Habitat usage characteristics of two species of native murid rodents, Pseudomys gracilicaudatus and Rattus lutreolus were investigated on an area of coastal heathland at Myall Lakes National Park. A grid of 151 trap stations comprising 17 traplines was positioned across a mosaic of habitats. At each trap station 19 structural vegetation and physical variables known to affect the microdistribution of small mammals were measured. Multivariate statistical procedures identified those microhabitat variables that contribute to individual species' habitat use and habitat partitioning, and reduce potential competition for space. Cluster analysis classified trap stations into one of six habitat types that were mapped on the study area, identifying a heterogeneous assemblage of interlocking habitats. The pattern is a consequence of topographic variation on the site and, to a lesser extent, its fire history. Trapping results show P. gracilicaudatus and R. lutreolus exhibit similar macrohabitat selection, preferring topographically low habitats, with both species predominantly occupying short dense heath with dense sedge cover. The high overlap in macrohabitat use is greatly reduced when considered trap station by trap station, so that discriminant function and multiple regression analyses demonstrate marked microhabitat selection. Elevation was a highly significant variable, accounting for 41% and 27% of the variance in the habitat used by P. gracilicaudatus and R. lutreolus, respectively. This variable represents a soil moisture gradient that determines changes in the floristic and structural components of the biotic environment. Two other structural vegetation variables and vegetation height contributed 30% of the variance in P. gracilicaudatus distribution. Sedge cover was found to be significant and explained 13% of the variance in R. lutreolus distribution. Within-habitat separation was explained best with a linear combination of variables in a discriminant function, rather than by any single variable. Differential microhabitat selection, interference competition and diet separation appear to be the major factors facilitating coexistence of these two species.     

Environment predicts repeated body size shifts in a recent radiation of Australian mammals*

Closely related species that occur across steep environmental gradients often display clear body size differences, and examining this pattern is crucial to understanding how environmental variation shapes diversity. Australian endemic rodents in the Pseudomys Division (Muridae: Murinae) have repeatedly colonized the arid, monsoon, and mesic biomes over the last 5 million years. Using occurrence records, body mass data, and Bayesian phylogenetic models, we test whether body mass of 31 species in the Pseudomys Division can be predicted by their biome association. We also model the effect of eight environmental variables on body mass. Despite high phylogenetic signal in body mass evolution across the phylogeny, we find that mass predictably increases in the mesic biome and decreases in arid and monsoon biomes. As per Bergmann's rule, temperature is strongly correlated with body mass, as well as several other variables. Our results highlight two important findings. First, body size in Australian rodents has tracked with climate through the Pleistocene, likely due to several environmental variables rather than a single factor. Second, support for both Brownian motion and predictable change at different taxonomic levels in the Pseudomys Division phylogeny demonstrates how the level at which we test hypotheses can alter interpretation of evolutionary processes.     

Range‐wide genetic structure of a cooperative mouse in a semi‐arid zone: Evidence for panmixia

Landscape topography and the mobility of individuals will have fundamental impacts on a species’ population structure, for example by enhancing or reducing gene flow and therefore influencing the effective size and genetic diversity of the population. However, social organization will also influence population genetic structure. For example, species that live and breed in cooperative groups may experience high levels of inbreeding and strong genetic drift. The western pebble‐mound mouse (Pseudomys chapmani), which occupies a highly heterogeneous, semi‐arid landscape in Australia, is an enigmatic social mammal that has the intriguing behaviour of working cooperatively in groups to build permanent pebble mounds above a subterranean burrow system. Here, we used both nuclear (microsatellite) and mitochondrial (mtDNA) markers to analyse the range‐wide population structure of western pebble‐mound mice sourced from multiple social groups. We observed high levels of genetic diversity at the broad scale, very weak genetic differentiation at a finer scale and low levels of inbreeding. Our genetic analyses suggest that the western pebble‐mound mouse population is both panmictic and highly viable. We conclude that high genetic connectivity across the complex landscape is a consequence of the species’ ability to permeate their environment, which may be enhanced by “boom‐bust” population dynamics driven by the semi‐arid climate. More broadly, our results highlight the importance of sampling strategies to infer social structure and demonstrate that sociality is an important component of population genetic structure.     

