Alcyonium Linnaeus. Two 1758, sensu stricto

Alcyonium Linnaeus, 1758

As discussed by McFadden & Ofwegen (2013), over time Alcyonium has become a repository for species of Alcyoniidae that lack the diagnostic characters of other genera, and the definition of the genus has expanded to encompass a broad range of colony growth morphologies and sclerite types. Phylogenetic analyses suggest that Alcyonium sensu stricto is restricted to species that have sclerites arranged as a collaret and points in the polyps and two distinct layers in the coenenchyme: a surface layer of predominantly radiates and clubs and an interior layer of spindles or rods. In addition, the sclerites are often brightly colored and retain their color in alcohol. Of the many South African species that have been assigned to this genus, only five share the sclerite characteristics of Alcyonium sensu stricto. They differ from all other members of the genus in their colony growth form, however, which is typically unbranched and clavate or capitate with a clearly demarcated stalk and polyparium. Phylogenetic analyses of the two South African Alcyonium species for which there are DNA sequence data place them in a distinct clade that is sister to a clade of North Atlantic and Mediterranean species (Fig. 1).