Priority effects in coral reef fish communities of the Great Barrier Reef

Abstract

Priority effects occur when established residents influence the colonization of individuals entering the community and thus provide insight into mechanisms underlying spatial differences and temporal changes in community composition. Using 20 spatially isolated patch reefs, I factorially manipulated the presence and absence of resident predators (groupers and dottybacks) and potential competitors (damselfishes) to determine whether and how they affect subsequent recruitment and mortality of newly settled fishes. During the 50-day experiment at Lizard Island (Great Barrier Reef, western Pacific), prior residency by predators dramatically reduced recruitment of damselfish, surgeonfish, butterflyfish, and rabbitfish and increased damselfish recruit mortality. In contrast, prior residency by potential competitors only reduced recruitment of damselfish and rabbitfish and did not affect recruit mortality. Effects of competitors were likely due to aggressive interactions between competitors and recruits that increased susceptibility of recruits to predators. Effects of residents were strongest within 48 hours of settlement, resulting in rapid establishment of patterns that persisted to the conclusion of the experiment. These results are similar to those from a comparable experiment in the Bahamas (western Atlantic), suggesting that priority effects may be a generally important cause of temporal and spatial variability in the composition of reef fish communities.