Simplification of arboreal marsupial assemblages in response to increasing urbanization

Arboreal marsupials play an essential role in ecosystem function including regulating insect and plant populations, facilitating pollen and seed dispersal and acting as a prey source for higher-order carnivores in Australian environments. Primarily, research has focused on their biology, ecology and response to disturbance in forested and urban environments. We used presence-only species distribution modelling to understand the relationship between occurrences of arboreal marsupials and eco-geographical variables, and to infer habitat suitability across an urban gradient. We used post-proportional analysis to determine whether increasing urbanization affected potential habitat for arboreal marsupials. The key eco-geographical variables that influenced disturbance intolerant species and those with moderate tolerance to disturbance were natural features such as tree cover and proximity to rivers and to riparian vegetation, whereas variables for disturbance tolerant species were anthropogenic-based (e.g., road density) but also included some natural characteristics such as proximity to riparian vegetation, elevation and tree cover. Arboreal marsupial diversity was subject to substantial change along the gradient, with potential habitat for disturbance-tolerant marsupials distributed across the complete gradient and potential habitat for less tolerant species being restricted to the natural portion of the gradient. This resulted in highly-urbanized environments being inhabited by a few generalist arboreal marsupial species. Increasing urbanization therefore leads to functional simplification of arboreal marsupial assemblages, thus impacting on the ecosystem services they provide.

Fish assemblages associated with oil industry structures on the continental shelf of north-western Australia

This study provides the first assessment of fish associations with oil and gas structures located in deep water (85-175 m) on Australia's north-west continental shelf, using rare oil industry video footage obtained from remotely operated vehicles. A diverse range of taxa were observed associating with the structures, including reef-dependent species and transient pelagic species. Ten commercially fished species were observed, the most abundant of which was Lutjanus argentimaculatus, with an estimated biomass for the two deepest structures (Goodwyn and Echo) of 109 kg.

Invasive carnivores alter ecological function and enhance complementarity in scavenger assemblages on ocean beaches

Species composition is expected to alter ecological function in assemblages if species traits differ strongly. Such effects are often large and persistent for nonnative carnivores invading islands. Alternatively, high similarity in traits within assemblages creates a degree of functional redundancy in ecosystems. Here we tested whether species turnover results in functional ecological equivalence or complementarity, and whether invasive carnivores on islands significantly alter such ecological function. The model system consisted of vertebrate scavengers (dominated by raptors) foraging on animal carcasses on ocean beaches on two Australian islands, one with and one without invasive red foxes (Vulpes vulpes). Partitioning of scavenging events among species, carcass removal rates, and detection speeds were quantified using camera traps baited with fish carcasses at the dune–beach interface. Complete segregation of temporal foraging niches between mammals (nocturnal) and birds (diurnal) reflects complementarity in carrion utilization. Conversely, functional redundancy exists within the bird guild where several species of raptors dominate carrion removal in a broadly similar way. As predicted, effects of red foxes were large. They substantially changed the nature and rate of the scavenging process in the system: (1) foxes consumed over half (55%) of all carrion available at night, compared with negligible mammalian foraging at night on the fox-free island, and (2) significant shifts in the composition of the scavenger assemblages consuming beach-cast carrion are the consequence of fox invasion at one island. Arguably, in the absence of other mammalian apex predators, the addition of red foxes creates a new dimension of functional complementarity in beach food webs. However, this functional complementarity added by foxes is neither benign nor neutral, as marine carrion subsidies to coastal red fox populations are likely to facilitate their persistence as exotic carnivores.

