Rare coral species may be saving themselves from extinction by hybridising with other coral species, says Australian scientist Zoe Richards. Richards and his colleagues have studied 14 rare[1] and eight common coral species of the genus Acropora in the Indo-Pacific.

In order to find out more about hybridisation among corals, the team did 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 analysis showed that many of the rare species are polyphyletic for both Pax-C and mitochondrial phylogenies, and this is seen as a clear sign of interspecific hybridisation.

The results of the study “Some rare Indo-Pacific coral species are probable hybrids” by Richards, Oppen, Wallace, Willis and Miller were published in a recent issue of the journal PLoS ONE[2].

In their paper, the authors explain how “[t]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.”

[1] For the purposes of this study, rare species were 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.

[2] 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