Experimental Populations of Drosophila persimilis from an Altitudinal Transect of the Sierra Nevada

GENETICS OF MARGINAL POPULATIONS OFDROSOPHILA WILLISTONI

“…The biological significance of these two types of variability is quite different. Chromosomal polymorphism has been shown to be adaptive and balanced in every Drosophila species examined in this respect-namely, D. pseudoobscura (Wright and Dobzhansky, 1946;Dobzhansky and Levene, 1948), D. persimilis (Spiess, 1950), and D. robusta (Levitan, 1951). Although the adaptive values of the chromosomal inversions in D. willistoni have not been studied experimentally, da Cunha, Burla, and Dobzhansky (1950) have adduced arguments which make it virtually certain that the chromosomal polymorphism in this species is also balanced.…”

INTERACTION OF THE ADAPTIVE VALUES IN POLYMORPHIC EXPERIMENTAL POPULATIONS OFDROSOPHILA PSEUDOOBSCURA

“…I t should be kept in mind that the experiments described in this article have been made at 25 0 C. At 16 0 C. the adaptive values of these karyotypes are very near equality (Wrigh t and Dobzhansky, 1946;Dobzhansky, 1949). Yet, Spiess (1950) discovered that in the closely related D. persimilis the karyotypes have different adaptive values at 16 0 C. but tend towards equality at 25 0 C. Again the adaptive value of a karyotype depends on the species of microorganisms which the flies use for food (da Cunha, 1951 and unpublished experiments of Dobzhansky and Spassky). Finally, the data presented in this article show that the adaptive value of a karyotype is modified by the presence of individuals with other karyotypes in the same environment.…”

RELATION BETWEEN FREQUENCIES AND ADAPTIVE VALUES OF CHROMOSOMAL ARRANGEMENTS INDROSOPHILA PERSIMILIS

“…biological. factors: temperature, huIdIty, fo~d microorganisms, and population density (Birch, 1955;da Cunha, 1951;Levitan, 1951;Spiess, 1950). The genetic constitution of the members of a population might also participate in the modification of adaptive values.…”

“…Experimental populations testing for relative adaptive values of chromosome III arrangements from Drosophila persimilis were initiated for four reasons: 1) Spiess (1950) had shown these arrange-ments to be adaptive under laboratory conditions at 16 0 c., but a more extensive analysis using flies from new localities for comparison with other populations of the Yosemite transect was needed; 2) rare inversions had not yet been tested together or in triple combination with the common arrangement (Whitney) ; 3) it was desirable to compare' adaptive values obtained when two inversions compete with those when three occur in a population; and 4) a demonstration of adaptive values was sought to accompany other studies on physiological properties of these arrangements (Spiess and Schuellein, 1956 (Wright and Dobshansky, 1946;Dobzhansky and Pavlovsky, 1953;Spiess, 1950 …”