A bust but no boom: responses of floodplain bird assemblages during and after prolonged drought

Climate change alters the frequency and severity of extreme events, such as drought. Such events will be increasingly important in shaping communities as climate change intensifies. The ability of species to withstand extreme events (resistance) and to recover once adverse conditions abate (resilience) will determine their persistence. We estimated the resistance and resilience of bird species during and after a 13-year drought (the 'Big Dry') in floodplain forests in south-eastern Australia. We conducted bird surveys at the beginning and end of the Big Dry, and after the abrupt end to the drought (the 'Big Wet'), to evaluate species-specific changes in reporting rates among the three periods. We assessed changes in bird-breeding activity before and after the Big Wet to estimate demographic resilience based on breeding. Between the start and the end of the Big Dry (1998 vs. 2009), 37 of 67 species declined substantially. Of those, only two had increased reporting rates after the Big Wet (2009 vs. 2013) that were equal to or larger than their declines, while three partially recovered. All other declining species showed low resilience: 25 showed no change in reporting rates and seven declined further. The number of breeding species and total breeding activity of all species declined after the Big Wet, and there was no change in the number of young produced. The Big Dry caused widespread declines in the floodplain avifauna. Despite the drought being broken by 2 years of well-above-average rainfall and subsequent near-average rainfall, most species showed low resilience and there was little indication that overall breeding had increased. The effects of drought appeared to be pervasive for much of the floodplain avifauna, regardless of species traits (species body mass, fecundity, mobility or diet). Ecosystems such as these are likely to require active management and restoration, including reinstatement of natural flooding regimes, to improve ecological condition, to enhance resistance and resilience to extreme climate events.

Towards a "non-didactic didacticism" of the sociopolitical: assemblages and the event in surface tension and shame

To write sociopolitical fiction is to be caught in an odd double bind. The term itself, ‘sociopolitical’ (hyphenated or not), implies an ‘assemblage’, and the terms it combines—‘the social’ and ‘the political’—each suggest complex, worldly assemblages. However, the more the writer attempts to express the assembled complexity of the sociopolitical domain, the more he/she feels a tug in the other direction: towards the version of ideas that might best explain the sociopolitical world and motivate political action. This article engages with the aesthetic and political challenges that arise in writing within a genre in which, to some extent at least, a moral content is desired by readers as an explanation for sociopolitical issues, only to be resisted when, as it often does, it becomes didactic. Co-author Cathryn Perazzo’s sociopolitical novel-in-progress, Surface Tension, is, we suggest, a laboratory of an assemblage in action. In it, we test and elaborate our hypothesis of the ‘assembled idea’ or ‘assembled morality’ of the sociopolitical novel. We conclude with a look at a published short story, ‘Shameʼ, by co-author Patrick West, which similarly deals with the sociopolitical, with how ‘non-didactic didacticisms’ might be germinated, and, most explicitly, with the ‘event’, following Deleuze’s use of this term.

Avian assemblages at bird baths: a comparison of urban and rural bird baths in Australia

Private gardens provide habitat and resources for many birds living in human-dominated landscapes. While wild bird feeding is recognised as one of the most popular forms of human-wildlife interaction, almost nothing is known about the use of bird baths. This citizen science initiative explores avian assemblages at bird baths in private gardens in south-eastern Australia and how this differs with respect to levels of urbanisation and bioregion. Overall, 992 citizen scientists collected data over two, four-week survey periods during winter 2014 and summer 2015 (43% participated in both years). Avian assemblages at urban and rural bird baths differed between bioregions with aggressive nectar-eating species influenced the avian assemblages visiting urban bird baths in South Eastern Queensland, NSW North Coast and Sydney Basin while introduced birds contributed to differences in South Western Slopes, Southern Volcanic Plains and Victorian Midlands. Small honeyeaters and other small native birds occurred less often at urban bird baths compared to rural bird baths. Our results suggest that differences between urban versus rural areas, as well as bioregion, significantly influence the composition of avian assemblages visiting bird baths in private gardens. We also demonstrate that citizen science monitoring of fixed survey sites such as bird baths is a useful tool in understanding large-scale patterns in avian assemblages which requires a vast amount of data to be collected across broad areas.

