Fig. 5

The evolution of gMR in the absence of positive selection for body mass and SMP. The SMP’s Som parameter was fixed at 0.34 (red), 0.24 (green; enhanced 10X) and 0.2 (blue; enhanced 40X); a linear decrease in the Som value results in a substantially improved SMP, so that the green SMP is ~10X more efficient compared to red, and the blue is a ~4X more efficient SMP than the green. The standard (red) SMP leads to a significantly stronger selection for lower gMR (non-overlapping 95% CIs); however, the absence of difference between the 10X (green) and 40X (blue) improved SMPs indicates that overly improved SMPs might not provide any further difference for how selection acts on gMR. Note also that even with enhanced SMP (green and blue) there is significant decrease (non-overlapping 95% CIs) in gMR relative to either the initial gMR or to the gMR at the peak (resulting from selection to optimize other traits)