Studies of esterase 6 in Drosophila melanogaster XII. Evidence for temperature selection of Est 6 and Adh alleles

Abstract

Changes in allele frequencies at the esterase 6 (Est 6) and alcohol dehydrogenase (Adh) enzyme loci of Drosophila melanogaster and simulans are examined in natural populations and artificial populations maintained at two temperatures. Results from cage populations at 18 °C and 25 °C provide evidence for temperature selection at both loci. Seasonal population samples show no significant change in gene frequencies for either locus, a reasonable outcome given the small selection coefficients found in cage populations. The temperature effect for the Adh locus appears to be direct: natural selection of the fast allele in cool environs and of the slow allele in warm environs. The temperature effect for Est 6 is weaker and complicated by sex differences and deviations from Hardy-Weinberg expectation. This evidence and different Est 6 frequencies found for melanogaster and simulans, in conjunction with evidence of the male reproductive function of this enzyme, suggest that Est 6 polymorphisms are maintained in natural populations by a complex form of sexual selection.

Est-6 in Drosophila melanogaster: effects of genetic composition, temperature and oviposition period on fitness in laboratory populations polymorphic for rare alleles

“…It has by now become evident that the Est-6 polymorphism has an adaptive significance based either on its already demonstrated involvement in the reproductive process (Gilbert and Richmond, 1982) or on its role in the metabolism of esters (Zera et a!., 1983;Costa et a!., 1985). The results reported here together with the other findings for outbred and inbred populations cited above, suggest however that the Est-6 locus is not only involved in selective processes per se but also because of its interactions with other loci.…”

“…It seems worth considering the hypothesis that this interaction is due to a difference in the pattern of oviposition among genotypes. Previous results (Gilbert and Richmond, 1982) have suggested that male Est-6 promotes ejaculate transfer, sperm storage and use in females. A quantitative study of sperm use during the first 50 hours after mating by using Est-6 null and active stocks of Drosophila melanogaster (Gilbert et a!., 1981) demonstrated that the rate of sperm release is related to the level of Esterase-6 activity suggesting the involvement of this enzyme, present in the seminal fluid, in sperm motility.…”

“…1.1.1., Wright, 1963) seems to be involved in the mechanism of reproduction affecting both storage and use of sperm in females (Richmond et al, 1980;Richmond and Senior, 1981;Gilbert, 1981;Gilbert et a!., 1981). The involvement of Esterase-6 in sperm use and daily productivity in terms of progeny is known to be affected by temperature (Gilbert and Richmond, 1982). Moreover Esterase-6 together with a male specific lipid (cis-vaccenylacetate), a component of the seminal fluid, seems to constitute a substrateenzyme system that is involved in the pheromonal regulation of the timing of remating in females (Mane et aL, 1983).…”

Selection in highly inbred populations of Drosophila melanogaster polymorphic at a single locus

“…In the case of methylmalonate, we suggest that the selective action could be caused by a cleavage product of the substrate (malonate) which is a powerful inhibitor of succinate dehydrogenase, and should have a negative effect on respiration. Sexual selection (Gilbert and Richmond, 1982) through allozymic differences in reproductive functions such as sperm use and mating and remating behaviour, has been demonstrated to be one of the most likely mechanisms responsible for the maintenance of the Est-6 polymorphism. Our results, concerning laboratory populations set up with forced matings, indicate that the catalytic function(s) of Esterase-6 in ester metabolism can also be a target of selection.…”

“…This polymorphism has been studied in laboratory populations with a variety of approaches by many workers. Evidence for selection mainly dependent on frequency, temperature and density, and involving the chromosomal regions carrying genetic variability for the Est-6 locus has been produced (Maclntyre and Wright, 1966;Kojima and Yarbrough, 1967;Birley and Beardmore, 1977;Costa and Beardmore, 1980;Gilbert and Richmond, 1982). Moreover, it has recently been demonstrated that the Esterase-6 allozymes are involved in reproductive processes (Richmond et al, 1980); Esterase-6 seems to influence female productivity and the timing of subsequent remating (Gilbert, Richmond and Sheehan, l98la, b;Gilbert and Richmond, 1981;Richmond and Senior, 1981).…”