The spatial distribution of phytophagous insect larvae in grassland soils

Most research on soil dwelling phytophagous insect larvae has arisen from their functional roles as pests in agricultural systems, but few studies have considered their spatial distribution or the possible interactions between taxa, and none have investigated the effect of scale. In this study the individual and interspecific spatial distribution of wireworms (click beetle larvae - Elateridae), leatherjackets (crane fly larvae - Tipulidae), bibionid flies (Bibionidae) and sciarid flies (Sciaridae) over three scales, and the importance of spatial, biotic and scale variables, was assessed. Soil core samples were collected from 26 sites across six grass fields on a farm in South Devon, UK. Abundance and presence-absence data were analysed over the field, site and soil core scales using variance/mean ratio and non-metric multidimensional scaling (NMDS), and deviance partitioning was used to determine the importance of spatial, biotic and scale variables for individual taxa distribution. The spatial distribution of most taxa changed from an aggregated to a random distribution from the field to the core scale. Interspecific distributions of taxa also differed between scales, though some associations held at all scales. Deviance partitioning revealed that scale was the single most important variable influencing taxa distribution, whereas spatial and biotic variables were mostly of minor importance. The results suggest that variation between taxa is likely to be due to interactions between scale-specific environmental, biotic and stochastic factors and individual taxon biology, and emphasises the need to take scale into account when interpreting data from ecological studies. (C) 2010 Elsevier B.V. All rights reserved.