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

This paper explores species richness of insects of the order Orthoptera (grasshoppers, crickets, etc.) along spatial gradients defined using remotely sensed land cover data for an area of 5600?km² centred on the city of London. The number 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 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 focused on insects and the present study illustrates a) the potential for using Orthoptera to explore issues of biodiversity in the landscape and to 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.