Austral Ecology最新文献

Plant species phenology is an important driver of invasions in seasonal climates. The phenology of non-natives is generally uncoupled from that of native species. Grasses cover a large proportion of the land surface and are important invaders around the world. Interestingly, the phenology of native and non-native grasses could be modulated by the different metabolic pathways. We aimed to compare the vegetative and reproductive phenology of invasive C₄ grasses with that of coexisting native C₃ and C₄ grasses and to explore the relationship between phenology and climate. We recorded the onset, duration and synchronicity of vegetative and reproductive phenology (flowering and fruiting) during 1 year. Native C₃ grasses had 50% of their above-ground biomass green earlier and remained in that state for a longer period than non-native and native C₄ grasses. Flowering and fruiting occurred earlier in non-native C₄ grasses than in native C₄ grasses. The flowering period was longer in non-native C₄ than in native C₃ and C₄, with the non-native Melinis repens (Poaceae), a highly invasive species worldwide, accounting for most of the difference. Non-native C₄ tended to exhibit a lower flowering and fruiting synchrony than both native C₃ and C₄ species. Finally, reproductive and vegetative phenology was positively associated with temperature, while precipitation was mostly associated with C₄ species. The uncoupled vegetative phenology observed could be related to differences in metabolism among the studied species, while the uncoupled reproduction between non-native and native C₄ grasses could be due to an advantage in resource use by non-native species. Our work provides the first insight into the possible role of the species origin and metabolic pathways in the vegetative and reproductive phenology of invasive non-native C₄ and native C₃ and C₄ grasses. Finally, we suggest future directions to elucidate these processes.

Since the late 1800s, north Australian savannas have experienced a fundamental shift in grazing pressure, moving from an assemblage of native macropods to introduced ungulates. In contrast to macropods, ungulates have hard hooves, are greater in size and exhibit bulk feeding strategies, resulting in a greater impact on perennial grass cover. However, the response of perennial grasses to ungulate grazing may vary depending on rainfall, soil fertility and fire, as well as ungulate density and feeding behaviour. Interactions between grazing, drought and fire are of particular interest, as climate change is predicted to increase rainfall variability and fire frequency across northern Australia. In this study, we tested for interactions between grazing and drought, as well as fire and grazing, on two vegetation zones surrounding waterholes, through a 5 years fencing exclusion experiment. Despite drought conditions occurring over 2 years of the study, no interaction between grazing and drought was detected. This is most likely due to the relatively low ungulate density present during the study (~1 ungulate/km²). In contrast, after fire was introduced to the study sites, significantly more perennial grass cover was recorded at fenced sites relative to unfenced sites. Due to the study design the cause of change cannot be directly inferred. However, when the potential drivers are considered further (rainfall, soil properties, fire and changes in ungulate density), an interaction between grazing and fire is the most probable cause. Wetland vegetation showed a stronger response to fencing than the surrounding savanna, with this result most likely due to differences in ungulate feeding behaviour between the two vegetation zones. Our findings are important, as fire and ungulate grazing are both widespread across Australia's savannas and reduced perennial grass cover has been linked to increased cat predation on rapidly declining small, native mammal populations.

Understanding the dietary components of a species can help reveal complex ecological interactions within an ecosystem. We analysed the diet of a native semi-aquatic predator, the rakali (Hydromys chrysogaster), to investigate its reported preference for invasive species in a regulated freshwater system. We used faecal metabarcoding analysis to identify key dietary items consumed during winter in the Yanco Creek System of southern New South Wales. While rakali did not display a significant difference in the consumption of invasive and native fish, 79.5% of total fish relative read abundance were invasive. The common carp (Cyprinus carpio) comprised 16.8% of the total diet relative read abundance and was present in 78.6% of samples. Plant matter was present in all samples and over half of the total relative read abundance of the diet. The prevalence of plants in the winter diet of rakali indicates that they are an important dietary supplement when other resources are limited. We show that the prevalence of invasive fish consumed by rakali is likely a result of their greater abundance in the system, rather than a direct preference. Further research is needed to determine the extent to which rakali can control invasive prey populations.

