Patterns of variation in a number of genetic systems in Maniola jurtina: the boundary region

Abstract

Samples of the butterfly Maniola jurtina have been collected from a number of sites along an east–west transect in southwest England. A number of individuals from most of these samples were analysed for variation in water-soluble esterases by electrophoresis on acrylamide gels. The females showed two polymorphic systems; the first, designated Es–A, has variation with the suggested basis of three alleles at a single locus: Es–A 1 , Es–A 2 and Es–A N the last allele being a null or silent allele, i. e. producing no detectable enzyme. The second system, termed Es–B, has a total of six phenotypes and these have been explained as the genotypes given by three alleles at a single locus: Es–B 0 , Es–B 1 and Es–B 2 all of which produce a functioning enzyme. The males generally gave poor gel preparations, and they seemed to show no variation: all had the Es–A 1 band, and in the Es–B region, bands, when present, were in the Es–B 1 position. The Es–A and Es–B systems appeared to be independent of one another. There is no association between the esterase morphology of a given individual and its hind-wing spotting pattern. The geographical patterns in gene and genotype frequencies of both enzyme systems are described, and these patterns are compared with those shown by spot number and spot position (costality index). The distribution patterns shown by the esterase morphs would seem to emphasize that the boundary region is a zone of ‘genetic disturbance’. The biological meaning of these phenomena is discussed.