Austral Ecology最新文献

Describing and quantifying the foraging ecology of wildlife is important for fundamental ecological theory and understanding the roles species play within ecosystems. Further, such information can be applied to help guide conservation actions, such as predictions of ecological outcomes resulting from threatened species translocations aimed at reestablishing self-sustaining populations and restoring functions to ecosystems. Our study investigated the diet of two populations of Eastern Barred Bandicoots (Perameles gunnii, mainland populations) introduced to fox-free islands (Churchill Island and Phillip Island, southeastern Australia) outside of the species' historical range. Microscopic analysis of faeces revealed that bandicoots exhibit an omnivorous diet, consuming a broad range of invertebrate, plant and fungal material, similar to previous studies of their diet within their natural range. Commonly identified invertebrate taxa included earthworms, beetle adults and larvae, ants, cockroaches, spiders and caterpillars. Notably, crabs were also found in bandicoot diet, indicating the species' ability to adapt to and use coastal (novel) environments. Seasonality was the main factor associated with changes in bandicoot diet at Churchill Island, suggesting that the species is a facultative generalist omnivore that shifts feeding seasonally, likely in relation to variation in food availability. Diet also shifted in response to bandicoot density, likely related to the expansion of the bandicoot population into more diverse habitats across the island. The inherent flexibility of Eastern Barred Bandicoot diet means they are well-suited for additional conservation translocations although prior assessments of recipient ecosystems are needed.

Understanding early ontogenetic transitions in fish is essential for reconstructing life histories and to refine age and growth assessments. In this study, we combined microchemical and crystallographic analyses of sagittal otoliths to investigate early developmental stages in Micropogonias furnieri, a key estuarine species in the Southwestern Atlantic. Raman spectroscopy revealed that otoliths remain crystallographically stable throughout early development, with aragonite as the sole calcium carbonate polymorph even in regions of structural reorganisation. Core-to-edge Sr/Ca, Ba/Ca and Mn/Ca profiles were analysed by LA-ICP-MS on sagittal otoliths sectioned to expose the core. Elemental profiles exhibited trends aligned with key physiological and environmental transitions: a high Sr/Ca signal in the core (pre-hatch and larval stage) in most samples, a Mn/Ca peak during metamorphosis and a progressive increase in Ba/Ca spanning the metamorphic and juvenile stages. Interindividual variability and partial misalignment with microstructural markers were observed, likely due to the complexity of the region of the otolith formed during metamorphosis and probably due to environmental heterogeneity in the Río de la Plata Estuary. These findings suggest that combining otolith elemental ratios may serve as biological “timers” to retrospectively identify early life stages, enhancing age and growth studies in estuarine fish with complex life cycles.

Intra- and interspecific interactions may structure complex competitive scenarios in which the arrival time at a resource may play a key role in determining how individuals and populations are maintained. The speed and efficiency by which the dung beetles locate and colonise dung pads, which comprise an ephemeral and randomly distributed resource, may vary according to their physiological condition, sex, and body temperature. This study aimed to analyse how the sex, morphological traits, physiological conditions, and body temperature of dung beetles determine the time each individual spends reaching food resources. We performed field observations in arenas, recording the time spent by Phanaeus pseudofurcosus Bathasar, 1939, and Phanaeus obliquans Bates, 1887 individuals to reach the food resource. Dung beetles with lower temperatures arrived more rapidly at the dung pad. The body temperature of female dung beetles was the only variable explaining arrival time at the dung pad, with warmer females of both species arriving later. Males of P. pseudofurcosus with more muscle mass arrived later at the dung pad than those with lower muscle mass. The body temperature of P. obliquans individuals arriving at the dung pad depended on the environmental temperature. In summary, the arrival of dung beetles at food resources is influenced by physiological condition and temperature, and is also a species and sex-dependent dynamic. This pattern of arrival time appears to be determined by a complex set of species-specific conditions, with each species responding to distinct physiological and thermal dynamics.

