Heritability for egg size in the serpulid polychaete Hydroides elegans

Many quantitative models on the evolution of divergent life histories in marine invertebrates have focused on egg size with little empirical support for the assumption that significant heritability for egg size is present. Narrow-sense heritability (h super(2)) is the proportion of total phenotypic variance in egg size that is made up of additive genetic variance, and is a predictor of short-term response to selection. We estimated h super(2) for the trait of egg size in the polychaete worm Hydroides elegans using artificial selection and by using a half-sibling breeding design. The cumulative realized heritability was calculated as 0.58 for egg size in a population of H. elegans in Pearl Harbor, Hawaii. Similarly, the half-sib breeding design gave an estimate for h super(2) of 0.45 for the same population. This indicates that there is substantial potential for egg size to respond to varying selective pressures, at least in the direction of increase.