Austral Ecology最新文献

Despite being a central aspect of a species' ecology and having important conservation implications, the use of fine-scale habitat features (microhabitats), and how they vary over time, are poorly known for most species. In this study, we leveraged 522 relocations of radio-tracked mallee tree dragons (Amphibolurus norrisi) and painted dragons (Ctenophorus pictus) to investigate the effect of environmental and individual variables on microhabitat use. Mallee tree dragons were more likely to use trees on hot days and in the middle of the day (the hottest time of day), whereas shrub use was more likely on cool days and in the mornings. Painted dragons were more likely to use shrubs and grass trees on warmer days and during the middle of the day, whereas burrows were used during cooler days and in the mornings and afternoons. We expect these patterns represent animals moving from refuge resources, occupied during unsuitable thermal conditions, to microhabitats offering basking, foraging and social opportunities during periods of thermal optimum. Additionally, we found evidence of an ontogenetic shift, with larger mallee tree dragons favouring tree use and higher perches, suggesting a transition from shrub to tree use with age. Our findings underscore the need for diverse microhabitats to accommodate the thermoregulatory and ontogenetic requirements of lizards. These insights can inform conservation and habitat restoration efforts, ensuring the provision of essential microhabitats to support species persistence.

Landscape productivity and resource dispersion are key drivers of the movement patterns of many species. In less productive environments, home ranges are generally larger as individuals travel further to access resources. The greater bilby (Macrotis lagotis) has been reintroduced to several feral predator exclosures to reduce their extinction risk. Understanding how landscape productivity and resource dispersion influence bilby space use is critical to enable effective management of populations in exclosures. At two exclosures, we tested three hypotheses: 1. Bilbies would preferentially utilize habitats with sandy substrates (<20% clay content), as they are suitable for digging burrows and foraging pits; 2. Home ranges would be larger at the arid site compared to the semi-arid site due to lower productivity and patchier distribution of preferred habitats; and 3. Bilbies would travel further each night at the arid site to access preferred habitats. Rainfall was used as an indicator of productivity, and dispersion of preferred habitats as an indicator of resource dispersion. The study was undertaken during average rainfall conditions and under similar bilby population densities at both sites. GPS loggers recorded home ranges and movements of 10 bilbies at the arid site, and 11 bilbies at the semi-arid site. Seventeen of the 21 bilbies preferentially utilized habitats with sandy substrates, which were less abundant at the arid site. There were no significant differences in home range size or nightly movements between the sites for either sex. We suggest the average rainfall conditions at both sites, and the dietary flexibility of bilbies, supported the maintenance of relatively small and stable home ranges (particularly for females). The effects of landscape productivity and resource dispersion on bilby space use are more likely to be evident during extended periods of below average rainfall. Bilby home range studies during low rainfall conditions (e.g. drought) are required for the effective, long-term management of exclosure populations.

Habitat loss is causing declines in native bees and reducing pollination services. Revegetation can be used to reverse these declines, and this restoration technique attracts growing efforts and resources. However, how the quality of revegetation affects native bee abundance, diversity and their pollination services is not well understood, and this limits opportunities to improve revegetation outcomes. To assess this gap, we surveyed floral and bee diversity in revegetated landscapes ranging in habitat quality, and compared these among each other and to remnant habitat and cleared areas. We also measured pollination services using two native phytometer species, which can be pollinated by native bees only, or by both native and introduced honey bees (Apis mellifera). We found that bee diversity and richness were higher within treatments that were higher in floral diversity. In addition, while pollination services provided by honey bees were uniform across treatments, remnant vegetation supported greater pollination services to the plant species pollinated by native bees only. These results indicate that higher quality revegetation characterized by the establishment of a more diverse set of plant species, has the potential to restore native bee diversity and associated pollination services. However, for the plant species investigated, restoration of pollination services had not occurred and might require more time. These results suggest preserving remnant vegetation should be the highest priority conservation action, and that restoration practitioners and landowners wishing to support landscape-level bee diversity and pollination services, should aim for revegetation using high flowering plant diversity.