Animal gut microbiomes can be very diverse, and enteric bacteria can profoundly affect the physiology of their host. The gut microbiome can be related to host health and digestion, which ultimately contribute to host body condition. However, we have a limited understanding of the co-occurrence patterns of gut bacteria in their host, and how co-occurrence and bacterial diversity change over time. This notion is especially important to animals living in groups as bacteria can transmit through social interactions. We investigated the co-occurrence patterns of gut bacteria in a lizard host. We repeatedly collected cloacal swabs from 87 sleepy lizards (Tiliqua rugosa) from two different study sites over their activity season. We determined the richness and prevalence of 82 enteric bacterial strains and used a probabilistic model to investigate their co-occurrence. At both study sites, richness and prevalence generally increased over time. We suggest that the lizards acquire strains throughout their activity season by moving through the landscape and inspecting conspecific scats. Lizards continuously tongue-flick while moving, and thereby ingest bacteria when they move through areas where other animals defaecated. Temperature, rainfall and diet change seasonally, influencing lizard activity, and may influence the observed increase in enterobacterial richness and prevalence. Further, albeit with some exceptions, most strain pairs did not occur significantly more often or less often than expected by chance. This finding shows a lack of structured co-occurrence, which may imply that most bacterial strains did not facilitate or inhibit each other. The absence of a co-occurrence pattern could also be driven by random encounters of bacteria shed by other lizards within the habitat. Our results suggest that behaviour (movement patterns, tongue-flicking), activity patterns and environmental factors collectively drive the temporal pattern of the gut bacterial community in sleepy lizards and potentially other wild reptiles.

In the current study, I report a single-site mimicry complex involving 20 arthropods from 12 families in five orders resembling the small turtle ant Cephalotes pusillus. The complex is the most species-rich single-site complex with predominately Batesian mimics that has been reported so far. Considering that small turtle ants are likely less defended than highly noxious butterflies or aculeate Hymenoptera with potent stingers, possible factors explaining the high species richness of the complex may include high model abundance, small body size and easy to develop morphological resemblance.

Altitudinal gradients can provide valuable insights into the distribution patterns of species richness at both local and regional scales. Typically, species richness peaks at intermediate elevations. This pattern can be attributed to factors such as climatic conditions, the mid-domain effect, and historical-evolutionary processes. Our research aimed to investigate the distribution patterns of vascular epiphytes along the regional elevation gradient in dwarf cloud forests of Serra da Mantiqueira (SM), Brazil. We hypothesised that species richness would peak at intermediate elevations correlating with the availability of water. To test this hypothesis, we sampled 18 plots, each measuring 20 × 20 m, in seven protected areas with varying elevation gradients. The lowest plot was at 1270 m, and the highest was at 2350 m. In each plot, we surveyed trees (phorophytes) with a circumference at breast height of 30 cm. Rarefaction analysis was conducted to compare species richness among plots, while beta diversity analysis was used to assess species composition changes along the elevation gradient and across the SM range. We employed a generalised linear model (GLM) with a Poisson distribution to examine the relationships between environmental variables and plant richness. Our findings suggest that there is no intermediate peak in species richness in any of the localities. However, regionally, the elevation range of 1500-1700 m exhibited the highest richness, particularly when compared to the higher plots, which are subject to low temperatures that act as environmental filters, limiting species richness despite higher precipitation. Furthermore, plots above 1980 m showed low turnover, indicating that these filters contribute to a more homogeneous composition. Species composition across the SM was influenced by climatic differences, and overall, geographical distance was not significant, as within the same locality exhibited low turnover. This study provides a foundation for understanding patterns of species richness and composition along altitudinal gradients in the context of global climate change.

