Size and Shape of Sawfly Assemblages on Arroyo Willow

We present new techniques for the analysis of abundance data from multispecies communities. We partitioned variation in abundance into two components: variation in absolute abundance and variation in relative abundance. We examined patterns of absolute and relative abundance for multispecies assemblages from a multivariate morphometrics perspective. Multivariate morphometric analyses of abundance patterns have both heuristic and quantitative advantages over information theoretic approaches. We extended the concepts of isometry and allometry to community structure and illustrated these principles with density data from a group of five closely related tenthredinid sawflies that infest clones of arroyo willow (Salix lasiolepis). There were significant differences among willow clones in the size and shape of their sawfly assemblages. In fact, willow clones are virtually unique in terms of absolute and relative densities of sawflies. We used size and shape analysis to compare community structure of sawflies on male and female willows. Male clones differed from female clones in absolute densities of sawflies but not in relative densities.