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Background: We studied the occurrence of two sympatric wallabies, the red-necked pademelon (Thylogale thetis) and the red-legged pademelon (T. stigmatica) in northeastern New South Wales, Australia in relation to structural habitat attributes. At our study site, both species inhabit closed forest environments and have overlapping distributions, but T. thetis leaves the forest at night to graze adjacent grassy forest edges whereas T. stigmatica remains within the forest and browses forest vegetation. The objectives of the study were to investigate how structural attributes of two forest types, wet sclerophyll forest and rainforest, relate to the fine-scale occurrence of these two wallaby species within the forested environment. Methods: We gathered occurrence data from 48 camera trap stations divided equally between rainforest and wet sclerophyll forest. At each camera point, we also measured a range of structural habitat attributes to determine habitat affiliations for the two Thylogale species. Principal component analyses were used to describe major trends in habitat, and generalised linear models were used to describe the efficacy of the variables in predicting habitat occurrence of each species. Results: The number of occurrences of Thylogale thetis was significantly greater than occurrences of T. stigmatica, which was driven by significantly greater occurrences of T. thetis in wet sclerophyll forest. There was both spatial and temporal partitioning between the two species; there was a significant difference in the occurrences of the two species at individual cameras and T. stigmatica had a different activity schedule than T. thetis in wet sclerophyll forest, where the latter reached its greatest rate of occurrence. At a finer (camera station) scale, occurrences of T. thetis increased with proximity to roads and grassy edges and at sites that were less rocky and less steep. T. stigmatica occurrence increased in the presence of rainforest elements like vines, palms and ferns, more ground-level cover and tree-fall gaps and at sites with fewer emergent eucalypts. Conclusion: Our findings have implications for managing these pademelons and their habitats. T. thetis is a common species that was encountered more often than T. stigmatica, and it responded positively to human disturbance like roadsides and grassy edges, presumably because these areas provided good grazing opportunities. By comparison, T. stigmatica is a threatened species, and it responded to natural disturbance like tree-fall gaps where lateral cover was greater, and where rainforest food plants may be more abundant. Our results suggest, therefore, that conservation of the threatened T. stigmatica requires the preservation of intact rainforest. [ABSTRACT FROM AUTHOR]

Understanding the physiological tolerances of ectotherms, such as thermal limits, is important in predicting biotic responses to climate change. However, it is even more important to examine these impacts alongside those from other landscape changes: such as the reduction of native vegetation cover, landscape fragmentation and changes in land use intensity (LUI). Here, we integrate the observed thermal limits of the dominant and ubiquitous meat ant Iridomyrmex purpureus across climate (aridity), land cover and land use gradients spanning 270 km in length and 840 m in altitude across northern New South Wales, Australia. Meat ants were chosen for study as they are ecosystem engineers and changes in their populations may result in a cascade of changes in the populations of other species. When we assessed critical thermal maximum temperatures (CTmax) of meat ants in relation to the environmental gradients we found little influence of climate (aridity) but that CTmax decreased as LUI increased. We found no overall correlation between CTmax and CTmin. We did however find that tolerance to warming was lower for ants sampled from more arid locations. Our findings suggest that as LUI and aridification increase, the physiological resilience of I. purpureus will decline. A reduction in physiological resilience may lead to a reduction in the ecosystem service provision that these populations provide throughout their distribution. [ABSTRACT FROM AUTHOR]

The study of environmental stress tolerance in aphids has primarily been at low temperatures. In these cases, and in the rare cases of high temperature tolerance assessments, all exposures had been during a single stress event. In the present study, we examined the physiological consequences of repeated high temperature exposure with recovery periods between these stress events in Myzus persicae. We subjected individuals to either a single prolonged three hour heating event, or three one hour heating events with a recovery time of 24 h between bouts. Aphids exposed to repeated bouts of high temperatures had more glucose and higher expression of proteins and osmolyte compounds, such as glycerol, compared to the prolonged exposure group. However, aphids exposed to the repeated high temperature treatment had reduced sources of energy such as trehalose and triglyceride compounds than the prolonged exposure group. Recovery time had more physiological costs (based on production of more protein and consumption of more trehalose and triglyceride) and benefits (based on production of more osmolytes) in repeated high temperature treatments. As aphids are known to respond differently to constant versus 'natural' fluctuating temperature regimes, conclusions drawn from constant temperature data sets may be problematic. We suggest future experiments assessing insect responses to thermal stress incorporate a repeated stress and recovery pattern into their methodologies.