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ItemThe analysis of quantitative variation in natural populations with isofemale strainsHOFFMANN, AA ; PARSONS, PA (BioMed Central, 1988-03-01)Isofemale strains are having an increasing role in the analysis of variability of ecological and behavioural traits in natural populations. This paper therefore considers the association between heritability and phenotypic variation within and between isofemale strains. Heritability from an isofemale strain analysis approximates narrow heritability over a wide range of dominance values, particularly when genes contributing to variation in a trait are at intermediate frequencies. Meaningful heritability estimates require that isofemale strains are maintained at a population size greater than 50 and tested within 5 generations after establishment. Values of heritabilities for morphological traits in Drosophila melanogaster were similar to those estimated from a conventional sib analysis. Published data on isofemale strains can therefore be put into a theoretical framework. The contribution of isofemale strain analyses to the debate about the number of loci affection variation in quantitative traits is briefly discussed.
ItemPopulation-genetics of the metabolically related Adh, Gpdh and Tpi polymorphisms in Drosophila melanogaster: II. Temporal and spatial variation in and orchard populationNIELSEN, KM ; HOFFMANN, AA ; MCKECHNIE, SW (BioMed Central, 1985-01-01)Seasonal and spatial variation in gene frequencies at 3 diallelic loci : alcohol dehydrogenase (Adh), glycerophosphate dehydrogenase (Gpdh) and triosephosphate isomerase (Tpi), have been studied in an orchard population of D. melanogaster. Gene frequency at the Tpi locus varied seasonally and was associated positively with total monthly rainfall measured both immediately prior to and concurrent with the month of collection. Temporal herteogeneity, not associated with the environmental parameters, was present at the Adh locus. Gpdh-F frequency was negatively associated with mean monthly maximum temperature measured prior to the time of collection. Within the orchard site, spatial heterogeneity in gene frequency at the Tpi locus was observed within collections. a deficiency of Gpdh heterozygotes was observed in individual trap samples and among collections with traps pooled. Overall, this variation is interpreted as being due to sampling from a population of partially isolated subgroups, founded by few individuals, and dependent upon transient pockets of fruit resources.
ItemBidirectional selection for olfactory response to acetaldehyde and ethanol in Drosophila melanogasterHOFFMANN, AA (BioMed Central, 1983-01-01)Drosophila melanogaster adults were successfully selected for increased and decreased olfactory response to different concentrations of acetaldehyde and ethanol, using a choice type olfactometer. The response to selection was not concentration specific. Lines were also tested with n-propanol, n-butanol, acetic acid, propionic acid, benzaldehyde, methyl acetate, ethyl acetate and 3-hydroxybutan-2-one. The behavior of the lines was similar for most of these chemicals, indicating an odorant specific response to selection. However, ethanol selected lines differed in their response to n-propanol and possibly n-butanol, suggesting a role for the alcohol group in determining the specificity of genetic variation in olfactory response. Utilization of acetic acid, ethanol and acetaldehyde as resources by the selected lines was tested using adult longevity. The only significant result was that lines selected for increased attraction to ethanol ulitised 9 p. 100 and 12 p. 100 ethanol more than lines selected for decreased attraction. Gene frequencies were monitored at 3 enzyme loci – alcohol dehydrogenase, triose phosphate isomerase, α-glycerophosphate dehydrogenase – associated with the metabolism of ethanol and acetaldehyde. There were no changes associated with the metabolism of ethanol and acetaldehyde. There were no changes associated with the response to selection, and the ADH-F allele increased in both selected and unselected lines.