Following the publication of this article, it has been brought to our attention that the Academic Editor Dr Sandberg and one of the authors were affiliated at the same institution.

In line with the PLOS ONE competing interests policy (http://www.plosone.org/st...), we consider this as a potential conflict of interest. Dr Sandberg was invited by PLOS ONE to act as Academic Editor for this manuscript and we acknowledge that the journal should not have approached him to handle this manuscript.

We have therefore asked the Academic Editor Yuntao Wu to carefully evaluate the peer review process of this article. Dr Wu has confirmed that he is satisfied that the peer review process and the decision for publication are adequate. We are therefore content that the review process was handled correctly by Dr Sandberg.