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

Abstract

Given the predicted expansion of cities throughout the world, understanding the effect of urbanization on bee fauna is a major issue for the conservation of bees. The aim of this study was to understand how urbanization affects wild bee assemblages along a gradient of impervious surfaces and to determine the influence of landscape composition and floral resource availability on these assemblages. We chose 12 sites with a proportion of impervious surfaces (soil covered by parking, roads, and buildings) ranging from 0.06% to 64.31% within a 500 m radius. We collected using pan trapping and estimated the landscape composition of the sites within a 500 m radius and the species richness of plant assemblages within a 200 m radius. We collected 1104 bees from 74 species. The proportion of impervious surfaces at the landscape scale had a negative effect on wild bee abundance and species richness, whereas local flower composition had no effect. Ground‐nesting bees were particularly sensitive to the urbanization gradient. This study provides new evidences of the impact of urbanization on bee assemblages and the proportion of impervious surfaces at the landscape scale emerged as a key factor that drives those assemblages.

How does urbanization affect the reproductive characteristics and ecological affinities of street plant communities?

“…This interpretation is consistent with the decrease in wild bee abundance and richness, and the decreased number of plant-pollinator interactions with increasing percentage of impervious areas observed in the Parisian region (Desaegher et al, 2018;Geslin et al, 2013Geslin et al, , 2016. In particular, small-bodied floral visitors are more likely to be affected by urbanization because of reduced nesting opportunities (they are often ground-nesting) and limited flight capacities among suitable sites (Gathmann & Tscharntke, 2002;Geslin et al, 2016;Greenleaf, Williams, Winfree, & Kremen, 2007). It is possible that species bearing these types of flowers are more affected than the others by a general decrease in the abundance of pollinators.…”

“…We used the proportion of impervious areas around sampling sites as a measure of urbanization because it is obviously a major factor differentiating cities from other land uses, and because many studies have already used this measure (e.g., Ahrné, Bengtsson, & Elmqvist, 2009;Geslin et al, 2016;Pellissier, Muratet, Verfaillie, & Machon, 2012). We analyzed a dataset from a French national citizen science project called "Sauvages de ma rue" (literally "wild plants of my street") which aims at recording plant species growing spontaneously in the streets.…”

“…This region was chosen because (a) it was one of the most densely sampled area, (b) it included seminatural habitats distant from urban influences as well as highly urbanized landscapes, and (c) studies on the distribution of floral visitors (Desaegher et al, 2018;Geslin et al, 2016) and on plant-pollinator interactions (Desaegher, Nadot, Dajoz, & Colas, 2017;Geslin et al, 2013) in this region were already available. This region was chosen because (a) it was one of the most densely sampled area, (b) it included seminatural habitats distant from urban influences as well as highly urbanized landscapes, and (c) studies on the distribution of floral visitors (Desaegher et al, 2018;Geslin et al, 2016) and on plant-pollinator interactions (Desaegher, Nadot, Dajoz, & Colas, 2017;Geslin et al, 2013) in this region were already available.…”

“…Indeed, several studies have shown that urbanization affects pollinator communities along urbanization gradients (Baldock et al, 2015;Deguines, Julliard, Flores, & Fontaine, 2012;Fortel et al, 2014;Geslin et al, 2016). Indeed, several studies have shown that urbanization affects pollinator communities along urbanization gradients (Baldock et al, 2015;Deguines, Julliard, Flores, & Fontaine, 2012;Fortel et al, 2014;Geslin et al, 2016).…”

Massively Introduced Managed Species and Their Consequences for Plant–Pollinator Interactions

“…Cities are scheduled to increase by more than 250% in the next 15 years, with urbanization being one of the main drivers of habitat fragmentation and associated biodiversity losses (Concepcion et al, 2015;Geslin et al, 2016a;Nieto et al, 2014). Many towns are taking into account the importance of biodiversity and try to set up conservation measures.…”