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

Abstract

Partial 18S rDNA sequences, including a 102 base pair insertion, were used to infer a phylogeny among 48 samples across all sections in Halimeda Lamouroux, 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 (Ellis and 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 observed biogeographical pattern in section Rhipsalis.