Present address: Department of Cell and Molecular Biology, University of California, Berkeley, CA 94720, USA.
Molecular evidence for the hybrid origin of species in the soft coral genus Alcyonium (Cnidaria: Anthozoa: Octocorallia)
Article first published online: 6 APR 2004
Volume 13, Issue 6, pages 1495–1505, June 2004
How to Cite
Mcfadden, C. S. and Hutchinson, M. B. (2004), Molecular evidence for the hybrid origin of species in the soft coral genus Alcyonium (Cnidaria: Anthozoa: Octocorallia). Molecular Ecology, 13: 1495–1505. doi: 10.1111/j.1365-294X.2004.02167.x
- Issue published online: 6 APR 2004
- Article first published online: 6 APR 2004
- Received 6 November 2003; revision received 4 February 2004; accepted 4 February 2004
- concerted evolution;
- hybrid speciation;
- reticulate evolution
Several recent studies have suggested that hybridization may play a previously unrecognized and important role in the evolution of corals. Our observations of polymorphic and recombinant sequences in the multicopy ribosomal internal transcribed spacer (ITS) region suggested the possible hybrid origin of two European soft coral species, Alcyonium hibernicum and Bellonella bocagei. To examine this possibility further we cloned and sequenced ITS-1 from multiple individuals and populations of these two species as well as two sympatric congeners, A. coralloides and A. sp. M2. Phylogenetic analyses separated the observed sequence variants into two distinct clades. All A. coralloides sequences belonged to clade A, while A. sp. M2 had only clade B sequences. A majority of A. hibernicum individuals, however, contained both clade A and B sequences that were identical to the predominant sequence variants found in A. coralloides and A. sp. M2, respectively. This pattern of additivity suggests that A. hibernicum originated from a hybrid cross between A. coralloides and A. sp. M2, a hypothesis that is supported by its unusual mode of reproduction (meiotic parthenogenesis). The predominant sequence variant found in B. bocagei was a unique, derived clade B sequence; in addition, however, most individuals of this species also had copies of a sequence identified as a recombinant between clade A and clade B sequence types. The presence of this recombinant sequence in the B. bocagei genome suggests that this species may also be the product of past hybridization events within the clade. Reticulate evolution may explain the failure of several previous studies to resolve the phylogeny of these four species.