title: Stasis: a coevolutionary model.
abstract: Traditional neo-Darwinian explanations for stasis involve limited variation, developmental constraints and stabilizing selection. Of these, stabilizing selection is regarded as the mechanism operating most widely. Arguments based on stabilizing selection, however, implicitly assume a one-way evolutionary relationship between organism and environment. In this paper, I suggest that stasis may arise in a number of different ways as a result of organism/environment coevolution. The chief causes of stasis may be the attainment of coadapted equilibria between organism and environment and periods of quiescence within and between arms races. I also suggest that many cases of stasis in the fossil records may be apparent rather than real due to a reliance on gross morphological trends and that apparently large environmental changes during which stasis persists may not reflect change in the coadapted components of the organisms' environment.
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D001522:Behavior, Animal; D005075:Biological Evolution; D004777:Environment; D008954:Models, Biological; D012641:Selection, Genetic