Mutualist-induced morphological changes enhance growth and survival of corals
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Species interactions can induce morphological changes in organisms that affect their subsequent growth and survival. In Moorea, French Polynesia, epibiotic gammaridean amphipods induce the formation of long, branch-like coral “fingers” on otherwise flat, encrusting, or plating Montipora coral colonies. The fingers form as corals encrust tubes built by the amphipods and lead to significant changes in colony morphology. This study examines the costs and benefits of this association to the amphipods and corals and demonstrates that the interaction is a mutualism. Amphipods gain protection from predators by living within corals, and corals benefit by enhanced growth and survival. Benefits to the coral arise through direct effects due to the amphipods’ presence as well as through benefits derived from the altered colony morphology. This study demonstrates that induced morphological plasticity can be a mechanism for facilitation, adding to our knowledge of the roles mutualism, and phenotypic plasticity play in ecology.
KeywordsCoral Growth Reef Crest Finger Length Lateral Growth Rate Sand Patch
We thank Tom Adam, Nichole Price, Keith Seydel, and Jennifer Gowan for assistance in the field, William Rice for advice on the statistical analysis, and Sally Holbrook, Russell Schmitt, Gretchen Hofmann, Robin Pelc, Tamar Goulet, and two anonymous reviewers for helpful discussions and comments on the manuscript. This research was supported by a U.S. National Science Foundation grant (OCE 04-17412) and gifts from the Worster family and the Gordon and Betty Moore Foundation. This work is a contribution of the Moorea Coral Reef Long Term Ecological Research site, a component of the National Science Foundation’s Long Term Ecological Research Program and was conducted at the UC Berkeley Richard B. Gump South Pacific Research Station.
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