Austral Ecology最新文献

Sampling of environmental DNA (eDNA) and high-throughput sequencing is emerging as an effective biodiversity assessment method in aquatic systems and may have utility for biodiversity inventory in terrestrial environments. Rock pools (gnammas) on granite inselbergs support a rich community of aquatic organisms and are culturally important to Indigenous peoples worldwide. However, the application of eDNA to survey rock pool biodiversity are undocumented. In a collaborative study with traditional owners, we explore the application of eDNA metabarcoding and traditional sampling methods to document and compare species richness and composition of eukaryotes from 15 rock pools (pits and pans) on granite inselbergs in southeastern Australia. We detected 116 taxonomic units, 81 assignments from eDNA sequencing and 35 species (23 rotifers and 12 microcrustaceans) using microscopic analysis. eDNA detected a broad range of taxa not previously documented from rock pools in Australia, although significantly more zooplankton (rotifers and microcrustaceans) were detected under a microscope, including several rare species and two undescribed species of rotifer. Brachionus calyciflorus and B. angularis were the only rotifer species assigned to species level through eDNA sequencing and were detected using both methods. We found no significant difference in mean species richness between rock pool types; however, species composition differed significantly between pits and pans. This study highlights the value of using eDNA to document biodiversity of ephemeral aquatic habitats in terrestrial ecosystems but reveals the general lack of reference sequence data for microorganisms, underscoring the value of using traditional sampling and taxonomic assignment methods.

Dietary data are vital for understanding species' resource requirements and ecological roles and supporting conservation efforts. The Blue-headed Macaw, Primolius couloni, is a vulnerable and endemic species in the Amazon. Due to their rarity, elusive nature, complex forest canopy habitat, and occurrence in remote areas, we minimally know their dietary habits. To address this gap, we analysed photographs of Blue-headed Macaws posted on wildlife-focused social media platforms, specifically targeting images that capture foraging behaviour on plants. Photographs depicting the same foraging were included only once, and those where the plants were not identified were discarded. By doing so, we identified 36 distinct foraging events (or photos), primarily taken between July and October, concentrated in specific locations in Peru and Brazil, a potential seasonality in foraging. We documented 27 food plant species and items such as nectar (n = 9 photos), pulp (8), seeds (7), buds, bark (5 each), aril, and leaves (n = 1 photo each). Notably, floral resources, including nectar, are a potentially important food in the driest months. Using Levin's Index (Ba), we identified a broad dietary niche, indicating a generalist feeding strategy with a wide variety of plant species (Ba = 0.69) and food items (Ba = 0.88). Additionally, the study revealed interactions such as florivory, seed predation, bark consumption, and potential mutualistic roles like pollination and seed dispersal. Our photo-centric approach here expanded the known dietary spectrum of the Blue-headed Macaw from four to 31 plant species, offering new insights for conservation strategies. We recommend the preservation of identified food plants and suggest using these data to inform habitat restoration efforts that support the macaws' dietary needs and ecological functions. Future research should focus on continuous monitoring of these food plants to deepen our understanding of seasonal foraging trends and ecological interactions and refine conservation approaches.

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.