CONTINUING STUDIES ON THE SOUTH AMHERST DROSOPHILA MELANOGASTER NATURAL POPULATION DURING THE 1970'S AND 1980'S.

Continuing investigations on the South Amherst Drosophila melanogaster natural population following the significant decline and recovery of lethal (le) and semilethal (sle) frequencies in the late 1960's (Ives, 1970) show that the population has been remarkably stable although it contains MR (male recombination) and/or P DNA elements (Kidwell et al., 1977a; Green, 1980). A 13-year study affirms that the lethals present are nonrandomly distributed along the second chromosome and deficient on the right; they differ significantly in distribution from spontaneous (Ives, 1973) and δ-induced lethals (Minamori and Ito, 1971). Between 1970 and 1977, a total of 4,083 second chromosomes from the Markert subpopulation were analyzed; 28.9% of the chromosomes were lethal and 7.25% were semilethal in homozygous condition. Frequencies are similar for early summer and late fall collections although the rate of allelism among lethals is significantly higher in early summer than in late fall. For the large fall (1970-1979) Porch site population, 2,519 second chromosomes were analyzed; 29.5% were lethal and 8.0% were sublethal as homozygotes; the rate of allelism among lethals was 1.50%. At Hockanum, 1977-1983, lethal and semilethal frequencies were lower; the rate of allelism among lethals was 1.43%. The chromosome map distribution of lethals does not change between summer and late fall at Markert. The overall distributions of lethals at the Markert and Hockanum sites are similar. In tests for male recombination (MR) activity in the population over a 6-year period, a total of 0.47% recombinants were observed; these were uniformly distributed along the second chromosome. Comparisons are made with other long studied D. melanogaster populations.

The existence of LSP-1 beta S in Drosophila melanogaster natural populations in two northern states.

LSP-1 beta S is present in Michigan and Massachusetts Drosophila melanogaster natural populations. Its frequency, 10%, is significantly higher in an East Jordan, Mich. (latitude, 45.10 degrees N), population than in East Lansing, Mich. (latitude 42.44 degrees N), or Hadley, Mass. (latitude, 42.21 degrees N), populations, where it averages 3% at each location. The average frequency of LSP-2S is more comparable, 6, 5, and 7% at East Jordan, East Lansing, and Hadley, respectively. LSP-1 gamma F variants are also present. A total of 342 single third-instar larvae was scored for LSP-1 autosomal variants, and 323 for LSP-2 variants. Each larva represented a newly established isofemale line from collections at East Jordan in 1981 and 1983, East Lansing in 1982, and Hadley in 1981, 1982, and 1983. Within localities, frequencies of hemolymph protein variants did not differ significantly between years. Proteins 9, 10, 11, and 15 correspond to the LSP-1 gamma, beta, and alpha triplet and LSP-2 polypeptide in D. melanogaster. Our results together with those of Singh and Coulthart [(1982). Genetics 102:437] indicate that D. melanogaster populations in north temperate climates maintain considerable genetic heterogeneity for the larval hemolymph proteins.

A survey of isozyme polymorphism in a Drosophila melanogaster natural population.

A survey of biochemical polymorphism among glucose- and non-glucose-metabolizing enzymes was carried out on the June 1973 collection from the South Amherst, Mass. Drosophila melanogaster natural population. Polymorphic levels are among the highest recorded for this species; polymorphism among glucose-metabolizing enzymes did not differ significantly from that among non-glucose-metabolizing enzymes. Two loci, G6Pd on the X and Est-6 on the 3rd chromosome, displayed significant excesses of heterozygotes. Adh on the 2nd and Idh, Odh and Ao on the 3rd chromosome showed significant heterozygote deficiencies. Idh is ten map units to the left of Est-6, Odh twelve map units to the right and Ao is seven units beyond Odh. Temperatures in the two-week June period prior to collection were exceedingly variable. Daily high/low ranged between 76 degrees/40 degrees and 97 degrees/65 degrees F. These results support the findings of Frydenberg and Simonsen (1973) that in some populations glucose-metabolizing enzymes tend to be as polymorphic as non-glucose-metabolizing ones. They also add to the evidence obtained from other plant and animal populations that increased biochemical polymorphism is associated with more variable and/or colder climates. The increase may in part be due to increased polymorphism among glucose-metabolizing enzymes. Comparisons utilizing published data on other D. melanogaster populations and on D. robusta indicate a clinal increase in heterozygosity among glucose-metabolizing enzymes as one moves northward.