An understanding of fine-scale movements made by animals is critical for assessing localized habitat preferences and informing the scales over which land management should be applied. However, for cryptic species such as insectivorous bats that are highly mobile and active at night, it is difficult to collect these data. Nyctophilus corbeni serves as a case study for narrow-space species as it is listed as threatened and nothing is known about its localized habitat preferences. We used miniature GPS tags to assess fine-scale movements across three sites and 2 years (autumn 2020 and 2021) in the Pilliga forests in northwest New South Wales. Each site consisted of a mosaic of forest disturbances (e.g. timber harvesting / thinning regrowth, prescribed fires and wildfires, and cleared farmland). Bats made large movements in the non-maternity season, with a maximum of ~21 km recorded as a one-way movement on a given night. On average, the maximum distance travelled by tagged bats was 6.2 ± 1.4 km per night. Short-term home (9884 ha) and core (2157 ha) ranges were extensive, but varied by sex, with ranges of females ~15 times larger than males. Bats crossed cleared land that was within close proximity (<2.3 km, but typically <~600 m) of large forest blocks (>100 ha). Based on availability of habitat types, bats selected for older regrowth and burnt forest and avoided cleared areas with scattered trees and also thinned forest, though the availability for the latter was low (<3 %). Flight speeds and the lack of clustering of GPS fixes in cleared landscapes suggest that limited foraging may occur there. Overall, our results highlight the sensitivity of the species to forest clearing and potentially to thinning, but also demonstrate the importance of maintaining large areas of forest and where possible, reforesting cleared areas that occur between smaller, more isolated forest blocks.

Understanding species distribution patterns has been a major quest in biodiversity research. Due to their secretive habits and rarity, snakes have been historically underrepresented in assessments of geographic distribution range. In this work, we employ a pipeline for predictive model-based species sampling, using Neotropical snakes as a model organism. We employ species distribution models based on verified point records for five candidate snake species of probable occurrence to Rio Grande do Sul state, Brazil: Apostolepis dimidiata (Jan 1862), Erythrolamprus aesculapii (Linnaeus 1758), Helicops leopardinus (Schlegel 1837), Lygophis meridionalis (Schenkel 1901), and Micrurus corallinus (Merrem 1820). Based on the resulting models, we conducted fieldwork on areas with higher overlap of suitable ranges and probability of new records. Our study yields a new state record of A. dimidiata to Rio Grande do Sul and highlights the usefulness of species distribution models in eliciting priority areas for faunal assessments.

Frugivorous bats in the subfamily Stenodermatinae are known to use foliage and cavities, such as tree hollows or caves, as roosting sites. Species with paler facial and dorsal markings are typically thought to prefer enclosed spaces, while those with more conspicuous markings often roost in more exposed locations. Among the genus Chiroderma, the hairy big-eyed bat (C. villosum) has the widest distribution and is the most studied ecologically, yet its roosting habits remain poorly understood. We present three observations of C. villosum using foliage as daytime roosting sites, with records from tropical rainforest areas in Belize, Brazil and Nicaragua. These findings challenge the assumption that C. villosum prefers enclosed spaces due to its less conspicuous pelage markings. The apparent scarcity of day roost reports for Chiroderma species may be due to their solitary roosting habits and the difficulty of spotting them in exposed shelters.

The threatened South-eastern Long-eared Bat (Nyctophilus corbeni, EPBC Act 1999 Vulnerable) is an insectivorous microbat that is dependent on tree hollows for roosting. Although it is sparsely distributed throughout the Murray-Darling Basin, its contemporary Victorian distribution was believed to be limited to a small population in semi-arid mallee habitats in the state's North-West. That was until a lactating female was captured in the floodplain forest in Gunbower National Park, along the Murray River in north-central Victoria, in late 2021. In light of this new record, in an ecological setting not typically occupied by the species, we sought to (a) confirm the presence of an established population of N. corbeni at Gunbower; and (b) if present, characterize the day roosts being used. Over eight nights (73 trapnights), we captured 172 microbats, including five N. corbeni. Traps set with acoustic lures (the Autobat MK2, or a generic bat chirper) appeared to capture more bats per trapnight than those set without lures. Four individual N. corbeni were successfully radiotracked to their roosts, which were a mix of small-diameter (19.5–36 cm DBH), typically multi-stemmed, live, dying and dead Black Box (Eucalyptus largiflorens) and Grey Box (Eucalyptus microcarpa) trees. While day roosts do not appear to be limiting for this species in this location, further research is needed to understand what trees are being used as maternity roosts (which may be more specialized), how far up- and down-stream along the Murray River this new population extends, and whether it is geographically and/or genetically connected to populations in the Victorian mallee or in New South Wales.