Rare corals are hybridising, says study

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Rare coral species are saving themselves from extinction by hybridising with other coral species, according to research published by Australian scientists in a recent issue of the journal PLoS ONE.

The study by Zoe Richards and coauthors focused on 14 rare and eight common coral species of the genus Acropora in the Indo-Pacific (for the purposes of the study, rare species are defined as those which have been recorded at less than 2.5% of sites for which data are available in the World Wide Acropora Database), for which the authors carried out a phylogenetic analysis using the highly polymorphic single-copy nuclear Pax-C 46/47 intron and the mitochondrial DNA (mtDNA) control region as markers.

The authors found that many of the rare coral species are polyphyletic for both Pax-C and mitochondrial phylogenies, which has been interpreted as evidence for interspecific hybridisation.

The authors conclude, he results presented here imply that a number of rare Indo-Pacific Acropora species are the products of recent hybridisation events, and highlight the significance of hybridisation in coral diversification. Whether these species have hybrid origins or have evolved and then hybridised in the absence of conspecific gametes remains to be elucidated.

In summary, although it has often been assumed that small populations have a decreased potential for adaptation, our analyses imply that some rare acroporid corals may actually have increased adaptive potential as a consequence of introgressive hybridisation, and therefore may be less vulnerable to extinction than has been assumed.

For more information, see the paper: Richards ZT, MJH van Oppen, CC Wallace, BL Willis and DJ Miller (2008) Some rare Indo-Pacific coral species are probable hybrids. PLoS ONE 3(9), e3240. doi:10.1371/journal.pone.0003240