Urban areas are often perceived to have lower biodiversity than the wider countryside, but a few small-scale studies suggest that some urban land uses can support substantial pollinator populations. We present a large-scale, well-replicated study of floral resources and pollinators in 360 sites incorporating all major land uses in four British cities. Using a systems approach, we developed Bayesian network models integrating pollinator dispersal and resource switching to estimate city-scale effects of management interventions on plant-pollinator community robustness to species loss. We show that residential gardens and allotments (community gardens) are pollinator ‘hotspots’: gardens due to their extensive area, and allotments due to their high pollinator diversity and leverage on city-scale plant-pollinator community robustness. Household income was positively associated with pollinator abundance in gardens, highlighting the influence of socio-economic factors. Our results underpin urban planning recommendations to enhance pollinator conservation, using increasing city-scale community robustness as our measure of success.
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. Competition for pollination is an important factor structuring flowering in many plant communities. We examined mechanisms reducing interspecific pollen flow in a community of 10 Acacia species in a highly seasonal savannah habitat in Tanzania. Partitioning is achieved, in part, through separation of flowering in space and seasonal time, and through interspecific differences in pollinator guilds. Nevertheless, coflowering Acacia species shared several pollinators; this means that interspecific pollen transfer is possible. We analyzed daily patterns of pollinator activity and pollen release in 10 Acacia assemblages containing a total of 10 Acacia species. Pollinator activity was scored using counts at flowers over constant time intervals throughout the day. Pollen availability was assessed using a simple method which allows quantification of pollen exposed on the surface of the Acacia inflorescence. Sympatric co-flowering Acacia species each show high intraspecific synchrony but release their pollen at different times of day. Pollinators rapidly harvest available pollen and move from one Acacia species to the next, following the daily sequence of pollen release. The activity of shared pollinators is structured throughout the day as a result of temporal patterns of pollen release across Acacia species. The observed temporal structuring of pollen release is compatible with patterns predicted to result from competitive displacement. Additional support for a competition-based explanation for this patterning comes from the observation that an Acacia species flowering without competitors shows no synchronized peak of pollen availability at any time of day. competition for pollinator visits in natural systems (Waser 1983, Rathcke 1983, 1988) and minimization of the costs associated with either mechanism of competition is thought to be an important force structuring plant communities (Pleasants 1983, Rathcke 1983, 1988, Waser 1983, Armbruster and Herzig 1984, Rathcke and Lacey 1985, Feinsinger 1987). An expected evolutionary consequence of competition is divergence along some resource axis (resource partitioning) to reduce the negative interaction between coexisting species (Brown and Wilson 1956, Pianka 1973, Schoener 1983). Four resource axes have received attention. First, plants may differ in the pollinators they recruit (axis 1), and so have independent vectors of pollen transfer (Heinrich 1976, Inouye 1978, Pleasants 1983, Armbruster and Herzig 1984, Rathcke 1988). However, pollinator guilds of plant species often overlap and many studies have examined mechanisms th...
How widespread ecological communities assemble remains a key question in ecology. 1Trophic interactions between widespread species may reflect a shared population history, 2 or ecological sorting of local pools of species with very different population histories. 3Which scenario applies is central to the stability of trophic associations, and the 4 potential for coevolution between species. Here we show how alternative community 5 assembly hypotheses can be discriminated using whole genome data for component 6 species, and provide a novel likelihood framework that overcomes current limitations in 7 formal comparison of multispecies histories. We illustrate our approach by inferring the 8 assembly history of a Western Palaearctic community of insect herbivores and 9 parasitoid natural enemies, trophic groups that together comprise 50% of terrestrial 10 species. We reject models of co-dispersal from a shared origin, and of delayed enemy 11 pursuit of their herbivore hosts, arguing against herbivore attainment of 'enemy-free 12 space'. The community-wide distribution of species expansion times is also incompatible 13 with a random, neutral model of assembly. Instead, we reveal a complex assembly 14 history of single-and multi-species range expansions through the Pleistocene from 15 different directions and over a range of timescales. Our results suggest substantial 16 turnover in species associations, and argue against tight coevolution in this system. The 17 approach we illustrate is widely applicable to natural communities of non-model species, 18 and makes it possible to reveal the historical backdrop against which selection acts.
Summary:The chestnut gall wasp Dryocosmus kuriphilus is a global pest of chestnut (Castanea). Established as a pest in the mid 20th century in Japan, Korea and the USA, this species has now reached Europe. Successful deployment of a biocontrol agent, Torymus sinensis, in Japan has led to its early release in Italy. Here we provide the first overview of the natural enemies associated with D. kuriphilus in its native and invaded ranges, and discuss general patterns in community development. We then use what is known about European oak gall wasp communities to predict possible future developments for D. kuriphilus, and possible interactions between parasitoid communities attacking hosts on chestnut and oaks.
The Library Impact Data Project was a six-month project funded by Jisc and managed by the University of Huddersfield to investigate this hypothesis: “There is a statistically significant correlation across a number of universities between library activity data and student attainment.” E-resources usage, library borrowing statistics, and library gate entries were measured against final degree award for 33,074 undergraduate students across eight U.K. universities. The research successfully demonstrated a statistically significant relationship between library resource use and level of degree result; however, any conclusions drawn are not indicators that library usage and student attainment have a causal relationship.
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