Are cities hotspots for bees? Local and regional diversity patterns lead to different conclusions

Weronika Banaszak-Cibicka,Michał Żmihorski

doi:10.1007/s11252-020-00972-w

Abstract

With the decline of natural habitats, there is an ongoing debate about the importance of the urban environment for pollinating insects. Our research assessed patterns in wild bee species composition, as well as α-, β- and γ-diversity patterns and the nestedness structure in urban, suburban and rural areas. For three years bees were collected along 18 sampling transects in the Poznań area in western Poland. The average species diversity (α-diversity) and the average number of specimens per sample (local abundance) did not differ significantly between the three classes of urbanization. The rarefaction analysis, however, was partly contradictory to the results recorded on the local scale. The highest dissimilarity in the species composition among the samples was observed in the rural areas, while the lowest (more homogenous) was in the urban areas. The differences were significant. This resulted in the highest γ-diversity (cumulative number of species) in the rural areas and the lowest in the urban areas. Furthermore, the bee community in the habitats studied was significantly nested, indicating that species-poor sites (sites with high rank) constituted subsets of species-rich sites (sites with low rank) and that this pattern was not random. Samples collected in urban areas had a significantly higher nestedness rank compared to samples from the other two classes of urbanization, thus suggesting that the urban bee community is a subset of the rural bee community. This is an important conclusion, which emphasises that different components of species diversity need to be screened to identify the real biological impact of urbanisation on bee communities.

Highlights

In recent decades, the diversity of wild bees has declined markedly worldwide due to environmental changes (Biesmeijer et al 2006; Fitzpatrick et al 2007; Potts et al 2010; Cameron et al 2011; Ollerton et al 2014)
Apart from common species, 24 species (13.6% of the total number of species recorded) that are on the Red List of Threatened Species in Poland were recorded (Banaszak 2002). They are classified as vulnerable (VU) – 8 species: Hylaeus rinki (Gorski, 1852), Andrena falsifica Perkins, 1915, Andrena florea Fabricius, 1793, Andrena limata Smith, 1853, Anthocopa papaveris (Latreille, 1799), Proanthidium oblongatum Latreille, 1809, Bombus jonellus (Kirby, 1802), Bombus veteranus (Fabricius, 1793), data deficient (DD) – 13 species: Colletes similis Schenck, 1853, Hylaeus bisinuatus Förster, 1871, Hylaeus cornutus Curtis, 1831, Hylaeus gracilicornis (Morawitz, 1867), Hylaeus gredleri Főrster, 1871, Hylaeus pictipes Nylander, 1852, Hylaeus signatus (Panzer, 1798), Andrena bimaculata (Kirby, 1802), Dufourea minuta Lepeletier, 1845, Evylaeus brevicornis (Schenck, 1863), Seladonia semitecta (Morawitz, 1874), Coelioxys alata (Förster, 1853), Nomada bifasciata Olivier, 1811, least concern (LC) – 3 species: Megachile nigriventris Schenck, 1868, Nomada moeschleri Alfken, 1913, Nomada zonata Panzer, 1798
Our study showed that the pooled γ-diversity of wild bees was substantially larger in the rural landscape than in cities, while nestedness analysis suggests that local urban bee communities constitute, to some extent, subsets of bee communities found in suburban and rural areas

Summary

Introduction

The diversity of wild bees has declined markedly worldwide due to environmental changes (Biesmeijer et al 2006; Fitzpatrick et al 2007; Potts et al 2010; Cameron et al 2011; Ollerton et al 2014). The decline of wild bees and possible mitigating measures have attracted considerable attention among conservation biologists all over the world

Methods

Results

Discussion

Conclusion