Plasma esterase polymorphism in the Bank vole, Clethrionomys glareolus, in Britain

Abstract

Three hundred and eighty‐three Clethrionomys glareolus from 20 localities in England, Wales and Scotland were typed for plasma esterase and a genetic polymorphism was discovered. The esterase was named Es‐1. Breeding tests suggested that three alleles were segregating: Es‐1o when homozygous results in complete absence of enzyme activity. The active alleles Es‐1f and Es‐1s code for enzyme variants which migrate more rapidly and less rapidly, respectively, under starch gel electrophoresis. Of these active alleles, Es‐1f is morc common in the north of Britain and Es‐18 in the south. A 23‐month field study on two areas at Wicken Fen, Cambridgeshire, suggested that animals possessing Es‐1s survived less well at high population densities, perhaps through their being more likely to emigrate.