Drivers of specialist herbivore diversity across 10 cities

Patterns of Insect Abundance and Distribution in Urban Domestic Gardens in Bangalore, India

“…Thus, multiple factors appear to be responsible for shaping the abundance and diversity of insects in Bangalore's home gardens, as also observed in other urban ecological studies, e.g., of the drivers of herbivore distribution in cities in California [31]. Since Hymenoptera constitutes by far the most abundant insect order encountered, the preponderance of this order may be driving many of the relationships we encounter between insect abundance and garden variables; thus we suggest that further research be conducted specifically focusing on Hymenoptera.…”

Insects in Urban Environments

“…Sax and Gaines suggested that such local diversity increases might be more common than decreases, and could lead to possibly detrimental and largely unknown impacts on community processes and ecosystem functioning. Gall wasp communities, based on the 22 most easily recognised species of cynipoid wasps feeding on a white oak , Quercus lobata , were compared across 10 cities of California's central valley (Herrmann et al 2012 ). Q. lobata is an important host for numerous specialist insect herbivores, and the relationships between the tree and its gall wasps (which variously make galls on foliage, buds or stems) were considered an ideal system through which to study how such a restricted insect community can change with host features that may differ (1) among trees within a city, and (2) between urban and natural areas.…”

“…They also have the study advantage that they are not regarded as pests and are thus generally overlooked by people to whom the insects otherwise might be targeted for suppression, as are some other taxa on street trees (p. 111). Sampling was by direct inspection of trees (137 in all) from three types of ground cover: mostly natural litter, managed (such as lawns or raked earth) and paved, and gall abundance was the summed count from two observers (Herrmann et al 2012 ) and compared across urban and natural areas. Urban areas were associated with reduced wasp diversity but, despite consistently lower richness and diversity of the communities in urban areas, the species lost were not the same ones across different cities, or even across different trees in the same city.…”

“…The regional species pool sets limits to any contained local assemblage, with intraregional differences indicating potential for different assemblages to occur. Each patch comprises the host tree and local ground cover (leaf litter), with dispersal between patches in a local landscape within which a network of patches is nested (Herrmann et al 2012 ) with declining richness and increased vulnerability of assemblages to invasions by alien species. Many birds (and others) in cities depend largely on insects for food, so that management of trees (in particular) to enable insect abundance is necessary.…”

Countering Insect Habitat Losses and Change in Urban Areas

“…Even for those, control of trophic interactions in a novel environment may be minimal. Native plant communities in cities are restored or maintained for a variety of purposes: Herrmann et al ( 2012 ) noted re-creating structure, resources and ecological processes to support native species in complex food webs -but without those native species, biotic impoverishment is largely assured.…”