Figure 1. Proportion of (a) normally, (b) abnormally, and (c) total (=normally+abnormally) fertilized eggs as function of sperm concentration in mussels collected from high (H) and low (L) population density and mated in a fully factorial fertilisation design. For each experimental block, four females were paired with four males (andvice versa ) at six different sperm concentrations. Each line within a panel represent the mean of a specific male and female population density. Hence, comparing the red vs blue lines shows the difference between H and L females. Comparing squared vs circles shows the differences between H and L males.