VARIATION OF TROPHIC FRACTIONS AND CONNECTANCE IN FOOD WEBS

We present and illustrate methods of analyzing food web structure base d on generalized linear models. Applied to the published food webs of Schoenly et al., these methods reveal strong associations of trophic f ractions and connectance with the number of species in the web. Furthe rmore, the nature of these relationships depends on the habitat type o f the web. Measures of goodness-of-fit of the statistical models revea l pronounced overdispersion, i.e., web-to-web variation in trophic fra ctions and connectance that greatly exceeds the variation attributable to the number of species and habitat type of the web. These results s uggest it may be difficult to identify laws governing food web propert ies over a wide range of organisms and habitats.