Understanding how invasive species adjust to temperature variation is critical to predicting their responses to climate change. We tested for population-level adjustment in germination responses of the invasive species Hieracium pilosella L. (Asteraceae, syn. Pilosella officinarum Vaill.) along a 120-km climatic gradient in Tierra del Fuego Island, Argentina. We collected seeds from six populations varying in mean growing season temperature and exposed them to five constant temperatures (5°C, 10°C, 15°C, 20°C, and 25°C) in growth chambers. We analysed the interaction between population temperature (PT) and chamber temperature (CT) as a test of local adjustment, hypothesizing that populations from warmer sites would germinate best at warmer experimental temperatures. Germination percentage, our focal demographic rate, was strongly influenced by a positive PT × CT interaction (standardised coefficient = 0.27), supporting the hypothesis of local adjustment. This clinal pattern likely reflects a combination of mechanisms, with rapid local adaptation and maternal environmental effects being the most plausible contributors. Notably, our observed germination rates (up to 80%) greatly exceeded those reported in earlier studies, possibly reflecting apomictic reproduction, ploidy variation, or hybrid origin in Fuegian populations. These traits may facilitate rapid germination responses and enhance invasion potential under warming scenarios. Given projected warming and drying in the region, H. pilosella is likely to benefit from climate change, especially if native species cannot match its rapid germination adjustment. More broadly, our analytical approach yields a continuous measure of population adjustment strength that is easily comparable across gradients and species, unlike traditional analyses based on the population-identity × CT interaction. Quantifying interactions between field collection conditions and experimental environments offers a valuable framework to assess environmental adjustment and potential evolutionary responses in invasive species.

Pre-industrial forests are largely absent from environments long modified by humans, such as the Mediterranean region of central Chile. Around the capital, Santiago (33° S), the dominant vegetation is the “matorral,” characterised by shrubs, small trees, and succulents. However, colonial records indicate the presence of forests in this area. Here, we document for the first time the age, composition, and diameter distribution of a small remnant patch of primeval forest within the Río Clarillo National Park (RCNP), 45 km from Santiago. In this patch and in five surrounding matorral areas, we established 50 × 20 m plots, where we measured all trees with the diameter at breast height (DBH) > 5 cm. In the forest plot, we aged 36 trees using increment borers. The DBH showed an inverted J-distribution, dominated by the shade-tolerant Cryptocarya alba and Persea lingue (both Lauraceae) with individuals up to 1 m dbh and between 15 and 20 m tall. The basal area was 64 m²/ha, with 1140 trees/ha, and minimum ages ranged from 75 to 145 years. The matorral plots' trees were concentrated in smaller diameter classes (< 30 cm DBH), with an average basal area of 16.7 m² ± 6.5 m². The forest exhibited characteristics of late-successional stands and differed markedly from the surrounding matorral. The RCNP was first logged for charcoal in the mid-20th century, much more recently than many other areas of central Chile. The physiognomy of this patch resembles descriptions from 19th and early 20th century scholars. We hypothesise that forests like this were once much more common in the landscape than previously thought, and that present-day matorral represents an early successional forest maintained by recurrent human use. This patch represents a biological legacy from the past, provides a reference for long-term ecological restoration, and is unique, irreplaceable, and of immense value for conservation.

Large, severe wildfires are a major threat to biodiversity. Land managers often use prescribed fire to mitigate wildfire risks; however the impact of this strategy on many species remains poorly understood. We used a control-impact study to quantify the population response of the long-nosed potoroo (Potorous tridactylus) to prescribed fire. Live trapping was conducted at one unburnt control site and two burnt sites 12- and 24-months after small, patchy winter prescribed fires in a heathy woodland ecosystem, in south-eastern Australia. We estimated population density using spatially explicit capture-recapture analysis, and derived a relative abundance index which we compared to density using linear regression. At 12-months post-fire, estimated mean potoroo densities were 107 individuals per km² at the control site, 49 at Burn 1 and 119 at Burn 2. Compared to the control, densities were 54% lower at Burn 1 and 11% higher at Burn 2. At 24-months post-fire, densities were 176 potoroos per km² at the control, 76 at Burn 1 (57% lower than the control) and 137 at Burn 2 (22% lower than the control). There was no evidence that increases in density over time differed among sites. Despite substantial spatial and temporal variation in density, potoroos appeared resilient to patchy winter burns at these sites 2 years post-fire, although a fire-driven decline could not be ruled out due to the absence of pre-fire data. Density and relative abundance were positively correlated (R² = 0.90), and the relationship remained strong under a reduced sampling effort of at least four trap nights. These findings suggest that relative abundance may serve as a reliable proxy for potoroo density under certain conditions. This study improves our understanding of how a vulnerable Australian mammal responds to patchy winter burns, and shows that biodiversity conservation and fuel reduction may be compatible goals in some landscapes.