When morphology cannot identify species: high morphological diversity of Pocillopora corals (Anthozoa: Scleractinia) in the Eastern Tropical Pacific

Accurate species identification is fundamental to biological diversity assessments and critical for understanding ecological and evolutionary dynamics. Nonetheless, the high levels of morphological variation in many scleractinian corals have blurred the recognition of species boundaries. The genus Pocillopora is widely distributed and exhibits high levels of colony level phenotypic plasticity and polymorphism, leading to the description of over 40 species worldwide. In the Eastern Tropical Pacific (ETP), nine “morphospecies” have been recorded, but only four genetically distinct species are now recognized in the area, based initially on variation in mitochondrial DNA and then supported by genomic data. This study aimed to identify useful molecular and morphological traits to recognize and describe the Pocillopora diversity in the ETP. We found that Histone and mitochondrial markers could identify discrete lineages, while most of the nuclear genes analyzed offered little power for delineation. Neither colonial morphology nor corallite micro-morphology reliably corresponded to the lineages identified. Based on mitochondrial and nuclear genetic data, we found that at least four distinct lineages occur in the ETP. The species names associated with these mitochondrial haplotypes in other studies are most often P. cf. effusa , P. lacera , and two putative cryptic species: P. capitata and P. meandrina .