31 research outputs found
Mitochondrial and nuclear genes suggest that stony corals are monophyletic but most families of stony corals are not (Order Scleractinia, Class Anthozoa, Phylum Cnidaria)
Get PDFModern hard corals (Class Hexacorallia; Order Scleractinia) are widely studied because of their fundamental role in reef
building and their superb fossil record extending back to the Triassic. Nevertheless, interpretations of their evolutionary
relationships have been in flux for over a decade. Recent analyses undermine the legitimacy of traditional suborders,
families and genera, and suggest that a non-skeletal sister clade (Order Corallimorpharia) might be imbedded within the
stony corals. However, these studies either sampled a relatively limited array of taxa or assembled trees from heterogeneous
data sets. Here we provide a more comprehensive analysis of Scleractinia (127 species, 75 genera, 17 families) and various
outgroups, based on two mitochondrial genes (cytochrome oxidase I, cytochrome b), with analyses of nuclear genes (Ăźtubulin,
ribosomal DNA) of a subset of taxa to test unexpected relationships. Eleven of 16 families were found to be
polyphyletic. Strikingly, over one third of all families as conventionally defined contain representatives from the highly
divergent "robust" and "complex" clades. However, the recent suggestion that corallimorpharians are true corals that have
lost their skeletons was not upheld. Relationships were supported not only by mitochondrial and nuclear genes, but also
often by morphological characters which had been ignored or never noted previously. The concordance of molecular
characters and more carefully examined morphological characters suggests a future of greater taxonomic stability, as well as
the potential to trace the evolutionary history of this ecologically important group using fossils
A Comprehensive Phylogenetic Analysis of the Scleractinia (Cnidaria, Anthozoa) Based on Mitochondrial CO1 Sequence Data
Get PDFClassical morphological taxonomy places the approximately 1400 recognized species of Scleractinia (hard corals) into 27 families, but many aspects of coral evolution remain unclear despite the application of molecular phylogenetic methods. In part, this may be a consequence of such studies focusing on the reef-building (shallow water and zooxanthellate) Scleractinia, and largely ignoring the large number of deep-sea species. To better understand broad patterns of coral evolution, we generated molecular data for a broad and representative range of deep sea scleractinians collected off New Caledonia and Australia during the last decade, and conducted the most comprehensive molecular phylogenetic analysis to date of the order Scleractinia.Partial (595 bp) sequences of the mitochondrial cytochrome oxidase subunit 1 (CO1) gene were determined for 65 deep-sea (azooxanthellate) scleractinians and 11 shallow-water species. These new data were aligned with 158 published sequences, generating a 234 taxon dataset representing 25 of the 27 currently recognized scleractinian families.There was a striking discrepancy between the taxonomic validity of coral families consisting predominantly of deep-sea or shallow-water species. Most families composed predominantly of deep-sea azooxanthellate species were monophyletic in both maximum likelihood and Bayesian analyses but, by contrast (and consistent with previous studies), most families composed predominantly of shallow-water zooxanthellate taxa were polyphyletic, although Acroporidae, Poritidae, Pocilloporidae, and Fungiidae were exceptions to this general pattern. One factor contributing to this inconsistency may be the greater environmental stability of deep-sea environments, effectively removing taxonomic "noise" contributed by phenotypic plasticity. Our phylogenetic analyses imply that the most basal extant scleractinians are azooxanthellate solitary corals from deep-water, their divergence predating that of the robust and complex corals. Deep-sea corals are likely to be critical to understanding anthozoan evolution and the origins of the Scleractinia
