MORPHOLOGICAL AND MOLECULAR CHARACTERIZATION OF SPECIES OF THE GENUS CENTROCERAS (CERAMIACEAE, CERAMIALES), INCLUDING TWO NEW SPECIES1

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Abstract
Centroceras clavulatum (C. Agardh) Montagne is widely reported as being a prime example of a cosmopolitan red algal species. Instead, C. clavulatum is here determined as restricted to northern Chile, Peru, southern California, southern Australia, and New Zealand. Specimens identified using the current species concept for "C. clavulatum" fall into nine morphological groups that correspond to highly supported clades in phylogenetic analyses. Three of these clades correspond to the resurrected species Centroceras gasparrinii (Meneghini) Kützing, C. hyalacanthum Kützing, and C. micracanthum Kützing. Two others are recognized as new species: Centroceras rodmanii sp. nov. from southern Chile, which is characterized by hooked spines arranged in a whorl at the node, a spine or flattened gland cell cut off from the first cortical initials, and a single acropetal cortical cell issued from the second cortical initials; and C. tetrachotomum sp. nov. from South Africa, which has a tetrachotomous branching pattern, straight spines in a whorl, an acropetal cortical cell and a spine or a flattened gland cell cut off from the first cortical initials, and a two-celled acropetal filament cut off from the second cortical initials. Three additional species from South Africa are also recognized as distinct species. All phylogenetic analyses of the rbcL gene, LSU rDNA, and SSU rDNA were consistent with the vegetative and tetrasporangial morphological distinctions, thus supporting the resurrection of three species and the description of two new species.