Intra- and Interpopulation Selection concerning the Alcohol Dehydrogenase Locus in Drosophila melanogaster

Abstract

Lewontin and Hubby¹ have shown, by means of protein electrophoresis, that about one third of the loci in Drosophila pseudoobscura populations are polymorphic. Comparable studies by others have provided similar figures for a variety of species including man^2,3. Some authors^4–6 have argued that the observed protein variation is merely a product of mutation and drift of neutral variants and is not maintained by selection. This view is severely criticised by others^7,8, who stress the importance of selective forces. Indications for the operation of selective forces have mainly come, until now, from studies on geographical variation^9,10. Direct experimental evidence, concerning the relative selective values of electrophoretic variants is, however, scarce. In one well-documented case, Yamazaki¹¹ did not find selective differences between esterase-5 variants in D. pseudoobscura.