The Existence of a Protected Polymorphism Under Conditions of Soft as Opposed to Hard Selection in a Multideme Population System

Abstract

The role for maintaining polymorphism of the time of occurrence during the life history of selection in subdivided [animal] populations (which has also been interpreted as reflecting density- and frequency-dependent selection) is studied by contrasting hard and soft selection. The case of total panmixia (Levene migration) and other well-studied migration patterns (Deakin, circular stepping-stone, clines) provide a protected polymorphism more readily under soft selection than under hard selection (hard protection implies soft protection) for fixed migration and selection parameters. There are selection-migration regimes which will maintain a polymorphism under hard selection although not under soft selection, but at least 3 habitats are necessary for such a circumstance and the known examples involve unnatural migration and rather extreme selection parameters. The analyses are also relevant for studying some concepts of more migration and averaged environments with respect to polymorphism.