A successional shift enhances stability in ant symbiont communities

Throughout succession, communities undergo structural shifts, which can alter the relative abundances of species and how they interact. It is frequently asserted that these alterations beget stability, i.e. that succession selects for communities better able to resist perturbations. Yet, whether and how alterations of network structure affects stability during succession in complex communities is rarely studied in natural ecosystems. Here, we explore how network attributes influence stability of different successional stages of a natural network: symbiotic arthropod communities forming food webs inside red wood ant nests. We conducted extensive field sampling to compare the composition of the symbiont community across 51 host nests of varying age, representing different succession stages. We recorded abundance of 16 functional groups of symbionts spanning different specialization and trophic levels. Joint species distribution modelling indicated nest age as the driver of the compositional shifts: symbiont communities in old nests contained a greater proportion of specialists and more even species abundance distributions. We then reconstructed community matrices and showed that this enhanced evenness lead to an augmented food web stability of the symbiont communities in older nests. Overall, this study demonstrates that succession begets stability in a natural ecological network by making the community more even.