Flower-visitor and pollen transport networks in a large city: structure and properties

Abstract

Plant species and their pollinators are linked by their mutualistic interactions, which form the basis of pollination networks. The use of a network approach allows one to take into account all interactions between a group of plants and its animal pollinators, and to reveal the structure of these connections. We analysed pollination interactions for urban habitat fragments located within the Warsaw city environment. We compared two similar, ruderal communities (phytosociological order Onopordetalia acanthii) located in distant parts of the city of Warsaw (Poland) that differed with the surrounding ecosystems. The aim of this study was to define the structures and properties of flower-visitor (visitation) and pollen transport networks (based on analysis of pollen loads carried by insects) and to assess the differences between the studied sites. Although the sites differed in insect relative abundance (Diptera dominated one study site, whereas Hymenoptera dominated the other), network size and structure were similar for both communities. In both cases, networks contained moderately specialized species (based on H 2 0 index); however, networks were dominated by apparently ecologically generalized insect taxa as well as those represented by a single specimen. Networks based on pollen transport indicated greater generality of insect species (more links) than those based on our samples of visitation. The most highly linked plant species represented were either the most abundant (Fabaceae) or phenotypically generalized taxa (Daucus carota). We conclude that plantpollinator interactions in such highly disturbed and isolated habitats are composed mostly of ecologically generalised species. Moreover, we stress the usefulness of pollen load analysis in the development and verification of visitation data.

Wild bees as pollinators of city trees

“…With increasing urbanity, an increase in the number of social species and a decrease in the number of parasitic species were observed by two studies (Fetridge & Ascher, ; Banaszak‐Cibicka & Żmihorski, ). In the city of Warsaw, Jędrzejewska‐Szmek and Zych () found mainly generalist bee species to dominate the pollinator community.…”

Railway embankments - a refuge areas for food flora, and pollinators in agricultural landscape

“…The high attractiveness of P. sativa is presumably related to both its high frequency and abundance on railway embankments. A positive dependence between plant abundance and the number of established links with insect visitors was revealed, for example, by Jędrzejewska-Szmek and Zych (2013). The important role of the Apiaceae species as a food resource for a variety of insect visitors especially for flies, beetles, and the wasp species was stressed in several studies (e.g.…”

“…The preference of honeybees to species which flowered abundantly resulted in a high nectar and/or pollen yield per unit area over a short period of time, and was noted by e.g. Steffan-Dewenter & Tscharntke (2000), Denisow (2011), andJędrzejewska-Szmek &Zych (2013).…”

Evaluation of Selected Ornamental Asteraceae as a Pollen Source for Urban Bees

“…The main visitors to the studied flowers were polylectic bees. Several urban bee surveys indicate that generalist bee species with broad tolerance are favoured in urban areas (Matteson & Langelotto, 2011;Banaszak-Cibicka & Żmihorski, 2012); however the persistence of specialist species is also possible (Jędrzejewska-Szmek & Zych, 2013). The interest shown by the insects in the forage as well as formation of pollen loads (C. macrocephala, C. officinalis, C. sulphureus, D. pinnata) provide evidence of the attraction held by those plants for both domesticated and wild bees.…”

“…Land-use change with the loss of floral and nesting resources is generally thought to be the most important contributor to various disturbances in wild bee abundances and species richness (Winfree et al, 2009). However, current studies have shown that cities could be pollinator reservoirs with a higher biodiversity of pollinating insects within them, as compared to the countryside (Goulson et al, 2010;Banaszak-Cibicka & Żmihorski, 2012;Jędrzejewska-Szmek & Zych, 2013). High plant species diversity is characteristic of several urban areas.…”