Austral Ecology最新文献

Tree hollows are important structural habitat features for secondary cavity-nesting birds, however, there has been limited research on how fire severity and frequency affect hollow abundance. Following a mega-fire on Kangaroo Island during the 2019–2020 Australian bushfire season, we conducted an opportunistic post-fire assessment of the fate of 144 monitored hollows in Eucalyptus cladocalyx and Eucalyptus leucoxylon trees used by endangered glossy black-cockatoos (Calyptorhynchus lathami halmaturinus) and yellow-tailed black-cockatoos (Zanda funerea). We investigated the relationship between burn severity, inter-fire interval, tree species and landscape position on the likelihood of tree hollow loss. We also compared the occupancy of nest boxes by both cockatoo species in fire-affected catchments pre-fire (2015–2017; 59 nest boxes) and post-fire (2020–2022; 52 nest boxes). Surveys revealed that 64.4% of monitored tree hollows within the burnt area were destroyed, as were the trees that contained them. Most monitored tree hollows (76.9%) were in areas that had not experienced fire in >50 years prior to the 2019–2020 fires. Tree hollow loss in 2020 was 29 times greater than the mean annual loss of 1.6% recorded in the 22 years prior. Burn severity, inter-fire interval, landscape matrix and tree species were poor predictors of hollow loss. However, increasing distance from forest edge slightly increased the probability of hollow loss. Post-fire, the proportion of nest boxes used for nesting by glossy black-cockatoos per annum increased to 0.70 ± 0.09, compared to 0.50 ± 0.03 pre-fire. However, the proportion of nest boxes used for nesting by yellow-tailed black-cockatoos per annum remained similar (post-fire 0.32 ± 0.12; pre-fire 0.28 ± 0.05). The mega-fires on Kangaroo Island in 2019–2020 resulted in tree hollow loss on a much larger scale than recorded in the 22 years prior, and subsequently, nest boxes have become an important resource for the endangered glossy black-cockatoo.

This study investigated regional and site level diversity for alpine and subalpine systems. The aim was to assess whether differing analytical methods could track diversity through time. The study was undertaken within Kosciusko National Park in south-eastern Australia (6900 km²) which encompasses most of the alpine zone (~2500 km² or 48% of its occurrence on mainland Australia). Multivariate ordination, species richness and the relationship of diversity to landscape patterns were assessed and considered in relation to changes predicted to impinge upon these systems over coming decades. Species richness had limited capacity to detect predicted changes; however, ordination based on floristic patterns may have more capacity to detect change if adequate replication is applied. Complex patterns across landscapes and at the site level contributed to these analytical challenges. Species richness is commonly used to assess ecosystem status and to provide benchmark values, but it had very limited capacity to do so in the assessed alpine and subalpine ecosystems, including the most threatened. Government agencies often rely heavily on species richness to assess ecosystem change and this urgently needs re-evaluation.

The Carpentarian Pseudantechinus (Pseudantechinus mimulus, Dasyuridae) is a little-known, saxicolous dasyurid marsupial from the Mount Isa Inlier bioregion in Queensland (QLD) and the Gulf Coastal bioregion in the Northern Territory (NT), Australia. A paucity of targeted survey effort across broad swathes of potentially suitable habitat means that the species' distribution and habitat associations are uncertain. This study aimed to (1) refine the contemporary distribution of P. mimulus, (2) determine the landscape and floristic variables that may predict P. mimulus presence, and (3) assess the current conservation status of P. mimulus. We conducted camera trap surveys covering 631 camera stations at 227 independent sites over 4 years for a total of 28 767 trap-nights throughout QLD and NT in known and predicted suitable habitat. Stepwise generalized linear models were used to test the effect of landscape and floristic predictors on P. mimulus presence. The species' contemporary distribution was assessed using a MAXENT species distribution model. We collated a database of 292 records of P. mimulus, including 111 recorded during this study, extending the species' known range in QLD. The proposed holotype location of the Mittiebah Range was surveyed twice during this study but P. mimulus was not recorded. Pseudantechinus mimulus had the highest probability of presence on most non-northerly aspects on metamorphic landforms. Eleven plant taxa had a significant effect on P. mimulus presence. This study provides new evidence for landscape and floristic factors that help predict the presence of P. mimulus. Our results indicate the possibility of two disjunct populations, but large swathes of potential habitat still require additional effort to determine the species' true distribution. Our estimate for area of occupancy partially satisfies a threatened species listing; however, more focused research on population dynamics, trends in habitat quality, and landscape-scale threats is necessary.

