The publishers apologise for the incorporation of three errors, introduced during revisal of galley proofs for the above paper. The concentration of PCR primers used per reaction should read 500 nM each. All references to a gel figure removed during final editing should be deleted, including the phrases 'as is clearly evident', and '(lane 1)'. On the basis of his significant contributions, Marcos P. Rivas should have been listed as second author as is shown above. © 1995 Oxford University Press.