INCREASING TREND IN FREQUENCIES OF LETHAL AND SEMILETHAL CHROMOSOMES IN A NATURAL POPULATION OF <i>DROSOPHILA MELANOGASTER</i>

Homeostasis, enzymatic heterozygosity and inbreeding depression in natural populations of Drosophila melanogaster

“…Band andIres (1961, 1968) and Band (1972) also found that the frequency of lethal factors was correlated with climatic factors as rainfall. However, in other studies, no effect of such climatic factors was observed on the frequency of lethals and scmi-lcthals (Minamori et al, 1973). Several studies of Drosophila have also failed to show any' dominance of lethal heterozygotes or any evidence that heterozygotes for one or two lethals differed in viability from any, other heterozygotes; but, nevertheless, some lethals were found to be slightly hctcrotic (see Lewontin, 1974).…”

“…The author then concluded that the adaptive value of some lethal heterozygotes is high during winter but then in the period from summer to autumn it decreases. However, such differences in frequency of lethals between seasons do not seem to be a general phenomenon (Sperlich, Jaksh & Karlik, 1963;Minamori et al, 1973) and Minamori and Saito (1964) observed that the lethal plus semi-lethal frequency increased and allclism frequency decreased from early summer to fall in each },ear.…”

Genetic changes in a Korean population of Drosophila melanogaster.

“…Genetic changes in deleterious genes in natural populations of D. melanogaster have been reported by Band and Ives (1968) in South Amherst, U.S.A., Minamori et al (1973) in Hiroshima, Japan, and Watanabe et al (1976) in Katsunuma, Japan. They described frequency changes in lethal or semilethal chromosomes in each population and discussed whether or not the respective genetic changes might be related to such environmental changes as climate, overwintering conditions, insecticide pollution, etc.…”

Effects of winter on genetic structure of a natural population of Drosophila melanogaster

“…Indeed, it was reported that individuals with no lethal alleles were highly heterozygous for enzymatic loci (PASTEUR, 1974 ;S TEINER , 1979), a quantitative trait (P REVOSTI , 1955) and frequencies of lethal and semi-lethal alleles (M INAMORI & S AITO , 1964;G OLUBOVSKY , 1970 ;O SHIMA et al, 1971). However, other studies failed to show any significant seasonal variation for either allozyme or inversion (LA N GL E Y et al, 1977 ;CA VE N ER & C LEGG , 1981) or deleterious genes (S PERLICH et al, 1963 ;M INAMORI et al, 1973). The (B AND & IVES, 1961, 1968B AND , 1963).…”