We recently noticed an error in the code that rendered Figure 4. The error concerns the way in which the data for the two-dimensional plots Figure 4 are selected from the three-dimensional data-arrays plotted in Figure 3.

This error does not impact any of the statistical analyses or any of the conclusions of the paper, nor will Figure 4 change in any qualitative way. Quantitatively, however, the datapoints in the correct Figure 4 may shift a little bit with respect to the erroneous Figure 4.

We have notified PLoS of our mistake and send them a corrected Figure 4. They are currently processing our correction request so I assume that the corrected Figure will be available shortly. We apologise for any inconvenience our mistake may have caused.