Austral Ecology最新文献

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.

The Carajás region is home to the largest number of iron caves in Brazil, but studies that integrate elements of biological diversity and landscape characteristics are scarce. We present the first study based on the bat cave vulnerability index (BCVI), which uses bats as a key species for prioritizing caves in South America, whose objective was to assess the biotic potential and vulnerability of caves in the Carajás region, determining priority sites and the most effective conservation actions. The study took place from August 2021 to March 2023, where an inventory of the chiropterofauna of 12 caves was carried out. We recorded 16 bat species, two of which are vulnerable to extinction – Furipterus horrens (Cuvier, 1828) and Natalus macrourus (Gervais, 1856) – and two endemics to the Amazon region – Hsunycteris aff. thomasi (Allen, 1904) and Phyllostomus latifolius (Thomas, 1901); as well as one species with insufficient data to delimit its endemicity or threat status (Lonchophyllinae sp.). Mining is the main anthropogenic activity in the region, but tourism is also present and acts as a potential source of disturbance to the caves. The BCVI revealed three high priority caves for conservation and four with medium priority, indicating that these habitats are vulnerable to species loss and population decline due to exposure to anthropogenic activities and habitat destruction, thus requiring more effective conservation strategies. Considering the uniqueness of the subterranean habitats, we recommend re-evaluating the proposals for expanding mining activities, implementing controlled tourist visitation plans and conducting ecological studies and long-term monitoring.

Threatened species in rainforests may be vulnerable to climate change, because of their potentially narrow thermal tolerances, small population sizes, restricted distributions and limited dispersal. We investigated the relative influence of potential climate change on the population viability of Triunia robusta (Proteaceae), an endangered rainforest shrub endemic to southeast Queensland, Australia. A spatially explicit, stochastic population model with seven stage classes was developed and linked with the species distribution model (SDM) to explore a variety of hypothetical climate change simulations over a 90-year period from 2010 to 2100: (1) constant population dynamics, (2) changes in habitat distributions as trend in carrying capacity and (3) changes in habitat distributions, precipitation and temperature regime as relative change in seedling survival and fecundity. The results revealed high vulnerability of small populations to local extinction regardless of geographical location or climatic stressors, while some larger populations located in the southern end of the species distribution range showed persistence in-situ. Triunia robusta was found to be sensitive to reduced precipitation and increased temperature, limiting the species reproductive activities and seedling establishment and reducing the overall abundance consequently. Integration of population models and SDM allowed for the evaluation of multiple climatic stressors that may affect habitat distributions and population dynamics of T. robusta and ultimately suggest potential implications for future conservation and management planning with respect to climate change.

Termites are key components of tropical ecosystems, particularly in the Cerrado biome, where they dominate animal biomass and play crucial roles in nutrient cycling and soil formation. Their abundance and nutritional value make them primary food sources for various Cerrado animals, influencing predator diversity and several ecological interactions. Additionally, termite mounds serve as essential shelters for a wide range of fauna, aiding in thermoregulation and providing refuge from harsh environmental conditions, including wildfires. In this scenario, termitaria survival, diversity, and availability have several effects on the Cerrado fauna ecology. We present novel insights into the interaction between Actinobolus beetles and epigeous termite mounds in the Cerrado. Our field observations revealed Actinobolus beetles utilizing termite mounds for feeding and reproduction in several localities of Cerrado. These beetles access the inner portion of the termitaria, where the colony nest is located and protected by the termitaria's harder external layer and their larvae consume the termite nest structure. Actinobolus attack leads to partial or complete destruction of the colony and the creation of large hollows inside the mounds, causing deep changes in its structure. Despite the defensive mechanisms of termites, Actinobolus larvae thrive within the nest and likely ingest termites’ eggs, nymphae and adults. Furthermore, we found that the Actinobolus capsule are made of faecal pellets, instead of termitaria debris. We suggest that the interaction between Actinobolus beetles and epigeous termitaria impacts the role of termitaria in providing microclimate regulation, food and shelter for Cerrado fauna, likely having poorly understood effects on the conservation and management of Cerrado ecosystems.