Massachusetts Institute of Technology, United States
Understanding the factors modulating the composition of marine ecosystems is paramount for improving restoration and sustainability strategies in the face of global environmental change. Community composition is primarily shaped by species interactions that depend on both the behavioral and physiological responses of individual species to their environment and on evolutionary and co-evolutionary processes. The latter process is the result of past environmental conditions and subsequent selection on populations encoded in the current structure of species interactions of ecological communities, i.e., the so-called ecological memory.
In this project, we aim to identify the structural signatures of ecological memory in coral reef fish communities that have experienced coral bleaching events. We use a global coral reef-fish database containing 3,464 sampling sites around the planet with 3,086 non-benthic marine species combined with a global coral bleaching database containing 12,000 coral sampling sites. We develop a bootstrap methodology to infer species interactions from species abundance data assuming generalized Lotka-Volterra dynamics. We measure the presence of ecological memory in coral reef fish communities by comparing the structure of species interactions across sites as a function of the occurrence and distance to coral bleaching events.
We identified a group of highly conserved and a group of highly variable species interactions across sites. Importantly, the group of highly conserved species interactions decreased gradually among sites that experienced more coral bleaching events or were in closer proximity to bleaching sites. In these post-bleaching sites, a new species group emerged suggesting the reshaping of community memory. These results indicate a trade-off between resilience and efficiency in the community structure, which is in line with previous empirical observations in coral reefs, where coral species became more resilient once they have experienced a heat shock. These findings give support to the existence of a structural signature (core of species interactions) characterizing the ecological memory of fish communities and the impact that extreme events may have on disrupting such memory.