Scientists in Hawaii have confirmed using molecular techniques that classifying corals based on morphology alone is a bad idea.
Publishing their results in the journal BMC Evolutionary Biology, Zac Forsman and coauthors studied finger corals (Porites), in which they used nuclear and mitochondrial markers to examine coral lineages and then correlated their results against traditional coral taxonomy using morphological characters.
The authors analysed sequences from 91 individual coral colonies and found in at least two lineages that corals assuming both branching and mounding forms were genetically indistinguishable.
At the same time, they also found specimens matching the description of 'Porites lutea' to belong to three genetically divergent groups (implying that they represent three different species).
The authors conclude: Since coral ecosystems are increasingly threatened, there is a need to characterize and understand coral species in terms of interbreeding groups as opposed to nominal morphological units.
Our approach shows that morphological characters previously thought capable of delineating species must be reexamined to accurately understand patterns of evolution, endemism, and biodiversity in reef-building coral.
Species definitions based solely on evolutionarily labile, polymorphic, or phenotypically plastic traits are likely to be misleading and confound attempts to identify, understand, and conserve coral biodiversity or to recognize its loss.
For more information, see the paper: Forsman, ZH, DJ Barshis, CL Hunter and RJ Toonen (2009) Shape-shifting corals: molecular markers show morphology is evolutionarily plastic in Porites. BMC Evolutionary Biology 9, 45, doi:10.1186/1471-2148-9-45