Studies of species interactions on coral reefs have primarily focused on fishes and corals that live conspicuously on the surface of the reef. However, the majority of the reef’s diversity comes from invertebrates and fishes that live embedded within the interstitial spaces of the reef, and we know little about the processes underlying the structure and stability of these more cryptic species. For example, a key group of fishes and decapods live embedded in the reef building coral Pocillopora. Many of these cryptic inhabitants are known coral mutualists that subsidize nutrients, clean the coral of sedimentation, and defend the coral from the predatory seastars. Our previous studies in this system suggest substantial context dependency degree of services provided by certain mutualists and that protective services vary with mutualist abundance. However, the processes that drive the structure and diversity of mutualist communities remain poorly understood. Here we experimentally test the hypothesis that predation promotes the diversity of mutualist reef cryptofauna. Here, we quantify the independent and combined effects of two predatory fishes on the abundance, diversity and composition of a diverse, but cryptic, coral reef fish and decapod community. We find strong effects of both predator density and identity on the abundance, diversity, and composition of fish and decapod communities. Predators substantially altered the dynamics of coral-dwelling decapods (a poorly studied but extraordinarily beautiful and diverse guild. Our results suggest that predation on mutualist communities may have negative indirect effects on host coral’s ability to withstand increasing frequency and intensity of natural and anthropogenic stressors on coral reefs.

This manuscripts is the newest in a series of studies that have examined the ecology of key mutualistic reef cryptofauna. Please check out our other papers that feature this same guild of symbionts.

Stier A.C.=, M.A. Gil=, C.S. McKeon=, S. Lemer‡, M. Leray‡, S.C. Mills‡, and C.W. Osenberg. 2012. Housekeeping mutualisms: do more symbionts facilitate host performance. PLoS ONE. 7(4): e32079PDF

McKeon C.S., Stier A.C., Boyer S.E.*, and Bolker BM. 2012.  Multiple Defender Effects: Synergistic coral defense by exosymbiotic crustaceans. Oecologia. 169:1095-1103. PDF

Stier A.C., McKeon C.S., Osenberg C.W. and J.S. Shima. 2010. Guard Crabs Alleviate Deleterious Effects of Vermetid Snails on a Branching Coral. Coral Reefs. 29 (4) 1019 – 1022. PDF

This paper is equally coauthored by: Adrian Stier (me) (University of British Columbia) and Matthieu Leray (Smithsonian Institution). Download the paper here or e-mail me ( for a copy of the manuscript.


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Adrian Stier

Ocean Tipping Points