Figure 4.

Schematic showing the effect of increasing offspring size variability on the mean size of offspring that mothers produce. Panels show relationship between mean offspring size and maternal fitness (as indicated by the dotted curves) and distribution of offspring sizes that mothers produce (as indicated by the normal distributions). Relationship between mean offspring size and maternal fitness taken from Marshall et al. (2006). Predicted size distribution of eggs that mothers should produce in order to maximize their own fitness based on D. Marshall & L. Bussiere 2005, unpublished analyses. (a) Mothers produce only a small range of offspring sizes; hence, the mean offspring size they produce is close to both the minimum offspring size threshold for survival and the optimum offspring size for that environment (as indicated by the vertical dashed line). (b) Mothers produce a larger range of offspring sizes; hence, the mean offspring size they produce must be further from both the minimum size threshold for survival and the optimum offspring size.