Resource-allocation rules and the heritability of traits.

I hypothesize that the heritability of a trait, and thus its evolutionary responsiveness to natural selection, should be positively related to the priority with which resources are allocated to that trait. Low-priority traits are more sensitive to environmental effects, thus reducing the relative effect of genetic differences on phenotypic variation of these traits. This allocation-priority hypothesis explains why life-history traits, such as those involving growth and reproduction, generally have lower heritabilities than higher-priority morphological and physiological traits related to body maintenance. This hypothesis also shows how an organism-centered approach, as used in physiological ecology, can contribute to the development of evolutionary theory.