Colpomenia durvillei (Scytosiphonaceae, Phaeophyceae): its distribution and relationships with other elongate species of the genus

The taxonomic distinctiveness and distribution of the brown alga Colpomenia durvillei are debatable; the species was first described from central Chile. We analyzed mitochondrial cox 3 and plastid rbcL sequences from specimens collected in central Chile and Sonora, Mexico, in combination with morphological observations of specimens collected in Chile, Peru, and Mexico. Compared with other elongate species of the genus, C. durvillei is distinguished by erect, elongate thalli arising from a wide colpomenioid base, up to eight layers of cortical and medullary cells, and plurilocular sporangia with many layers (up to 18 locules). In all phylogenetic analyses of cox 3 and rbcL sequences, all elongate species of the genus formed a clade, in which C. durvillei was consistently distinct from congeners. Colpomenia bullosa was closely related to C. durvillei in our cox 3 analyses, and the clade containing these two species was closely related to Colpomenia phaeodactyla. This is the first report to confirm C. durvillei by molecular data and also the first report on the occurrence of the species in Sonora, Mexico. It had previously been misidentified as a variant of C. phaeodactyla on the Pacific coast of South America, and the name C. durvillei was misapplied to C. bullosa in New Zealand.