A phylogenetic analysis of DNA sequence data revealed that the morphological Caulerpa
entities, previously reported as C. corynephora Montagne (or C. racemosa var. corynephora (Montagne)
Weber-van Bosse) and C. ashmeadii Harvey from mangrove channels on the Thai Andaman Sea coast,
are both representatives of C. macrodisca Decaisne. The analyzed Andaman Sea specimens formed
one of four subclades in a monophyletic C. macrodisca clade that was sister to C. megadisca Belton &
Gurgel. Ramuli arrangement of C. macrodisca from the Andaman Sea was mostly in opposite pairs and
sometimes distichous. The shape of the ramuli varied from almost cylindrical to clavate or turbinate.
No pyrenoid was observed. Caulerpa macrodisca with characteristic large peltate ramuli has only been
reported in Thailand from the Gulf of Thailand. Its identity was confirmed with DNA sequence data
from a herbarium specimen. It is recommended to refer to the three morphological C. macrodisca
entities as ecads; i.e., C. macrodisca ecad macrodisca, ecad corynephora, and ecad ashmeadii.
Keywords
ITS rDNA sequence, Macroalgae, Morphological plasticity, TufA gene