Morphological diversity of the coral genus Pocillopora in Clipperton. Corals of the genus Pocillopora are common on nearly all tropical reefs except in the Caribbean. Their taxonomy is extremely confusing due to their extensive phenotypic plasticity, and clear-cut diagnostic morphological characters are missing for most currently defined species : hence, individuals that cannot be reliably identified are common. Clipperton Island is a very good and somewhat extreme example of this confusion, with different taxonomic experts having recognized successively three , one or two , three  and six  species among specimens collected around this atoll. We illustrate here a small sample of this morphological variation: from left to right and top to bottom, colony 05Clip026, colonies 05Clip052 (left side of the picture, green) and 05Clip053 (right side of the picture, brown), colony 05Clip045, colony 05Clip018, colony 05Clip019, colony 05Clip002. According to the results of the molecular analyses presented in this article, the colonies in the four first photographs belong to one species (Pocillopora sp. A) and the last two colonies belong to another (Pocillopora sp. B), a delineation far from obvious based on their morphology.
Flot et al. BMC Evolutionary Biology 2010 10:372 doi:10.1186/1471-2148-10-372