Nature Communications 5: Article number: 5586 (2014); Published: 24 November 2014; Updated: 27 January 2015

In this Article, there are errors in the labelling of the x axis in Fig. 2b. The labels ‘20’, ‘40’, ‘60’ and ‘80’ should have been ‘200’, ‘400', ‘600' and ‘800’, respectively. The correct version of this figure appears below.