The Effect of Overlapping Generations and Population Structure on Gene-Frequency Clines

Abstract

Many natural populations exhibit clines or spatial patterns in gene frequency or phenotype (Roughgarden 1979). The maintenance of these clines is understood as a balance between the diversifying process of spatial variation in selection intensities and the homogenizing process of gene flow or migration. A quantitative analysis of the amount of gene flow necessary to prevent genetic differentiation between two populations is also directly related to theories of speciation, in particular, that of parapatric speciation (Slatkin 1973). In this chapter, we extend previous models of clines to examine the effects of population structure and overlapping generations in clines maintained by the balance between selection and gene flow.