As urbanization intensifies, urban ecosystems are increasingly under pressure from a range of threats. Horizon scanning has the potential to act as an early warning system, thereby initiating prompt discussion and decision making about threat mitigation. We undertook a systematic horizon scanning exercise, using a modified Delphi technique and experts from wide‐ranging disciplines, to identify emerging threats in urban ecosystems. The 10 identified threats were generally associated with rapid advances in technology (eg solar panels, light‐emitting diode lights, self‐healing concrete) or with societal demands on urban nature (eg green prescriptions). Although many of the issues identified are also technological opportunities with recognized environmental benefits, we have highlighted emerging risks so that research and mitigation strategies can be initiated promptly. Given the accelerated rate of technological advancement and the increasing demands of urbanized populations, horizon scanning should be conducted routinely for urban ecosystems.

The interaction between Depressaria pastinacella (parsnip webworm) and wild parsnip ( Pastinaca sativa ), in its native Europe and in its longstanding nonindigenous range in the midwestern United States, is characterized by chemical phenotype matching, ostensibly mediated by reciprocal selective responses. The first appearance of D. pastinacella on P. sativa in New Zealand in 2004 provided an opportunity to quantify selective impacts of a coevolved herbivore and calibrate rates of phytochemical response in its host plant. Webworms in 2006 reduced seed production up to 75% in New Zealand populations, and in 2007 infestations increased in severity in all populations except one. Most New Zealand populations fall into a furanocoumarin phenotype cluster distinct from European and U.S. phenotypes, although one heavily attacked population clusters with two U.S. populations and one European population long associated with webworms. Multivariate selection analysis substituting realized fitness (with webworms present) for potential fitness (absent webworms) as the dependent variable revealed that reassociation with a coevolved specialist in a nonindigenous area profoundly altered the selection regime, favoring trait remixing and rapid chemical changes in parsnip populations, as predicted by the geographic mosaic theory. That uninfested populations of New Zealand parsnips contain higher amounts of octyl acetate, a floral volatile used by webworms for orientation, suggests that plants that escape from specialized enemies may also experience selection to increase kairomones, as well as to reduce allomones.

The practice of garden bird feeding is a global phenomenon, involving millions of people and vast quantities of food annually. Many people engage in the practice of feeding assuming that birds gain some benefit from the food they provide, yet recent studies have revealed the potential for detrimental impacts as well. However, there is still a paucity of information on the impacts of feeding, including the ubiquity of these impacts among and within feeder-visiting species. Consistency in feeder use among birds is likely an important determinant of this. Individual birds and species that make frequent use of feeders are more likely to experience both the benefits and detrimental impacts of supplementary food. We investigated patterns of feeder use by garden birds visiting experimental feeding stations in Auckland, New Zealand, with the specific aim of determining whether use of supplementary food was consistent or variable among individuals and species. We used camera traps as well as Radio Frequency Identification (RFID) technology to examine intra- and interspecific feeder visitation patterns and to discern species associations. Eleven bird species were detected using feeding stations, however, two introduced species (house sparrow Passer domesticus and spotted dove Streptopelia chinensis) dominated visitation events. These species were present at feeders most frequently, with the largest conspecific group sizes. Significant associations were detected among a number of species, suggesting interspecific interactions are important in determining feeder use. We also found within-species differences in feeder use for all focal species, with individual variation greatest in house sparrows. Furthermore, season had an important influence on most visitation parameters. The observed individual and species-specific differences in supplementary food resource use imply that the impacts of garden bird feeding are not universal. Crucially, particularly given the avifaunal context in New Zealand, resource dominance by introduced species could have potential negative outcomes for native species conservation in cities.

Overlap in the form of sexual signals such as pheromones raises the possibility of reproductive interference by invasive species on similar, yet naive native species. Here, we test the potential for reproductive interference through heterospecific mate attraction and subsequent predation of males by females of a sexually cannibalistic invasive praying mantis. Miomantis caffra is invasive in New Zealand, where it is widely considered to be displacing the only native mantis species, Orthodera novaezealandiae , and yet mechanisms behind this displacement are unknown. We demonstrate that native males are more attracted to the chemical cues of introduced females than those of conspecific females. Heterospecific pairings also resulted in a high degree of mortality for native males. This provides evidence for a mechanism behind displacement that has until now been undetected and highlights the potential for reproductive interference to greatly influence the impact of an invasive species.