A phylogenetic study of chthamaloids (Cirripedia; Thorcica; Chthamaloidae) based on 16S rDNA and COI sequence analysis

Abstract

The sequences of gene fragments encoding cytochrome c oxidase subunit I (COI) and 16S rDNA were obtained and used to construct phylograms of eight taxa of chthamaloid barnacles using the scalpelloid Calantica as an out-group. The phylograms support the basal position of Catomerus within the chthamaloids. Analysis of 16S rDNA shows that Octomeris and the four-plated barnacle Chamaesipho are located on the same clade, while Chthamalus, Euraphia and Tetrachthamalus are located on a second clade, indicating that reduction in the number of shell plates occurred twice in the evolution of the chthamaloids. The topology of phylograms based on COI sequences is poorly resolved: 93% of third position nucleotides in this fragment are polymorphic while the amino acid sequences are strictly conserved. We assume that in the chthamaloids, at least at the generic level, polymorphism in the COI gene is saturated beyond phylogenetic information and cannot resolve the phylogenetic relationships within this superfamily. © 2004 The Linnean Society of London.