Genetic drift in a visibly polymorphic spider Enoplognatha ovata— antidote to the peppered moth

Abstract

The belief that visible polymorphisms are necessarily subject to powerful natural selection merely because they aro visible is tempered with a counter example involving a common and widespread spider, Enoplognatha ovata. This species exhibits a vivid red and yellow pattern polymorphism comprising three principal morphs. Observational and experimental evidence is presented which indicates that in local populations genetic drift is the predominant force determining morph frequencies. However, it is argued that some form of polymorphism-promoting selection is ultimatelyresponsible for maintaining the variation. Ways of utilizing this species as a teaching aid are suggested.

Keywords:

• Enoplognatha
• Colour polymorphism
• Genetic drift