Mimicry, the superficial resemblance between organisms of two or more species, is considered a textbook example for natural selection, for which it is assumed that predators are important selective agents. Ant mimicking spiders have received considerable attention in studies on mimicry because they include examples with remarkable, species-specific morphological adaptations. Ant-like behaviours such as erratic locomotory patterns, abdomen bobbing and vertical movements of the first or second pair of legs to imitate antennal movements, are assumed to have evolved before morphological mimicry and may be considered adaptations to general ant resemblance. Species-specific behavioural ant mimicry (behaviour that is only observed in specific ants and imitated by their mimics) was very rarely documented and ant resembling behaviour that repels predator attacks has not been confirmed yet. In this study we report and discuss such species-specific behaviour, a spray display (SD), in the castianeirine spiders Myrmecotypus iguazu (a morphologically accurate mimic of the carpenter ant Camponotus sericeiventris), and M. tahyinandu (a morphologically accurate mimic of C. crassus). The SD consisted of the raising of the cephalothorax and moving of the abdomen ventrally under the cephalothorax, pointing the apex forward, and holding the antennae (ant) or first pair of legs (spiders) at an angle of about 45°–120°. The morphological adaptations that are required to perform the SD and the lack of an alternative explanation for the purpose of this display suggest that the SD has evolved to enhance both general behavioural and morphologically accurate ant resemblance. The two observed Myrmecotypus species may be considered the behaviorally most accurate ant-resembling spiders known to date, as the SD may provide protection against spider- and ant-eating predators at a point in predator interactions where other myrmecomorph spiders may abandon their ant-resembling behaviour.

In Australia, most threatened species translocations conducted into areas where feral predators are present fail to establish viable, self-sustaining populations despite intensive predator control. These translocations are occurring amidst a lack of understanding regarding the conditions required for native species to survive, including predator densities. This study investigated whether population trends of in situ common species could be used as bioindicators to determine the effectiveness of predator management for threatened species protection. We compared changes in capture rates of four small mammals and four reptile species inside and outside a predator-proof reserve for 11 years after cat and fox removal to identify which species responded to cat and fox eradication at various time scales. We only used sites inside the reserve where threatened species had not yet been reintroduced to isolate the effects of cat and fox removal. The effectiveness of these bioindicators was then tested at an unfenced reserve where predators were controlled using baiting, trapping, and shooting. There was a significant increase in the abundance of native rodents (spinifex hopping mouse and Bolam's mouse) inside the fenced reserve compared to outside, however, these differences were not detected in the unfenced reserve possibly due to inadequate predator control or insufficient time for in situ species to recover with sustained predator control. Captures of the introduced house mouse were higher at sites inside the fenced reserve in some years, but the difference was not consistent. Native dunnarts and all four reptile species did not respond consistently over the 11-year time frame at either reserve. Native rodent abundance was the best indicator of effective feral predator control and may provide a useful bioindicator for threatened species management, such as reintroductions.

