Whilst much attention has been paid to direct biotic interactions between plants and animals, this chapter shows that important interactions may be mediated by way of plant or animal effects on the environment. We term these complex interactions ‘resource webs’, in which each trophic level can influence the availability of basic resources, which in turn can affect other organisms. The concept is illustrated with a number of examples drawn primarily from studies of the effects of gopher and ant activities in annual grasslands found on serpentine in California and other regions of Mediterranean-type climate. The existence of environment-mediated interactions indicates that plant-animal relationships are important not only at the population level but also at the level of ecosystems as well.
