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J W Curtsinger

Publications and source records attributed to J W Curtsinger.

42 records · Page 3Linked to original sources
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Deceleration of age-specific mortality rates in chromosomal homozygotes and heterozygotes of Drosophila melanogaster.

Age-specific mortality trajectories were estimated in mixed-sex cohorts of D. melanogaster. We studied 22,000 flies that were either second-chromosome homozygotes or heterozygotes with a randomized genetic background. Broad-sense heritabilities for longevity were estimated to be 6% for males and 9% for females. Heterozygotes lived longer than homozygotes on average, but there were exceptions to the usual heterotic pattern; in several crosses parental homozygotes had average life spans as long as that of their F1 heterozygotes. Estimated age-specific mortality rates were found to decelerate at advanced ages in both homozygotes and heterozygotes. The mortality models that best fit the data are the logistic model and the two-stage Gompertz model, both of which produce mortality trajectories that level off at advanced ages. Old-age mortality deceleration is not peculiar to inbred Drosophila.

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Stabilizing selection in Drosophila melanogaster.

Stabilizing selection operates on egg length in Drosophila melanogaster. The percentage of eggs hatching decreases with departure from the population mean size; this effect cannot be explained by the model of neutral variation in a quantitative character. The finding of stabilizing selection agrees with expectations for a character inherited primarily through additive effects.

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Quantitative wing variation in inbred and outbred lines of Drosophila melanogaster.

Variation of two wing morphology characters was studied in 11 X-chromosome substitution lines and three outbred lines of D. melanogaster, as a test of quantitative genetic predictions regarding variance components and heritabilities. As expected from inbreeding of the lines, between-lines components of phenotypic variance are statistically significant, while the significant within-line component is attributable to a maternal effect. Unusually low broad-sense heritabilities were observed in the inbred lines, and unusually low narrow-sense heritabilities were observed in the outbred lines. Low heritability estimates cannot be explained by insensitive measurement techniques, since the techniques were sufficiently sensitive to detect significant maternal effects. The most likely explanation for the low heritability estimates is the operation of natural selection on wing or correlated characters as stocks adapt to the laboratory environment.

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Frequency-dependent viability in mutant strains of Drosophila melanogaster.

We investigated the effects of genotypic frequencies on egg-to-adult viabilities in pairwise combinations of four strains of Drosophila melanogaster. The experiments involved mixture of a total of 42,000 eggs in varying proportions under controlled densities and observation of surviving adults. Viabilities were found to depend on frequencies in several genotypic combinations. In the most extreme case, the absolute viability of cn;bw females increased monotonically from 54% when common to 70% when rare. The results illustrate several statistical and methodological problems that might explain why some experiments have failed to detect frequency-dependent viabilities. These problems include heterogeneity between replications, sex differences in susceptibility to competition, and strong dependence of the experimental outcome on the choice of competitor genotypes.

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