Molecular phylogenetic analyses of shallow-water Caribbean octocorals

Abstract

Octocorals, especially gorgonians, are conspicuous on Caribbean coral reefs, but there is no consensus regarding species relationships. Mitochondrial protein-coding genes [NADH-dehydrogenase subunits 2 (ND2) and 6 (ND6), and mutS homolog (msh1), 1633 bp] from 28 shallow-water species were sequenced to develop the first molecular phylogeny for Caribbean octocorals. The specimens were collected primarily in the Caribbean or off Brazil in 1999-2001. Morphological characters (sclerites and axial ultrastructure) were also examined in order to map them onto the molecular phylogeny. Analyses of both nucleotide and amino acid substitutions using maximum parsimony and likelihood (including maximum-likelihood and Bayesian analysis) generated very similar results, with most nodes having high levels of support. These molecular results were significantly different from the generally accepted classification. Neither Plexauridae nor Gorgoniidae were monophyletic. Plexaurella spp., nominal plexaurids, were basal to the gorgoniids, sharing many morphological characters with them. This corroborates previous findings using secondary metabolites and biosynthetic pathways. The sea fans, Gorgonia spp. and Pacifigorgia spp., as well as the pinnate gorgonians, Muriceopsis flavida and Pseudopterogorgia spp., did not have sea fan or pinnate relatives, suggesting there has been convergent evolution of colony form. Caribbean plexaurids appeared more derived and/or recently evolved according to both morphological and molecular data (e.g. Eunicea spp. and Plexaura spp.). Molecular phylogenetics is a promising approach for reconstructing phylogenetic relationships among octocorals as well as to understand their complex morphology. Electronic Supplementary Material is available if you access this article at http://dx.doi.org/10.1007/s00227-003-1018-7. On that page (frame on the left side), a link takes you directly to the supplementary material. IntroductionOctocorals, sessile cnidarians, are found in marine habitats ranging from intertidal to abyssal waters and are distributed from the Arctic to the Antarctic (Bayer 1961). Gorgonians, octocorals containing a sclero-proteinaceous axis, are ecologically important and the dominant macrofauna on many Caribbean reefs. There can be up to 40 octocoral species on a single Caribbean coral reef (Sa´nchez et al. 1997 Sa´nchez 1999), and octocoral communities produce dense and colorful gardens, which provide three-dimensional structures for many reef dwellers and scenic value for underwater activities (Fig. 1). Despite their importance, evolutionary relationships among Caribbean octocorals have received Marine Biology (2003) 142: 975-987

Patterns of morphological integration in marine modular organisms: supra-module organization in branching octocoral colonies

“…Resolved phylogenetic relationships and species phylogenetic distances for the comparative analyses were reconstructed from coding mitochondrial DNA (mtDNA) sequences (Sánchez et al 2003b; see also figure 3 and electronic Appendix A, available on The Royal Society's Publications Web site). For continuous quantitative traits, the method of independent contrasts (Felsenstein 1985(Felsenstein , 1988, using species means, was applied to each parameter using the Contrast routine in Phylip v. 3.6 (Felsenstein 1989).…”

Review and five new Alaskan species of the deep‐water octocoralNarella(Octocorallia: Primnoidae)

“…msh1 has been shown to be more variable in octocorals than are COI and 16S (France & Hoover, 2002) and both msh1 and NADH subunits are currently used in octocoral phylogenetics (e.g. France & Hoover 2001;Sanchez et al, 2003;McFadden et al, 2006, Wirshing et al, 2005.…”

“…For PCR amplification, primers were used from Sanchez et al (2003). ND6-1487F and ND3-2126R were used for ND6 and ND42599F and Mut3458R were used to amplify the 5' end of msh1.…”

“…Parker & Tunnicliffe, 1994;Rogers, 1994;DeForges et al, 2000), and these three species may represent a relatively recent radiation of Narella on Derickson Seamount. Sanchez et al (2003) point out that these genes may provide limited resolution for recently evolved species, however, it is also likely that msh1 and ND6 simply have too low variation levels to distinguish all species within this genus. Five species in the octocoral genus Corallium (Family Coralliidae), showed no sequence variation in the first 100 bp of the msh1 gene (France & Hoover, 2002).…”

“…Two species of Hawaiian Narella differed by 2.8% in the same 100 bp region of msh1 (France & Hoover, 2002). Other published data on this region of the msh1 with multiple species in a single genus include those of Sanchez et al (2003) and Wirshing et al (2005) Table 4 Uncorrected 'p' pairwise distances (%) for new species of Narella, based on ND6 sequences.…”