In chemical ecology, keystone compounds are chemical substances produced by organisms that play a crucial role in mediating ecological interactions within an ecosystem. These compounds can influence behaviors, interactions, and the overall dynamics of communities. Keystone compounds can have cascading effects throughout an ecosystem, affecting not only the organisms directly interacting with them but also other species within the ecosystem. By understanding the roles of these compounds, ecologists can gain insights into the complex web of interactions that shape ecological communities.
The forb, Solidago altissima (Asteraceae), dominates Eastern North American old-field communities. Within these communities, insect herbivory is a major mediator of competition between plant species and maintains high plant species diversity. Solidago altissima roots produces high amounts of polyacetylene that are major allelopathic compounds but also affect soil microbial communities. The interaction between polyacetylenes, soil microbial communities and herbivory affect the outcome of competitive interactions between plants within the early succession plant communities and so determine plant community composition. Thereby polyacetylenes play a crucial role that goes for beyond its allelopathic function and thus represents one of the very few cases of keystone compounds in terrestrial systems. Here we present evidence for this keystone compound function and identify plant secondary metabolism as a major driver of plant community composition.