Incongruence between morphotypes and genetically delimited species in the coral genus Stylophora: phenotypic plasticity, morphological convergence, morphological stasis or interspecific hybridization?
1 Courant Research Center "Geobiology", University of Göttingen, Goldschmidtstraße 3, 37077 Göttingen, Germany
2 CEA-Institut de Génomique, GENOSCOPE, Centre National de Séquençage, 2 rue Gaston Crémieux, CP5706, 91057 Evry Cedex, France
3 UMR UPMC-CNRS-MNHN-IRD 7138, Département Systématique et Évolution, Muséum National d'Histoire Naturelle, Case Postale 26, 57 rue Cuvier, 75231 Paris Cedex 05, France
4 URBO, Department of Biology, University of Namur, Rue de Bruxelle 61, 5000 Namur, Belgium
5 UMR LOBP, Centre d'Océanologie de Marseille, Campus de Luminy, Case 901, 13288 Marseille Cedex 09, France
6 UMR LOBP, Centre IRD de Tahiti, BP 529, 98713 Papeete, French Polynesia
7 Br. Alfred Shields FSC Marine Station and Biology Department, De La Salle University, Manila 1004, Philippines
8 Sesoko Station, Tropical Biosphere Research Center, University of the Ryukyus, Okinawa 3422, Japan
9 UR COREUS, IRD, B.P. A5, 98848 Nouméa, New Caledonia
BMC Ecology 2011, 11:22 doi:10.1186/1472-6785-11-22Published: 4 October 2011
Morphological data suggest that, unlike most other groups of marine organisms, scleractinian corals of the genus Stylophora are more diverse in the western Indian Ocean and in the Red Sea than in the central Indo-Pacific. However, the morphology of corals is often a poor predictor of their actual biodiversity: hence, we conducted a genetic survey of Stylophora corals collected in Madagascar, Okinawa, the Philippines and New Caledonia in an attempt to find out the true number of species in these various locations.
A molecular phylogenetic analysis of the mitochondrial ORF and putative control region concurs with a haploweb analysis of nuclear ITS2 sequences in delimiting three species among our dataset: species A and B are found in Madagascar whereas species C occurs in Okinawa, the Philippines and New Caledonia. Comparison of ITS1 sequences from these three species with data available online suggests that species C is also found on the Great Barrier Reef, in Malaysia, in the South China Sea and in Taiwan, and that a distinct species D occurs in the Red Sea. Shallow-water morphs of species A correspond to the morphological description of Stylophora madagascarensis, species B presents the morphology of Stylophora mordax, whereas species C comprises various morphotypes including Stylophora pistillata and Stylophora mordax.
Genetic analysis of the coral genus Stylophora reveals species boundaries that are not congruent with morphological traits. Of the four hypotheses that may explain such discrepancy (phenotypic plasticity, morphological stasis, morphological convergence, and interspecific hybridization), the first two appear likely to play a role but the fourth one is rejected since mitochondrial and nuclear markers yield congruent species delimitations. The position of the root in our molecular phylogenies suggests that the center of origin of Stylophora is located in the western Indian Ocean, which probably explains why this genus presents a higher biodiversity in the westernmost part of its area of distribution than in the "Coral Triangle".