Species richness and resource availability: a phylogenetic analysis of insects associated with trees.
The data on the number of species of insects associated with various trees in Britain have been reanalyzed to factor out possible bias from phylogenetic effects. It was found that tree availability (range and abundance) continues to provide a good predictor (r = 0. 852) of insect-species richness, slightly better than straightforward cross-species analyses. Of the two components of tree availability, tree abundance gives a much better prediction than tree range. The species richness on trees of major taxa with similar trophic habits (Lepidoptera and Hymenoptera/Symphyta and the two suborders of the Homoptera-Auchenorrhyncha and Sternorrhyncha) shows positive correlations; there is thus no evidence of competitive exclusion at this taxonomic level.
Kelly
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Department of Zoology, University of Oxford, Oxford OX1 3PS, United Kingdom.
Southwood
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TR