Resource‐driven terrestrial interaction webs

Terrestrial food webs based on living plants may well represent 75% of global terrestrial biodiversity. The majority of component species are specialists and a large proportion is parasitic as herbivores and carnivores, with consequences for high sensitivity to heterogeneity on a variety of scales. Relatively large primary producers support relatively small insect herbivores and carnivores, with plants providing both food and habitat, making resource‐driven effects very strong. Complexity of resources provided by plants, with influences up the food web, is generated by at least seven major factors: (i) plants as food; (ii) plants as habitat; (iii) the physical traits of plants such as size, toughness and trichomes; (iv) traits of plants that require evolutionary responses by herbivores in terms of crypsis, phenological synchrony, life history and behavioral adaptations; (v) the constitutive chemicals in plants; (vi) the induced changes in plants caused by herbivory; and (vii) landscape and biogeographic variation in vegetation types and food web richness. No other trophic level has such a wide‐ranging impact on other trophic levels. But such broad impact makes the term ‘food web’ overly narrow and inadequate. The term ‘interaction web’ is preferable, aiding recognition of the many kinds of interactions that pass up food webs from living plants. Any claim that top‐down impact is stronger than bottom‐up influences is necessarily couched in a narrow sense of biomass or numbers reduction.