Short-term differences in animal assemblages in patches formed by loss and growth of habitat

Ecological theory predicts that habitat growth and loss will have different effects on community structure, even if they produce patches of the same size. Despite this, studies on the effects of patchiness are often performed without prior knowledge of the processes responsible for the patchiness. We manipulated artificial seagrass habitat in temperate Australia to test whether fish and crustacean assemblages differed between habitats that formed via habitat loss and habitat growth. Habitat loss treatments (originally 16 m2) and habitat growth treatments (originally 0 m2) were manipulated over 1 week until each reached a final patch size of 4 m2. At this size, each was compared through time (0-14 days after manipulation) with control patches (4 m2 throughout the experiment). Assemblages differed significantly among treatments at 0 and 1 day after manipulation, with differences between growth and loss treatments contributing to most of the dissimilarity. Immediately after the final manipulation, total abundance in habitat loss treatments was 46% and 62% higher than controls and habitat growth treatments, respectively, which suggests that animals crowded into patches after habitat loss. In contrast to terrestrial systems, crowding effects were brief (≤1 day), signifying high connectivity in marine systems. Growth treatments were no different to controls, despite the lower probability of animals encountering patches during the growth phase. Our study shows that habitat growth and loss can cause short-term differences in animal abundance and assemblage structure, even if they produce patches of the same size.

Landscape properties mediate the homogenization of bird assemblages during climatic extremes

Extreme weather events, such as drought, have marked impacts on biotic communities. In many regions, a predicted increase in occurrence of such events will be imposed on landscapes already heavily modified by human land use. There is an urgency, therefore, to understand the way in which the effects of such events may be exacerbated, or moderated, by different patterns of landscape change. We used empirical data on woodlanddependent birds in southeast Australia, collected during and after a severe drought, to document temporal change in the composition of bird assemblages in 24 landscapes (each 100 km2) representing a gradient in the cover of native wooded vegetation (from 60% to <2%). We examined (a) whether drought caused region-wide homogenization of the composition of landscape bird assemblages, and (b) whether landscape properties influenced the way assemblages changed in response to drought. To quantify change, we used pairwise indices of assemblage dissimilarity, partitioned into components that represented change in the richness of assemblages and change in the identity of constituent species (turnover). There was widespread loss of woodland birds in response to drought, with only partial recovery following drought-breaking rains. Region-wide, the composition of landscape assemblages became more different over time, primarily caused by turnover-related differentiation. The response of bird assemblages to drought varied between landscapes and was strongly associated with landscape properties. The extent of wooded vegetation had the greatest influence on assemblage change: landscapes with more native vegetation had more stable bird assemblages over time. However, for the component processes of richness- and turnoverrelated compositional change, measures of landscape productivity had a stronger effect. For example, landscapes with more riparian vegetation maintained more stable assemblages in terms of richness. These results emphasize the importance of the total extent of native vegetation, both overall cover and that occurring in productive parts of the landscape, for maintaining bird communities whose composition is resistant to severe drought. While extreme climatic events cannot be prevented, their effects can be ameliorated by managing the pattern of native vegetation in anthropogenic landscapes, with associated benefits for maintaining ecological processes and human well-being.

The use of traits to interpret responses to large scale - edge effects: a study of epigaeic beetle assemblages across a Eucalyptus forest and pine plantation edge

Context: Edge effects due to habitat loss and fragmentation have pervasive impacts on many natural ecosystems worldwide. Objective: We aimed to explore whether, in tandem with the resource-based model of edge effects, species feeding-guild and flight-capacity can help explain species responses to an edge. Methods: We used a two-sided edge gradient that extended from 1000 m into native Eucalyptus forest to 316 m into an exotic pine plantation. We used generalised additive models to examine the continuous responses of beetle species, feeding-guild species richness and flight-capable group species richness to the edge gradient and environmental covariates. Results: Phytophagous species richness was directly related to variation in vegetation along the edge gradient. There were more flight-capable species in Eucalyptus forest and more flightless species in exotic pine plantation. Many individual species exhibited multiple-peaked edge-profiles. Conclusions: The resource based model for edge effects can be used in tandem with traits such as feeding-guild and flight-capacity to understand drivers of large scale edge responses. Some trait-groups can show generalisable responses that can be linked with drivers such as vegetation richness and habitat structure. Many trait-group responses, however, are less generalisable and not explained by easily measured habitat variables. Difficulties in linking traits with resources along the edge could be due to unmeasured variation and indirect effects. Some species’ responses reached the limits of the edge gradient demonstrating the need to examine edge effects at large scales, such as kilometres.