Fish community reassembly after a coral mass mortality: higher trophic groups are subject to increased rates of extinction

Since Gleason and Clements, our understanding of community dynamics has been influenced bytheories emphasising either dispersal or niche assembly as central to community structuring.Determining the relative importance of these processes in structuring real-world communitiesremains a challenge. We tracked reef fish community reassembly after a catastrophic coral mortalityin a relatively unfished archipelago. We revisited the stochastic model underlying MacArthurand Wilson’s Island Biogeography Theory, with a simple extension to account for trophic identity.Colonisation and extinction rates calculated from decadal presence-absence data based on (1)species neutrality, (2) trophic identity and (3) site-specificity were used to model post-disturbancereassembly, and compared with empirical observations. Results indicate that species neutralityholds within trophic guilds, and trophic identity significantly increases overall model performance.Strikingly, extinction rates increased clearly with trophic position, indicating that fish communitiesmay be inherently susceptible to trophic downgrading even without targeted fishing of toppredators.