Nature Communications 5: Article number: 4868 (2014); Published 10 September 2014; Updated 26 February 2015.

Two affiliations for Fyodor A. Kondrashov were omitted from this Article. The correct affiliations are given below:

Bioinformatics and Genomics Programme, Centre for Genomic Regulation (CRG) 88 Dr. Aiguader, 08003 Barcelona, Spain.

Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain.

Institució Catalana de Recerca i Estudis Avançats (ICREA), 23 Pg. Lluís Companys, 08010 Barcelona, Spain.