Functional web analysis: Detecting the structure of population dynamics from multi-species time series

The dynamics of animal populations are determined, to a greater or lesser extent, by interactions with other organisms in the ecological web within which they are embedded - what is called the functional web. I propose a methodology for determining the structure of the functional web from a series of observations on the densities of constituent populations made over time - a multi-species time series. The approach is based on analysis of the R-function for each species; i.e., the relationship between the per-capita rate of change of each Population and (1) the density of the population at different times in the past, providing clues to the order of population regulation, and (2) the densities of all potentially interacting species, providing clues to the inter-specific associations involved in population regulation. The application of the methodology is illustrated by application to a series of observations on Tengmalm's owls and three small mammals in Finland and, in a more cursory way, on spruce needleminers interacting with a guild of parasitoids in a Danish spruce plantation.