Static, Ontogenetic, and Evolutionary Allometry: A Multivariate Comparison in Nine Species of Water Striders

Static, ontogenetic, and evolutionary allometry in all five larval instars of nine species of the water strider genera Gerris and Aquarius were compared using a multivariate approach. Common principal component analysis (CPCA), a generalization extending principal component analysis (PCA) to multigroup situations, was carried out on covariance matrices of log-transformed measurements of eight characters of antennae and legs. For all three types of allometry, a good fit of the model of simple multivariate allometry was found, and PCA results were similar in all instars and species, which justifies the use of CPCA to estimate a common pattern of allometric variation for each of the three types of allometry. We found a fairly close association between static and ontogenetic allometry, which indicates at least in part a developmental origin of individual variation. Evolutionary allometry differed markedly from static and ontogenetic allometry, with leg segments displaying strongly positive allometry. We discuss the possible importance of differences in habitat use for the evolution of the characters considered. Static, ontogenetic, and evolutionary variation are reciprocally interrelated phenomena that need to be considered in studies of the evolution of morphological traits.