Nonequilibrium Population Structure in Forked Fungus Beetles: Extinction, Colonization, and the Genetic Variance Among Populations

Abstract

Local extinction and recolonization play a significant role in determining the amount of genetic variance among populations of Bolitotherus cornutus, the forked fungus beetle. Several demographic parameters are known to be important to genetic differentiation; the local population size distribution, migration rate, extinction rate, colonization number, and the probability of common origin of colonists were measured for forked fungus beetles. An artificial colonization site experiment demonstrated that the numbers of colonists and migrants per generation are approximately equal. These observations, interpreted with previous theoretical analyses, predict that the genetic variance among populations is increased in Bolitotherus relative to the case of long-lasting populations at an equilibrium between drift and migration. An electrophoretic comparison of populations of different ages supports this prediction. Young populations are more differentiated than older populations; the effect of the extinction/recolonization process in this species is to increase the genetic variance among populations. This study provides a methodology based on recent theory that can be applied to the study of the effects of local extinction and recolonization in other species.