XXII.6.1 Species with a broader ecological valence die out more slowly than species with a narrower ecological valence

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.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.