Structural constraints on novel ecosystems in agriculture: The rapid emergence of stereotypic modules

• Agricultural systems are novel ecosystems and frequently include exotic species.
• Natural and novel ecosystems are structured in a non-random fashion, with certain rules of organization that represent repeated modules of organization.
• Our understanding of basic aagroecosystem dynamics is informed by framing them as composed of three basic modularities:.(1)the trophic level/food web module;(2)predators and diseases in space and time;(3)trait-mediated cascades.
• The extent to which these ecological modules suffice to understand the dynamics of agroecosystems, is unknown, and thus presents an exciting research agenda.

Agricultural ecosystems are, by their very nature, a cauldron of novel ecosystems, emerging with exotic species at the core of their very existence and followed by invasions of other species, so-called associated biodiversity. Within that framework similar ecosystem modules become assembled very rapidly with native and non-native species, a consistency that reflects deep ecological principles at both local and landscape levels. Here we describe three such modules: trophic levels and food webs, natural enemies in space and time, and trait-mediated trophic cascades and the accumulation of non-linearities. We propose that diverse agroecosystems are bound to contain such modularities and therefore have similar ecological structures as natural systems in spite of their novelty. We use examples from the coffee agroecosystem in Mexico to illustrate these modules.