Morphological polymorphism of Desmophyllum dianthus (Anthozoa: Hexacorallia) over a wide ecological and biogeographic range: stability in deep habitats?

Abstract

Although zooxanthellate corals are well known for their ecophenotypic variations, there is increasing evidence that azooxanthellate species also harbour a high degree of plasticity. Desmophyllum dianthus, a widespread solitary coral, exhibits a high degree of morphological variation in corallum forms that has never been analysed quantitatively. To assess if the clear morphological variation of D. dianthus follows a specific pattern based on environmental (or others) variables, this study combines three different morphometric approaches: (1) classical linear external morphology, (2) use of three-dimensional coordinates landmarks, and (3) linear measurements and counts made of cnidocyst features. Comparative morphological characterization of D. dianthus specimens shows a pattern of intraspecific variation over a wide ecological and biogeographic range. However, additional future studies on this and other proposed cosmopolitan species, including a similar sampling effort in localities and specimens, will be useful to explore the existence of common global patterns of morphological variability. Hypotheses for intraspecific polymorphism are discussed to explain the incongruence between the obtained results and the seemingly high morphological variability observed within D. dianthus.