Phylogenetics and morphological evolution of coral‐dwelling barnacles ( B alanomorpha: P yrgomatidae)

Pyrgomatid barnacles are a family of balanomorphs uniquely adapted to symbiosis on corals. The evolution of the coral‐dwelling barnacles is explored using a multi‐gene phylogeny ( COI , 16 S , 12 S , 18 S , and H 3) and phenotypic trait‐mapping. We found that the hydrocoral associate Wanella should be excluded, while some archaeobalanids in the genus Armatobalanus should be included in the P yrgomatidae. Three well supported clades were recovered: clade I is the largest group and is exclusively I ndo‐ W est P acific, clade II contains two plesiomorphic I ndo‐ W est P acific genera, while clade III is comprised of E ast and W est A tlantic taxa. Some genera did not form reciprocally monophyletic groups, while the genus Trevathana was found to be paraphyletic and to include members of three other apomorphic genera/tribes. The highly unusual coral‐parasitic hoekiines appear to be of recent origin and rapidly evolving from Trevathana sensu lato . Pyrgomatids include six‐, four‐, and one‐plated forms, and exhibit convergent evolutionary tendencies towards skeletal reduction and fusion, loss of cirral armature, and increased host specificity. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society , 2014, 113 , 162–179.