Morphological characterization of lineages within the calcified tropical seaweed genus Halimeda (Bryopsidales, Chlorophyta)

Abstract

Halimeda Lamouroux constitutes a genus of calcified and segmented green seaweeds within the Bryopsidales. Molecular phylogenetic assessments have uncovered five principal monophyletic lineages within the genus. In the present study we define these lineages morphologically. We gathered morphological data from specimens used in the molecular analyses as well as from collections having a similar morphology and originating from the same geographical region. Starting from the lineages and their morphological synapomorphies, we define and illustrate five natural sections within Halimeda. All or most medullary siphons traversing the nodes between segments fuse into a single unit in specimens of lin..