Heterozygote advantage

At this point it's fairly clear that heterozygote advantage is not going to be a major force in the maintenance of genetic diversity simply because we've found so few examples. Perhaps not surprisingly with our rapidly expanding knowledge of genetics and gene function someone has now found some examples of heterozygote advantage that don't involve partial resistance to a disease. I missed this paper in PLoS ONE a few years ago:

Heterozygote Advantage for Fecundity
Heterozygote advantage, or overdominance, remains a popular and persuasive explanation for the maintenance of genetic variation in natural populations in the face of selection. However, despite being first proposed more than 80 years ago, there remain few examples that fit the criteria for heterozygote advantage, all of which are associated with disease resistance and are maintained only in the presence of disease or other gene-by-environment interaction. Here we report five new examples of heterozygote advantage, based around polymorphisms in the BMP15 and GDF9 genes that affect female fecundity in domesticated sheep and are not reliant on disease for their maintenance.