Functional homogenization of flower visitor communities with urbanization

Abstract

Land‐use intensification and resulting habitat loss are put forward as the main causes of flower visitor decline. However, the impact of urbanization, the prime driver of land‐use intensification in Europe, is poorly studied. In particular, our understanding of whether and how it affects the composition and functioning of flower visitor assemblages is scant, yet required to cope with increasing urbanization worldwide. Here, we use a nation‐wide dataset of plant‐flower visitor (Coleoptera, Diptera, Hymenoptera, Lepidoptera) interactions sampled by citizen scientists following a standardized protocol to assess macroecological changes in richness and composition of flower visitor communities with urbanization. We measured the community composition by quantifying the relative occurrence of generalist and specialist flower visitors based on their specialisation on flowering plant families. We show that urbanization is associated with reduced flower visitor richness and a shift in community composition toward generalist insects, indicating a modification of the functional composition of communities. These results suggest that urbanization affects not only the richness of flower visitor assemblages but may also cause their large‐scale functional homogenization. Future research should focus on designing measures to reconcile urban development with flower visitor conservation.

The origin of urban communities: From the regional species pool to community assemblages in city

“…While several studies suggest that urbanization leads to biotic homogenization (Deguines et al, ; Groffman et al, ; McKinney, ), evidence that city harbours unique species assemblages also exists (Sattler et al, ; Swan, Johnson, & Nowak, ). Our results provide mixed evidence for this issue.…”

“…McDonnell & Hahs, ; McDonnell & Pickett, ) suggesting that high degrees of urbanization promote the loss of native species and the establishment of non‐native species (McKinney, ) leading to biotic homogenization (e.g. Deguines, Julliard, Flores, & Fontaine, ; Knop, ; McKinney & Lockwood, ). Another approach focuses on community patterns and mechanisms within cities highlighting the importance of area (Beninde, Veith, & Hochkirch, ), connectivity (Beninde et al, ; Braaker, Ghazoul, Obrist, & Moretti, ), and heterogeneity within and among UGS (Lepczyk et al, ; Tonteri & Haila, ) for urban biodiversity.…”

The city as a refuge for insect pollinators

“…[], and Deguines et al. []). For bumblebees in particular, urban areas can harbor greater species richness than rural or natural areas (McFrederick & LeBuhn ; Winfree et al.…”

Context Matters: Contrasting Ladybird Beetle Responses to Urban Environments across Two US Regions

“…Non-native species to a region often have a greater ability to survive in a variety of habitats-including disturbed habitats-than native species [74]. In disturbed urban landscapes, more abundant species are habitat generalists and/or non-native to a region [2,75]. These species have ecological traits that allow them to exploit resources and persist [76], and environmental filters have been used to explain taxonomic differences between urban habitats [12,77].…”