James T. Giesel

Genetic correlations of life historical parameters and certain fitness indices in Drosophila melanogaster: r m, rs, diet breadth

SummaryUsing fifteen strains of Drosophila melanogaster which were derived from a collection made at Palm Beach, Florida we found the following:A)Partial genetic correlations between pairs of life history indices which define early reproduction, late reproduction and duration of reproduction are all positive.B)Associations of peak fecundity and first third of life fecundity with age of last fecundity are curvilinear, suggesting that very high values of early fecundity reduce length of reproductive life.C)Intrinsic rate of increase is positively correlated with ability to reproduce under near starvation conditions and with ability to develop on a variety of fruit based media.

Genetic co-variation of survivorship and other fitness indices in Drosophila melanogaster.

Abstract Adult longevity is genetically correlated with larval viability and developmental rate, and with adult fecundity and reproductive homeostatic ability in Drosophila melanogaster. More longevous strains are more viable as larvae and are more able to maintain high levels of fecundity throughout life, with less variation in fecundity due to environmental variation, than are less longevous strains. These results suggest that longevity is directly related to reproductive or Malthusian fitness and to homeostatic ability, and that natural selection must favor the evolutionary accumulation of longevity assurance factors in Drosophila melanogaster.

Larval Photoperiod and Metabolic Rate in Drosophila Melanogaster

The metabolic rate of adult Drosophila melanogaster Meigen is partially determined by larval photoperiod. Generally, flies reared in a short-day environment have higher whole-animal and weight-specific metabolic rates than do flies reared under long-day conditions. The effect of photoperiod on metabolic rate may help explain why short-day flies develop faster and have higher Malthusian fitness than do long-day flies. The photoperiod effect may also facilitate the maintenance of viable populations in seasonally variable environments.

Biology of a duplicate gene system with glucose 6-phosphate dehydrogenase activity in Drosophila melanogaster: genetic analysis and differences in fitness components and reaction to environmental parameters among Zw genotypes.

There are two structural forms of glucose 6-phosphate dehydrogenase activity in Drosophila melanogaster. Whether one or the other or both show in vitro (and probably in vivo) activity depends on the genotype of a sex-linked locus (Zw). In this article, the relative fitnesses of heterozygotes (with both electromorphs active) and homozygotes (with activity demonstrable for only one or the other electromorph) for the Zw locus are described. It is shown that the relative fitness of heterozygotes increases with increase in population density, or degree of crowding and trophic stress, and that the mean development times of Zw heterozygotes are lower than those of the Zw homozygotes. In addition, and perhaps accounting for the fitness and viability excess of the heterozygotes, one set of evidence strongly suggests that they are better buffered against trophic stress than the homozygotes.

The effect of photoperiod on cold tolerance in Drosophila melanogaster.

Abstract 1. 1.|Descendents of Florida and Ithaca, U.S.A. populations of Drosophila melanogaster were reared under short (10 h light: 14 h dark) or long (14 h light: 10 h dark) photoperiods. 2. 2.|Flies were chilled for 8, 16, 32, or 64 min and the time to recovery was recorded. 3. 3.|Recovery time increased as chilling time increased. 4. 4.|Recovery time was also related to photoperiod; short-photoperiod flies recovered faster than did long-photoperiod flies. 5. 5.|These results together with earlier observations of higher metabolic rates of short-day flies indicate the importance of photoperiod in adaptively modifying physiological features.

Diel cycles and measurement of metabolic rates in Drosophila

Abstract 1. 1. Increasing incubation time over which metabolism is measured can provide reasonable estimates of metabolic rates in species with diel cycles. 2. 2. The rates of metabolism of Drosophila melanogaster and D. simulons were measured over consecutive 1-hr intervals to confirm the existence of diel variation. 3. 3. These hourly measurements were integrated over 4- to 9-hr intervals to simulate long incubation times. 4. 4. The estimates of metabolic rate obtained from the 4- to 9-hr intervals closely agreed with the average hourly measurements in both species. 5. 5. Consequently, experiments requiring long measurement intervals that may include periods of fluctuating metabolic rates can provide valid comparative estimates of energy expenditures.

Comparative energetics of a northern and southern population of Drosophila melanogaster

Abstract 1. 1. Weight-adjusted metabolic rates of laboratory-reared, female descendents of Drosophila melanogaster collected from northern New York and northern Florida were compared at 18,21, and 25°C. 2. 2. New York flies had significantly higher rates of metabolism at incubation temperatures of 21 and 25°C but not at 18°C. 3. 3. A nested analysis of variance showed that at 2PC, 29% of the total variance in metabolic rate was due to between-population differences and 27% was due to line differences within populations. 4. 4. The metabolic rate characteristics of both groups of flies are consistent with their patterns of fecundity and seasonal abundance.

Metabolic rate and sexual activity in Drosophila simulans

Abstract The metabolic rates of 4-day-old Drosophila simulans females are affected by sexual activity. Virgin females have the lowest rates of metabolism, inseminated females that were separated from males had higher rates of metabolism, and females that were kept continuously in contact with males had the highest rates of metabolism. Differences between the metabolic rates of the latter two classes of females are unrelated to differences in their rates of egg laying.

Seasonal change in metabolic rate of Drosophila simulans.

1. Second-generation descendents of wild-caught female Drosophila simulans Sturtevant collected at different seasons from Gainesville, Florida, USA, were reared under a constant temperature and food level but with seasonally variable photoperiods. 2. Body weight and metabolic rate, after adjustment to a common body weight, were higher in descendents of flies collected in fall and winter. 3. Temperature sensitivity (Q10) of metabolic rate was also related to season: higher Q10 values were associated with seasons of increasing temperatures and lower Q10 values were associated with seasons of decreasing temperatures. 4. These metabolic characteristics may be adaptive in enhancing activity at lower temperatures and conserving energy at higher temperatures.

Associations between age specific mortality and fecundity rates in mammals.

Abstract As in Drosophila melanogaster , age specific fecundity and, among females, variation in fecundity, vary in parallel with age specific survivorship and death rate, respectively, in many small mammals. The seeming ubiquity of such parallelisms in the light of the fact that schedules of death rate are usually Gompertzian (Sacher, 1977) lends weight to the theory that senescence is an ongoing process involving a general decrementation in vitality.