Nature Communications 5: Article number: 3512 (2014); Published: 24 March 2014; Updated: 18 September 2014.

There were errors associated with the Supplementary Data in the version of this Article originally published, which were introduced while the HTML was being prepared. The titles of Supplementary Data 8, 9, 10, 11, 12 and 13 were incorrectly linked to Supplementary Data 7, 8, 9, 10, 11 and 12, respectively, and the file for Supplementary Data 13 was omitted. These errors have now been corrected in the HTML version of the Article; the PDF was correct from the time of publication.