Responses of two species of heathland rodents to habitat manipulation: Vegetation density thresholds and the habitat accommodation model

The abundance of two native rodent species, Rattus lutreolus and Pseudomys gracilicaudatus, has been shown to correlate with vegetation density in coastal wet heath. Fox's habitat accommodation model relates relative abundances of such small mammal species to heathland vegetation regeneration following disturbance. Implicit in the model is recognition that it is successional changes in vegetation, not time per se, that drives the responses of small mammal species along a regeneration axis. Using a brush‐cutter we deliberately removed approximately 85% of vegetation around trapping stations and recorded significant reductions in the abundance of both P. gracilicaudatus (an earlier‐stage colonizing species) and R. lutreolus (a late seral‐stage species). A significant decrease in the abundance of only the latter had been demonstrated previously when 60–70% of the vegetation had been removed. Following the brush‐cutting both species re‐entered the mammalian secondary succession at different times, first P. gracilicaudatus followed by R. lutreolus after the vegetation cover thresholds of each species had been reached. The impact of this habitat manipulation experiment was to produce a retrogression of the small mammal succession, experimentally demonstrating causality between changes in vegetation density and subsequent small mammal habitat use.     

Microsatellite primers for the Western Pebble‐mound Mouse (Pseudomys chapmani) that show cross amplification for other species of Australian rodent

We describe 12 dinucleotide and one tetranucleotide microsatellite loci for the Western Pebble‐mound Mouse (Pseudomys chapmani) that can be amplified with the polymerase chain reaction. All primers produced clear and highly polymorphic amplification patterns containing between seven and 14 alleles and with high expected heterozygosities. The amplification of these primers across seven related conspecifics makes them useful for population genetic studies and conservation work in several of these species.     

Small mammal succession is determined by vegetation density rather than time elapsed since disturbance

Abstract We examined post‐fire responses of two sympatric Australian rodents, Pseudomys gracilicaudatus and Rattus lutreolus, as coastal wet heath regenerated following two high intensity wildfires. Pseudomys gracilicaudatus, an early serai‐stage species, recolonized an area burnt in August 1974 after one year, but took only 3 months to recolonize another area following a wildfire in October 1994. Rattus lutreolus, a late serai‐stage specialist, took approximately 3.6 years to recolonize following wildfire in August 1974, but had recolonized after only 4 months following wildfire in October 1994. We suggest that this apparent anomaly is associated with the rate of recovery of vegetation density. When the relative abundance of each species was plotted as a function of vegetation density, the trajectories following the two wildfires were concordant. An implicit relationship exists between time since wildfire and vegetation density. We make this relationship explicit by quantifying cover requirements for each species, and show that it is the resource continuum borne of regenerating vegetation (rather than time per se) that is important in determining the timing of small mammal successional sequences.     

曲霉及其有性型散囊菌的新分类群和新记录种

在收集和分离我国曲霉工作中,发现一个国内新纪录和三个新分类群:1.埃及曲霉,国内新记录。2.合阳曲霉新种,与爪甲曲霉相近,但颜色和具刺不育菌丝有所不同。3.温特曲霉烟色变种,与原变种的主要区别在于颜色为蓝灰色并具异常膨大的梗基。4.瘤突散囊菌新种,其子囊孢子的纹饰独特,凸面具粗疏瘤状突起。     

Artificial boulderfield yields a surprise: The Smoky Mouse in Kosciuszko National Park,Australia

Spoil dumps in the subalpine and montane environments of Kosciuszko National Park in far south‐eastern Australia are modified landscapes which in the past were considered to have little faunal value. Recent finds (2010–2011) of the critically endangered Mountain Pygmy‐possum (Burramys parvus) have resulted in a reconsideration of the importance of such landscapes to fauna. Such re‐evaluation has been translated into on‐ground actions, including the construction of an artificial boulderfield on one spoil dump as habitat targeting Mountain Pygmy‐possum in rehabilitation works. Trapping 7 and 19–20 months, respectively, after these works has so far not recorded this Pygmy‐possum. However, it led to the discovery of another critically endangered species, the Smoky Mouse (Pseudomys fumeus). Two males (with three recaptures) and one female were captured in 250 trapnights in November 2015 and an additional male in 600 trapnights in December 2015. The capture of this enigmatic species is highly significant as it is the first live capture of the species in the park and it is only the second locality in which live captures have been made in New South Wales since 2001. The location of the Smoky Mouse in spoil dumps further emphasises how these areas provide existing and potential habitat for native fauna species.