Frozen Evolution. Or, that’s not the way it is, Mr. Darwin. A Farewell to Selfish Gene.

The individual species differ in the width of their ecological valence.Eurytopic speciesare capable of utilizing a wider range of resources and successfully surviving in various types of habitats; in contrast, stenotopic species specialize on a narrow range of resources and are capable of surviving only in a narrow range of conditions.Comparative studies have shown that stenotopic species have a far greater tendency to become extinct than eurytopic species (Purvis, Jones, & Mace 2000).This is undoubtedly a result of the fact that eurytopic species are capable, when necessary, of reorienting themselves to a different type of resource, are capable of tolerating quite drastic climatic changes and generally occur over a broader area than stenotopic species.As will be mentioned below (XXII.6.3), the size of the geographic range tends to be the decisive factor from the viewpoint of survival of the species.