Development of the extant diversity in Halimeda is linked to vicariant events

Partial 18S rDNA sequences, including a 102 base pair insertion, were used to infer a phylogeny among 48 samples across all sections in Halimeda Lamou roux, 1812. The phylogeny reveals a separation of the monophyletic section Rhipsalis into a western Atlantic and a western Pacific clade. Consequently , morphologically similar species within this section such as H. monile (El lis & Solander) Lamouroux (western Atlantic), and H. cylindracea Decaisne ( western Pacific), are not sister taxa. Vicariant events that separated the tropical regions of the Atlantic and Indo-Pacific Oceans can explain the ob served biogeographical pattern in section Rhipsalis.