Guild Structure in the British Arboreal Arthropods: Is it Stable and Predictable?

Abstract

The British arboreal arthropods were cross-classified into four guild and fifteen taxonomic categories, examined for patterns of variation among twenty-eight tree species and variously analyzed in relation to relevant host tree attributes; both varied widely. The porportion of species in the ''chewers'' guild increased on more abundant, taxonomically related hosts with 46% of guild variation explained by these attributes. Other tested attributes had no effect on this guild, and sap-feeders, leaf-miners and gallformers were either marginally or not at all influenced by any host attribute. Neither evergreenness nor palatability accounted for any residual guild variation. Guilds increased or decreased in richness independently of one another with one exception: sap-feeders and chewers guilds increased in parallel. There was little tendency for tree species having similar guild structures to have similar taxonomic structures, suggesting that the patterns of guild and taxonomic variation are too complex to be ranked on a single scale. However, particularly large or small guilds on single tree species tended to contain at least one particularly large or small taxon as well, indicating that outsized guilds resulted from the presence of outsized taxa rather than a uniform swelling or shrinkage of all taxa in a guild. Most of this pattern occurred in the leaf-miners and gall-formers which appeared to be less saturated than the chewers and sap-feeders. Other than this, ''outsized'' taxa appeared idiosyncratically and unpredictably across all guilds, host trees and taxonomic groups. The large amount of unexplained guild variation in this system suggests that the stable predictable guild structures proposed for other faunas are not mirrored here. Instead, the linkage between outsized taxa and guilds suggests a strong historical component contributing to the functional structure in this fauna.