Surface water drying challenges the persistence of lotic biological assemblages in non-perennial streams and rivers. However, the effects of natural hydrological disturbances on an assemblage depend on individual species characteristics. In this study, we investigated the structure and association of fish and macroinvertebrate assemblages during two phases in non-perennial streams (flowing vs. disconnected pools). We sampled fish and macroinvertebrate assemblages in five non-perennial stream reaches located in the Caatinga (Brazilian semi-arid region). Fish species were resistant to hydrological dynamics in the streams. On the other hand, some macroinvertebrate taxa from the flowing phase disappeared, and new taxa colonized the disconnected pools. The absence of lotic insects following flow cessation and the colonization of disconnected pools by lentic taxa facilitated macroinvertebrate assemblages persistence in these dynamic streams. Our study showed that fish and macroinvertebrate assemblages respond differently to the same natural flow cessation, which leads us to predict that flow changes will yield different assemblages, depending on the taxa. Thus, it is crucial to consider multi-assemblage responses to effectively manage and conserve non-perennial stream ecosystems in a tropical semi-arid region.

Cleistogamy is characterized by the presence of flowers that are permanently closed, yet they still produce fruits and seeds through autonomous self-pollination. Populations with cleistogamous flowers can also have flowers that open, called chasmogamous, which promote cross-pollination and genetic variability. Acanthaceae is among the families with the highest frequency of cleistogamy, observed mainly in Ruellia. This study aimed to assess cleistogamy in Ruellia blechum for the first time. In a population in Central Brazil, we analysed the production of cleistogamous and chasmogamous flowers, their fruiting, differences in flower bud size, self-pollination in cleistogamous flowers and visitors in chasmogamous flowers. Of the flower buds observed, 35.29% remained closed (cleistogamous flowers), with 31.25% of them forming fruit. In contrast, 60.24% of the flowers that opened (chasmogamous) developed fruit. The length of cleistogamous flowers was shorter than that of chasmogamous floral buds in pre-anthesis. On average, 24.45 pollen grains were self-deposited on the stigma of a cleistogamous flower. The chasmogamous flowers were visited mainly by small bees. This study is the first to confirm the presence of cleistogamous flowers in R. blechum. However, their co-occurrence with chasmogamous flowers suggests a fitness advantage for maintaining a mixed mating strategy.

Niche partitioning is a common strategy species use to avoid competition for limited resources, allowing them to coexist. Rodent species often reduce competition by spatial segregation and trophic differentiation, but behavioural differences, particularly related to foraging, can also be important. Therefore, temporal segregation can also be an important mechanism for species coexistence, as it helps them avoid sub-optimal habitats. We found three rodent species (the native Octodon degus and O. lunatus, and the exotic Rattus rattus) foraging on endemic palm Jubaea chilensis seeds, a highly valuable but limited resource. We hypothesized that these rodent species could coexist by segregating foraging in time, showing behavioural differences. To test this, we used camera traps to monitor the fate of J. chilensis seeds and rodent activity at 25 feeding stations. From 596 photographic records, we identified 128 as O. degus, 232 as O. lunatus and 236 as R. rattus. Octodon degus had a diurnal activity, while O. lunatus and R. rattus were nocturnal, showing significant temporal segregation. However, we found no spatial association among these rodents. We found significant behavioural differences in decision and handling times and seed removal rates, with O. degus having the greatest seed removal rate. Nevertheless, we found some nocturnal O. degus records in which the three rodent species were co-foraging, which may suggest that the resource is limited but valuable enough to shift from exploitation to interference competition. Our results suggest that temporal and behavioural differentiation are more important than spatial segregation and trophic differentiation. Thus, niche partition over multiple dimensions might allow for species coexistence.

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.