Diurnal Temperature Fluctuation and Genetic Variance in Drosophila Populations

Abstract

FOUR populations of Drosophila pseudo-obscura were started from a common founder stock in November 1956, by Dr. L. Levine and me. Since that time, two of them, K 1 and K 2, have been maintained under conditions of temperature which, while slightly differing from year to year, have always been constant diurnally. Concurrently, the populations V 1 and V 2 have been kept in diurnally fluctuating conditions with again slight difference of mean from year to year, but always : (1) with the same mean temperature as the K populations and (2) undergoing a regular 10° C. oscillation of temperature during each period of 24 hr. A more detailed account of this type of environment will be found in a recent publication¹. All populations were initially polymorphic for the two gene-arrangements Arrowhead and Chiricahua (q ₀ = 0.5), of the third chromosome, and all populations are now largely, if not completely, monomorphic². The changes in the polymorphic system which appear to be similar in both K and V populations will be discussed elsewhere (Beardmore, J. A., and Levine, L., in preparation).