1. Survival and reproduction in different habitats of a heterogeneous environment are affected by intrinsic habitat properties as well as by habitat-independent extrinsic factors. It is argued that the ranking of habitats according to quality may depend on extrinsic environmental factors that act with the same intensity in all habitats. This can happen if, across habitats, high reproductive success in the absence of extrinsic mortality is coupled with late reproduction.
2. In a model of a semelparous organism with overlapping generations that uses two habitats, the effect of different patterns of extrinsic mortality on habitat quality are analysed, as measured by the reproductive: value of an egg, which estimates its expected contribution to the future gene pool.
3. Measurements of fitness components in Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) on four host species demonstrate that, across hosts, long development can be associated with high reproductive success in the absence of extrinsic mortality. As a result, the quality ranking of three out of the four hosts would be different in a stable population regulated by intraspecific competition and egg parasitoids than in a growing population or a stable population regulated by age-independent larval mortality.
4. It is suggested that habitat-independent mortality may play a role in the evolution of ecological niches.