The relationship between corallite morphology and colony shape in some massive reef-corals

Multivariate statistical tests are performed on three coral species to determine if a relationship exists between colony shape and corallite morphology. Hemispherical to branched colony shapes are emphasized. The material consists of specimens of Montastraea annularis and M. cavernosa from modern reef habitats in Jamaica. Colonies of the more branched M. limbata from the Neogene of the Dominican Republic are analyzed for comparison. The characters studied consist largely of linear measurements of colony dimensions and corallite structures in transverse thin-sections. The results show that different complexes of corallite characters vary within each species. With the possible exception of a complex describing theca thickness in M. annularis, none of these corallite complexes is related to variation in colony shape within species. Colony shape variation within species is related to upward colony growth rate. These results indicate that corallite morphology and colony shape can be represented by two different vectors of variation within species. Comparisons of intraspecific with interspecific patterns suggest that a strong genetic component explains colony shape variation in corals.