GENETIC ANALYSIS OF THE POLYMORPHISM OF COLOR PATTERN INDROSOPHILA POLYMORPHA

Abstract

Natural populations of most species of Drosophila are very uniform in external morphology. This uniformity is a serious drawback of Drosophila as material for studies on population genetics. Since genetic analysis is predicated upon existence of genotypic variability among materials to be studied, traits other than externally visible structures had to be used in genetic population studies on Drosophila. Variations in the gene arrangement in chromosomes, and recessive genes carried in populations concealed in heterozygous condition, have been investigated by many authors. These investigations have led to great advances in our understanding of the evolutionary mechanisms that operate in Drosophila as well as of general problems of population genetics. The labor involved in detection and study of chromosomal variants and of concealed recessive genes is, however, considerable; a species of Drosophila with genetically determined discontinuous variability in external traits in natural populations would have a clear advantage over species hitherto used. Two such species are known, Drosophila polymorpha Dobzhansky and Pavan (1943) and D. montium de Meijere (see Duda 1924); both show heritable variations in the color pattern of the abdomen. In the first of these two species the variation is caused almost entirely by a single gene, the heterozygotes and the two homozygotes being phenotypically recognizable. The present article reports the results of a study of populations of D. polymorpha which inhabit the states