Insects on urban plants: contrasting the flower head feeding assemblages on native and exotic hosts

Abstract

Exotic plant species very often comprise a large proportion of urban floras. Because herbivorous insects depend on the presence of suitable host plants to maintain their populations, it is imperative to elucidate the relative importance of native and exotic hosts to understand the response of herbivorous guilds to urbanization. By using a plantherbivore system composed of Asteraceae hosts and flower-head endophagous insects, we investigated whether the diversity and composition of herbivorous insects differs between native and exotic host-plant species in an urban environment. Although we found only seven exotic Asteraceae among the 30 species recorded, the overall abundance of exotics was considerably greater than that of native host plants. Overall, the exotic host species supported a small subset of the herbivore assemblage found on the native ones. The number of herbivore species per host species was significantly higher among the native plants, but we did not find a difference in herbivore abundance. Moreover, the higher taxonomic composition of herbivores on exotic Asteraceae was reduced, being composed of only three genera and two families from a total of 16 genera and six families of herbivores. These results provide support for the idea that plants outside of their original geographic distribution have lower loads of enemies than phylogenetically related native species. Our findings indicate that native host plants in urban areas play a critical role in supporting the native herbivorous insect fauna.

The proportion of impervious surfaces at the landscape scale structures wild bee assemblages in a densely populated region

“…); for example, city gardens are often planted with horticultural or ornamental plants, which artificially increase species richness and change the composition of plant assemblages (McKinney ; Perre et al. ). In some cases, pollinators have been described to visit those exotic plants within cites (Hanley et al.…”

“…Thus, the structure of urban plant assemblages may not directly relate the structure of pollinator assemblages. Indeed, urbanization promotes the loss of native species and their replacement by non-native ones (e.g., Bergerot et al 2010;Goddard et al 2010); for example, city gardens are often planted with horticultural or ornamental plants, which artificially increase species richness and change the composition of plant assemblages (McKinney 2008;Perre et al 2011). In some cases, pollinators have been described to visit those exotic plants within cites (Hanley et al 2014;Salisbury et al 2015), even if native plants seemed to be preferred (Corbet et al 2001;Williams et al 2011) and to be a better descriptor of pollinator communities (Burghardt et al 2009;Pardee and Philpott 2014).…”

Patterns of Bat Distribution and Foraging Activity in a Highly Urbanized Temperate Environment

“…We identified potential habitat-related explanatory variables for each park site based on those reported in other studies of urban bats, including park size (“Pk Size”) [22], amount of forest edge (“Edge”) [8, 36, 37], percent native habitat (“Native”) [70], distance to the nearest large park (“Lg Pk”) [22], and distance to nearest water (“Water”) [39, 40, 71]. Models including distance-based variables are more accurate than those including only within-park variables [72].…”

Survey of insect visitation of ornamental flowers in Southover Grange garden, Lewes, UK

“…For example, butterfly larvae typically have a narrow range of suitable food plants (Dyer et al ., ). Plants grown outside their original geographic distribution often support fewer herbivores than closely related native species (Perre et al ., ). However, introduced plants also have generic value to wildlife, such as a bird that can nest in an introduced tree as easily as in a native one.…”