Correction to: Nature Communications (2017) https://doi.org/10.1038/s41467-018-02978-7; Article published online: 08 Feb 2018

The original version of this Article omitted an acknowledgement to the source of Fig. 1a. The following has been added to the end of the caption to Fig. 1:

‘Figure 1a adapted from ref. 13 (copyright 2016 Macmillan Publishers)’.

This has been corrected in the PDF and HTML versions of the Article.