Large-scale Spatial Patterns in Species Richness of Orthoptera in the Greater London Area, United Kingdom: Relationships with Land Cover

Abstract

This paper explores species richness of insects of the Order Orthoptera along spatial gradients defined using remotely sensed land cover data for an area of 5,600 km 2 centred on the city of London. The numbers of species within grid-squares of a national atlas, controlled for recording effort, declined along composite multivariate spatial gradients representing landscapes with increasing dominance of arable and urban land uses, yet was uncorrelated with the area of an individual land cover representing cultivated land and only weakly correlated with area of a second land cover representing urban development. Few orthopteran species reside directly within either arable crops or non-vegetated urban land covers. Thus, whilst the areas of the individual land covers are intuitively sensible (and simple) measures of agricultural and urban cover respectively, their areas do not capture ecologically relevant information about variation in the composition of the uncultivated and non-urban land cover matrices within which the species actually reside. The results illustrate the advantages of using multivariate data reduction techniques (such as the Principle Components Analysis applied here) to describe spatial gradients in the extent of agricultural and urban influence. Relatively few landscape scale studies have focussed on insects and the present study illustrates a) the potential for using the Orthoptera to explore and monitor impacts of land use via analysis of large scale spatial patterns from national species distribution atlases combined with remotely sensed land cover, and b) the importance of selecting appropriate measures of land use which incorporate information on the complex mix of land cover types utilised by the species under investigation.3

Impact of urbanization on predator and parasitoid insects at multiple spatial scales

“…Studies exploring the effects of urbanization on flower-visiting species have also revealed mixed responses. Some species decline and become locally extinct in urban areas [2,18,20,21], whereas others remain common in highly disturbed habitats [3,4,9,10,13]. Several studies suggested that flower-visitors are affected by the availability and diversity of foraging and nesting resources rather than urbanization intensity itself [2,18,20–22,35,54].…”

“…On the other hand, some species can exploit the resources available in urban areas and are able to survive in highly disturbed habitats [4,8–10,13,48,54]. For example, nesting bees and wasps [3,4,10], as well as other generalist insect species [18,33], have been shown to benefit from urbanization. Here, we found that at the landscape scale the percentage of urban area decreased abundance and increased evenness of sphecids.…”

“…Rapid demographic and economic growth has led to increased urbanization and agricultural intensification [1–3]. Consequently, large areas of natural and semi-natural habitats have been extensively modified to make space for urban, industrial and agricultural areas.…”

“…Urbanization impact can occur at multiple spatial scales [3,4,7,16,30] and species responses depend on properties of the environment as well as on species traits [15,28,32–35]. In general, the increase in urbanization is expected to negatively influence insect movements [23], and exacerbate spatial mismatch between predators/parasitoids and their resources [4,27].…”

Linking mesoscale landscape heterogeneity and biodiversity: gardens and tree cover significantly modify flower-visiting beetle communities

“…However, whilst landscape conservation or landscape planning tends to consider landscape from an anthropogenic point of view, perhaps at a kilometreswide scale, there is no single 'landscape scale' relevant to all species groups (Schweiger et al 2005;Ekroos et al 2013;Fuentes-Montemayor et al 2017). Highly mobile species groups such as birds or Orthoptera respond to landscape composition even when examined at fairly broad scales, e.g., cricket species richness in 10-km 2 (Cherrill 2015) or bird community composition in 2-km tetrads (Neumann et al 2016a). For invertebrates with more limited dispersal power, landscape heterogeneity within a radius of hundreds of metres is important, as seen for ground beetles (Carabidae) at a 400-m radius (Barbaro et al 2007; Barbaro and Van Halder 2009) and Lepidoptera, hoverflies (Syrphidae) and bees at 600 m (Sjödin et al 2008).…”