Disentangling urban habitat and matrix effects on wild bee species.

Leonie K Fischer,Sascha Buchholz,Ingo Kowarik,Julia Eichfeld

doi:10.7717/peerj.2729

Leonie K Fischer, Sascha Buchholz + Show 2 more

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https://doi.org/10.7717/peerj.2729

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Abstract

In face of a dramatic decline of wild bee species in many rural landscapes, potential conservation functions of urban areas gain importance. Yet effects of urbanization on pollinators, and in particular on wild bees, remain ambiguous and not comprehensively understood. This is especially true for amenity grassland and extensively managed wastelands within large-scale residential housing areas. Using Berlin as a study region, we aimed to investigate (a) if these greenspaces are accepted by wild bee assemblages as foraging habitats; (b) how assemblage structure of bees and individual bee species are affected by different habitat (e.g., management, flower density) and urban matrix variables (e.g., isolation, urbanization); and (c) to what extent grassland restoration can promote bees in urban environments. In summer 2012, we collected 62 bee species belonging to more than 20% of the taxa known for Berlin. Urbanization significantly affected species composition of bees; 18 species were affiliated to different levels of urbanization. Most bee species were not affected by any of the environmental variables tested, and urbanization had a negative effect only for one bee species. Further, we determined that restoration of diverse grasslands positively affected bee species richnesss in urban environments. We conclude that differently structured and managed greenspaces in large-scale housing areas can provide additional foraging habitats and refuges for pollinators. This supports approaches towards a biodiversity friendly management within urban regions and may be of particular importance given that anthropogenic pressure is increasing in many rural landscapes.

Highlights

The observed dramatic decline of wild bee species richness and abundances during the last decades (Potts et al, 2010; Carvalheiro et al, 2013)—especially in rural landscapes—is of great concern due to the enormous agricultural, ecological and cultural value (Gallai et al, 2009; Ollerton, Winfree & Tarrant, 2011) of bees
Results from the generalized linear models (GLM) indicated that species showed multidirectional responses to environmental variables (Fig. 4)
Urbanization, management and plant species richness had more positive than negative effects

Summary

Introduction

The observed dramatic decline of wild bee species richness and abundances during the last decades (Potts et al, 2010; Carvalheiro et al, 2013)—especially in rural landscapes—is of great concern due to the enormous agricultural, ecological and cultural value (Gallai et al, 2009; Ollerton, Winfree & Tarrant, 2011) of bees. How to cite this article Fischer et al (2016), Disentangling urban habitat and matrix effects on wild bee species. It is widely assumed that cities can provide suitable secondary habitats for a variety of invertebrate species (Lundholm & Richardson, 2010; Jones & Leather, 2012; Shwartz et al, 2014). This is because urban areas offer a unique ecological environment with warm climate and high habitat diversity leading to diverse nesting and foraging opportunities (Ahrné, Bengtsson & Elmqvist, 2009; Sattler et al, 2010). Plant species richness is usually higher in urban than in rural areas (Kühn, Brandl & Klotz, 2004) and flowers— which are less often treated with pesticides than flowers in agricultural areas (Hostetler & McIntyre, 2001)—are available abundantly throughout the year (Fetridge, Ascher & Langellotto, 2008)

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