Keystone Species are Influencers in Ecosystems

In the sixties, ecologist Robert Paine introduced the concept of keystone species, referring to certain species that exert a crucial influence on ecosystems. Their extinction can have far-reaching consequences for the survival of the entire system. Influencers can be compared to keystone species, as they play a pivotal role in maintaining the system’s integrity. These influencers are the ones that hold the network together and ensure its sustainability. It is thus natural to map the problem of identifying these species in the ecological network to the problem of percolation. Given the importance of mutualistic species interactions in community dynamics due to their stabilizing and positive effect, the strategy that emerges to identify keystone species in mutualistic ecosystems is the k-core. Monitoring the k-core of the network anticipates the tipping point of ecosystem collapse. In this chapter, we review theoretical frameworks to identify keystone species within theories of influencers and assess their importance for stability, resilience, and vulnerability, as well as early warning systems to anticipate catastrophic collapses of ecosystems.