Allozyme genotype-environment relationships in natural populations of Drosophila buzzatii

Abstract

Allozyme frequency data from natural populations of Drosophila buzzatii were analyzed for genotype--environment relationships. Allele frequency and heterozygosity at six loci polymorphic throughout eastern Australia and a number of environmental factors (both means and variabilities) were examined by a variety of multivariate techniques. Significant genotype--environment associations were found for five of the six loci, and after correcting for geographic location significant associations remained for Est-2 and Adh-1 gene frequencies and heterozygosities and for Pgm gene frequencies. The results are discussed in relation to selection and gene flow and provide the basis for laboratory studies to disentangle confounded effects of (1) environmental means and environmental variabilities and (2) allele frequency and heterozygosity, and thus to further test for and determine the nature of any natural selection at particular allozyme loci.

Polymorphic Inversion and Esterase Loci Complex on Chromosome 2 of Drosophila buzzatii II. Spatial Variation

“…Similar analyses for Est-l allele frequencies unadjusted for inversions are also tabulated to enable comparisons with the previous analyses of Mulley et al (1979) and Sokal et al (1987). As expected from the preceding analyses, there were many significant spatial and climatic associations for conditional Est-l allele frequencies that were not evident without adjustment for inversions.…”

“…As expected from the preceding analyses, there were many significant spatial and climatic associations for conditional Est-l allele frequencies that were not evident without adjustment for inversions. Following the rationale of Mulley et al (1979) for inferring evidence of selection from climatic associations, we repeated the analyses of Table 4 after controlling for spatial variables. Then only one of the 17 associations originally significant in Table 4 remained so, and one case out of 17 could be accounted for by chance.…”

“…To investigate the evolutionary processes that have given rise to this population differentiation, Mulley et al (1979) used canonical correlation and multiple regression procedures to test for associations of allozyme frequencies (and heterozygosities) with spatial and climatic variables. The rationale was that while associations with spatial variables could be due to drift and/or migration, any with climatic variables after correction for geographic location would indicate possible differential selection in different populations.…”

Frequency and temperature dependent selection at the alcohol dehydrogenase-1 locus of Drosophila buzzatii

“…This discrepancy may be because the range of temperatures tested in this study is much narrower than those which D. buzzatti experience in the wild, or because of the homogeneity of the laboratory environment in contrast to diurnal temperature variation in the field, or because effects on larvae are compensated by different effects at other life cycle stages. Clinal variation for the Adh polymorphism in D. melanogaster has been well documented (Oakeshott et al, 1982b) and a study of D. buzzatii Adh-1 allele frequencies in eastern Australia showed significant spatial heterogeneity, with Adh-1" frequency decreasing with increasing distance from the coast and increasing latitude (Mulley et a!., 1979). In a laboratory study of the effects of cold shock (0°C for 5 days), a decrease in the frequency of Adh-1" was found among survivors (Watt, 1981).…”

“…Several field and laboratory studies have suggested that temperature may be a selective agent on Adh-1 allele frequencies in D. buzzatii (Mulley et a!., 1979;Watt, 1981;Barker et aL, 1986). This study was designed to determine the effects of rearing temperature on genotype frequencies in laboratory populations of D. buzzatii over one generation.…”