Roles of scale, matrix, and native habitat in supporting a diverse suburban pollinator assemblage

Abstract

Wild pollinators provide important services to both wild and human-dominated ecosystems, yet this group may be threatened by widespread anthropogenic landscape change. Suburban sprawl is one of the fastest growing types of land use change in North America, and it has certain characteristics, such as abundant floral resources, that may be beneficial for many pollinators. We examined the effects of sprawl on the wild bee assemblage of the shortgrass steppe on the Front Range of Colorado, USA. Diversity, abundance, and community composition of bees in remnant grassland fragments surrounded by suburban residential land use were compared with those in extensive, continuous grassland. No overall effect of suburbanization on bee abundance was observed, and abundance was extremely variable even within study sites. Bee species richness was positively but nonlinearly related to grassland habitat area. Bee species density was higher and more variable in suburban sites. Suburban sites and smaller habitat area were both related to relative increases in the proportions of small bee species, social bees, and solitary cavity-nesting bees in the assemblage; small suburban habitat areas also favored species of the family Halictidae over Apidae, and individuals of the genus Halictus over those of the genus Lasioglossum. In this landscape, large native habitat areas surrounded by suburban sprawl may actually increase species richness and species density over that of continuous grassland, probably by means of habitat complementation or supplementation between grassland remnants and the surrounding suburban matrix. However, at habitat areas < 20 ha, species richness became quite variable; sites < 8 ha contained less than half the species of controls.

City parks vs. natural areas - is it possible to preserve a natural level of bee richness and abundance in a city park?

“…Such correlation has also been observed in beetles and spiders (Miyashita et al 1998;Weller and Ganzhorn 2004). Large size is a correlate of extinction risk in many groups, including some bee communities (Flynn et al 2009;Hinners et al 2012). Lower abundance of late spring species might, in turn, be related to the fact that a considerable part of lawns in the city park is regularly mowed.…”

Diversity and abundance of solitary and primitively eusocial bees in an urban centre: a case study from Northampton (England)

“…In a review, Hernandez et al (2009) found only 59 research publications worldwide on urban bee ecology and concluded that we are only beginning to document urban bee communities and their dynamics. The interest in urban bee ecology has surged in recent years (Everaars et al 2011;Winfree et al 2011;Hennig and Ghazoul 2012;Banaszak-Cibicka and Zmihorski 2012;Hinners et al 2012;Matteson et al 2013;Verboven et al 2014;Lowenstein et al 2014;Baldock et al 2015). However urbanisation is predicted to increase dramatically, with the number of people living in urban areas reaching 5 billion by 2030 (UN 2011).…”

Flowering phenology and nesting resources influence pollinator community composition in a fragmented ecosystem

“…In landscapes with high variation in temporal and spatial distribution of floral resources, species may benefit by tracking the availability of resources in different landscape components over time Mandelik et al 2012;Tarrant et al 2013). For example, increased abundance and diversity of small-bodied generalist bees in natural habitat fragments surrounded by urban development is hypothesized to be due to use of floral resources in residential gardens in the urban matrix (Hinners et al 2012, Wray et al 2014, but this has not been explicitly tested. In contrast, floral specialists may not benefit from resources in the matrix, a hypothesis that could be evaluated if the matrix was included in sampling designs.…”