Persistence and survival of the spider <Emphasis Type="Italic">Nephila plumipes</Emphasis> in cities: do increased prey resources drive the success of an urban exploiter?

Species that successfully inhabit urban ecosystems are rare, and urbanisation often drives localised extinctions of native species. Nonetheless, some species take advantage of the novel conditions available in cities and increase in abundance. Trends in the abundance and distribution of species in urban areas have received much attention, but the precise elements of urban ecosystems that affect the survival of urban-dwelling species are largely unknown. Animals that successfully exploit urban environments may do so because of increases in the availability of resources or habitats. Here we assess the effects of anthropogenic landscapes and prey abundance on the persistence of an orb-weaving spider, Nephila plumipes. We assessed spider persistence for six months in situ along an urban gradient in Sydney. We then transplanted spiders from a common garden into sites along the gradient, monitored their persistence in the new environment and measured a suite of environmental variables at local and landscape scales. The abundance of prey was closely linked with spider persistence, in both the survey and the transplant experiment, and was positively associated with anthropogenic habitats. The surveyed spiders survived longer when located closer to the coast and transplanted spiders persisted longer in smaller sites with more impervious surfaces and reduced vegetation cover. Our study shows that urbanisation has a strong effect on potential prey abundance and can lead to increased persistence of N. plumipes, demonstrating the broad impacts that habitat disturbance can have on the life history and trophic interactions of city-dwelling animals.     

Urbanization affects the trophic structure of arboreal arthropod communities

Urbanization is one of the most significant causes of habitat fragmentation on the planet, resulting in substantial losses of biodiversity and disruptions to ecological processes. We examined the effects of urbanization on the diversity and abundance of arboreal invertebrates in a dominant tree species (Angophora costata) in a highly urbanized landscape in Sydney, Australia, identifying the potential ecological consequences of shifts in diversity. We hypothesized that trophic structure would be influenced by landscape context with a greater richness and abundance of invertebrates in small remnants and edges. Canopy arthropods were sampled via beating from trees in 15 sites in three landscape contexts; five large patches of continuous vegetation, five edges of large patches and five small urban remnants. Trees in large patches supported fewer individuals compared to trees in small urban remnants and edge sites. The composition of assemblages and overall trophic structure also differed between edges and large patches, with a greater abundance of grazing insects in edges. No differences were detected between small urban remnants and edges, suggesting that observed differences might be attributed to an edge effect as opposed to an area effect per se. These changes in trophic structure, revealing a greater abundance of grazing herbivores and a reduced abundance of predators and parasitoids in edge sites, are consistent with work describing elevated levels of herbivory in edges of remnant vegetation. Future management of remnant urban vegetation and associated biodiversity requires not only an understanding of how trophic status influences the extent of responses by arboreal invertebrate communities, but also how these will affect ecosystem functioning.     

Flight initiation distance changes across landscapes and habitats in a successful urban coloniser

Urban Ecosystems - Urbanisation is a major land use change that introduces novel sources of disturbance and risk into an ecosystem. Successful urban species modify their fear behaviour in response...     

Wellbeing and urban living: nurtured by nature

Urban Ecosystems - In recent decades, empirical evidence has demonstrated that nature can enable urban environments to support human wellbeing. Research into links between nature and human...     

Focus groups identify optimum urban nature in four Australian and New Zealand cities

Urban residents and nature have often beneficial interactions, but there can also be conflict. We investigated the relationship between human wellbeing and nature in the two most-populous cities of both Australia and New Zealand. An online survey measured nature value orientations, and a selection of respondents who agreed to be contacted again were chosen based on their nature value orientation to invite to a focus group. This ensured that focus group participants represented a continuum of value orientations. Regardless of their nature value orientation, focus group participants were clear about needing nature in their city. They expressed strong opinions about how nature should be incorporated into the urban matrix to improve their lives. All focus groups described the integrated design of urban and natural elements when discussing positive experiences of nature in cities and had persistent concerns about how natural spaces are managed. While participants in different cities did discuss different landscape attributes and nature-related challenges, such as flooding, these differences did not affect the overall desire for nature in cities. We argue that urban design has the potential to ensure that residents engage with and experience nature in cities, and that design practices and policies could support the successful human-nature integration. Further research in other locations would determine how this work scales to either smaller towns and developed areas with smaller populations, or to mega-cities and other countries around the world.