VARIATION OF TROPHIC FRACTIONS AND CONNECTANCE IN FOOD WEBS

Abstract

We present and illustrate methods of analyzing food web structure based on generalized linear models. Applied to the published food webs of Schoenly et al, these methods reveal strong associations of trophic fractions and connectance with the number of species in the web. Furthermore, the nature of these relationships depends on the habitat type of the web. Measures of goodness-of-fit of the statistical models reveal pronounced overdispersion, i.e., web-to-web variation in trophic fractions and connectance that greatly exceeds the variation attributable to the number of species and habitat type of the web. These results suggest it may be difficult to identify laws governing food web properties over a wide range of organisms and habitats.