Naked Stony Corals: Skeleton Loss in Scleractinia
Hexacorallia includes the Scleractinia, or stony corals, characterized by having an external calcareous skeleton made of aragonite, and the Corallimorpharia, or mushroom corals, that lack such a skeleton. Although each group has traditionally been considered monophyletic, some molecular phylogenetic analyses have challenged this, suggesting that skeletal features are evolutionarily plastic, and reviving notions that the scleractinian skeleton may be ephemeral and that the group itself may be polyphyletic. Nevertheless, the most comprehensive phylogenetic study of Hexacorallia supported scleractinian monophyly (REF), and so this remains controversial. In order to resolve this contentious issue, we sequenced the complete mitochondrial genome sequences of nine scleractinians and four corallimorpharians and performed phylogenetic analysis that also included three outgroups (an octocoral and two sea anemones). Our data provide the first strong evidence that Scleractinia is paraphyletic and that the Corallimorpharia is derived from within the group, from which we conclude that skeletal loss has occurred in the latter group secondarily. It is possible that a driving force in such skeletal loss could be the high levels of CO{sub 2} in the ocean during the mid-Cretaceous, which would have impacted aragonite solubility. We estimate from molecular divergence measures that the Corallimorpharia arose in the mid-Cretaceous, approximately 87 million years ago (Ma), supporting this view. These data also permit us to date the origin of Scleractinia to 265 Ma, narrowing the gap between the group's phylogenetic origin and its earliest fossil record.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director, Office of Science. Office of Biological andEnvironmental Research; National Science Foundation (NSF)
- DOE Contract Number:
- DE-AC02-05CH11231; NSF:OCE0313708
- OSTI ID:
- 889895
- Report Number(s):
- LBNL-59177; R&D Project: Y00064; BnR: 600305000; TRN: US200620%%76
- Journal Information:
- Proceedings of the National Academy of Sciences, Vol. 103, Issue 24; Related Information: Journal Publication Date: 06/13/2006
- Country of Publication:
- United States
- Language:
- English
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