In many parts of the world, achieving a target of 30% of land managed for conservation under the Kunming-Montreal Global Biodiversity Framework will require the protection of land with a long history of management for production. In newly protected forests, past logging practices will have impacted key aspects of stand structure, including hollow-bearing trees that provide critical habitat for vertebrate fauna. The impacts of past silvicultural practices on hollow density, distribution, type and longevity may necessitate targeted ameliorative actions. We investigated tree hollows in the largest river red gum (Eucalyptus camaldulensis Denh.) forest in the world, which had undergone logging-induced woody thickening prior to being converted to a conservation reserve in 2010. We recorded stem diameters and hollows in living and dead trees in 66 two-hectare plots. Our sites sampled two productivity states and a wide range of total tree densities. On all sites, we found that hollow-bearing tree densities were lower than reference values for unlogged stands and average density had halved relative to reference values. We found no relationship between the density of hollow-bearing trees and total tree density, but we did find a weak positive relationship with site productivity. Larger trees had more hollows, bigger hollows and a greater diversity of hollow sizes. However, of the 1254 hollow-bearing trees recorded, 43% were dead, 48% of the dead trees had been ringbarked. The proportion of hollow-bearing trees that were dead was positively correlated with tree size, with 60% of trees in the largest quartile (>105 cm) recorded as dead. The prevalence of dead hollow-bearing trees suggests that the density and diversity of hollows will continue to decline and ameliorative actions should be considered. These results highlight the need to consider the legacy of past silvicultural practices in the management of newly created conservation reserves.

Drylands are characterized by high spatial variability in resource availability due to sporadic rainfall, topography of the landscape and important effects of animals. Resource availability gradients may trigger patterns in decomposer population abundances and activity, which could affect ecosystem functions such as decomposition. Here, we examined the influence of resource availability gradients on the importance of termites in the decomposition of wood and grass litter. We placed wood blocks and grass litter baits in bags accessible and inaccessible to termites across wood and grass resource gradients as determined by the presence or absence of a top mammalian predator and across topographic gradients during a 9-month period in arid Australia. We hypothesized that grass-eating termite activity would track grass abundance and wood-eating termite activity would track wood abundance. Termites were the predominant decomposition agent at these sites. Termites contributed to 99.5% of wood decomposition and 83.9% of grass decomposition during our study period. For wood, the termite effect was spatially variable and increased with habitat wood availability, which was greatest on dunes and where top predators were absent. However, the contribution of termites to grass litter decomposition did not track grass availability or termite abundance. The highest effects of termites on grass decomposition rates were found in habitats where the absence of top predators led to low grass availability. Our findings highlight how spatial variability in resources in addition to other factors that we do not document but are known to be influenced by the presence of top predators, such as insectivore predation rates, across the landscape could affect ecosystem functions such as decomposition.

Extensive wildfires can have profound impacts on fauna communities by altering the vegetation structure and resource availability. However, unburnt areas within a fire mosaic may be important habitat for wildlife while the surrounding area recovers after fire. To understand the importance of unburnt vegetation for reptiles, we studied community assemblages at 15 burnt and 15 unburnt sites in a subtropical woodland 12 months after a 25 000 ha wildfire. We tested the relative importance of unburnt areas and structural attributes on reptile abundance, richness, and community composition across this landscape. Unburnt areas had higher species richness and diversity, but not overall abundance. Reptile community composition differed significantly between burnt and unburnt areas. Woody debris, which was retained in unburnt areas but depleted in burnt areas, was positively associated with increased reptile diversity and richness. Our results suggest that unburnt areas are vital for maintaining reptile diversity and richness within a woodland landscape after wildfire. These findings demonstrate the importance of ensuring fire management programs retain unburnt patches of vegetation in fire-prone landscapes to sustain reptile communities.

The invasion process and the persistence of invasive species across environments can be explained by their tolerance to stressors, such as salinization. Urochloa arrecta (Poaceae) exhibits high invasive potential and has already established in various natural and artificial aquatic ecosystems. Here, we experimentally evaluate the effects of water salinity on the traits of three exotic populations of U. arrecta derived from naturally occurring populations across a salinity gradient. Specifically, we measured the difference in the number and perimeter of intercellular spaces for individuals from the different populations across three experimental treatments of salinity. Our results demonstrate that high water salinity levels affected anatomical traits in all populations. However, the traits of freshwater populations were the more significantly impacted by increasing salinity compared with populations sampled from naturally higher occurring salinity. Populations of U. arrecta established in places with certain degree of salinity can be more resistance to salt increases compared with populations established in freshwater habitats that are more distant geographically. However, the resistance of freshwater populations to certain high salinity levels suggests that these populations may exhibit rapid adaptation and to survive under some degree of salinity, demonstrating the species' high resilience across various environments.