The effect of urbanization on the quality of remnant habitats for leaf‐mining Lepidoptera on Quercus agrifolia

Abstract

2003. The effect of urbanization on the quality of remnant habitats for leaf-mining Lepidoptera on Quercus agrifolia. -Ecography 26: 777-787.Previous studies suggest that urbanization alters the abundance and species richness of native insects on remnant habitat patches. However, the effects of urbanization on biological communities caused by habitat loss and fragmentation have not been separated from effects caused by altered habitat quality within remnant habitats or by the nature of the urban matrix. To test for an effect of urbanization acting via altered habitat quality or matrix characteristics, we controlled for the effects of habitat loss and fragmentation by comparing remnant habitat patches in urban and agricultural regions experiencing similar levels of habitat loss and fragmentation. We studied the species richness and abundance of the community of leaf-mining Lepidoptera on Quercus agrifolia in the San Francisco Bay Area. We measured the extent of five land-use types within a 500 m radius of each study patch. We built generalized linear models to determine if the extent of any of the landscape variables was associated with the species richness and abundance of the leaf-miner community. The extent of urbanization was not associated with species richness or total abundance. However, the abundance of three species of leaf-mining moths was associated with the extent of urbanization, but not in a consistent pattern. The abundances of Stigmella 6ariella and Bucculatrix albertiella were higher and the abundance of Dryseriocrania auricyanea was lower at highly urbanized sites. The absence of a consistent association between urban land-use and both species richness and abundance indicates that the effects of urbanization on the community of leaf-mining moths of Q. agrifolia do not differ from the effects of replacing and fragmenting habitats with similar amounts of agricultural land-uses.

Effects of habitat and landscape fragmentation on humans and biodiversity in densely populated landscapes

“…In contrast, species richness and total abundance of leaf-mining moths on oaks (Quercus agrifolia) were not affected by urban land-use. These small insects can maintain large populations in relatively small patches of one to several oak trees (Rickman and Connor, 2003). In summary, urban land-use seems to effectively separate populations of vagile animals, but may not necessarily affect small and sedentary animals.…”

Natural, not urban, barriers define population structure for a coastal endemic butterfly

“…Indeed, one study showed that the effects of fragmentation resulting from urbanization on insects were no different than fragmentation resulting from agriculture (Rickman and Connor 2003). In agricultural landscapes, research on ''countryside biogeography'' provides compelling evidence that forest fragments can retain species diversity for several taxa, and even benefit surrounding agricultural areas via ecosystem services such as pollination Ricketts et al 2001;Daily et al 2003;Horner-Devine et al 2003).…”

Urbanization affects the trophic structure of arboreal arthropod communities

“…Although assessments of the ecological consequences of urbanization have historically been survey-based, with a strong bias towards vertebrates and dominant plants, there has been a recent shift in focus to determine the responses of terrestrial invertebrates (Nuckols and Connor 1995;Niemelä et al 2002;Clarke et al 2007;Scanlon and Petit 2008) as a means to understanding how urbanization affects ecosystem function. Invertebrate responses to urbanization have been found to be highly variable across taxa and are often linked to disruptions of ecological processes (Hatcher and Ayres 1997;McIntyre and Hostetler 2001;Rickman and Connor 2003;Christie and Hochuli 2009). For example, ecosystem functioning may be significantly affected by changes in arthropod communities as shifts occur in community composition (Bolger et al 2000;Niemelä et al 2000;Hochuli et al 2004;Ryall and Fahrig 2005).…”