Competitive interactions in Drosophila melanogaster: recurrent selection for aggression and response

1988

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Interference, which is one of two aspects of the process of competition which take place in genetically heterogeneous mixtures has been studied in the Texas population of Drosophila melanogaster. Both survival and mean adult weight were investigated in the population itself (which displays high levels of aggression and little response) and in LA, a genotype derived from the population (which displays low aggression and high levels of response) in both homotypically and heterotypically conditioned media. The results presented here show that the competitive effects of conditioning depend not only on the concentration of the conditioned medium but also on the genotype of the larvae which conditioned the medium and that of the flies which respond to such media. It was also concluded that medium conditioning is one of a range of biological parameters involved in the determination of the aggression and response components of the competitive interaction among Drosophila larvae. Thus the competitive fitness of a genotype of D. melanogaster is related not only to genetic variation for aggression and response but also to genetic variation in the ability to condition media and the sensitivity to such media.

Section: Methodsmentioning

confidence: 99%

“…In an earlier investigation (Hemmat and Eggleston, 1988) (1949). In the present investigation the concept of homotypic and heterotypic conditioning is extended to include differences between genotypes within the species D. melanogaster.…”

Section: Introductionmentioning

confidence: 99%

Competitive interactions in Drosophila melanogaster: genetic variation for interference through media conditioning

Hemmat

1988

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“…These are the absolute performance at a standard reference density (e-value); the effects of monoculture density on performance (intra-genotypic competition); the influence of a genotype on the performance of other genotypes (inter-genotypic pressure) and the sensitivity of a genotype to competition from other genotypes (inter-genotypic sensitivity). Recent investigations into the genetic behaviour of these parameters (de Miranda and Eggleston, 1988c) and the related parameters aggression (a) and response (r) (Mather and Caligari, 1988;Hemmat and Eggleston, 1988) have revealed, besides the usual additive variation, high levels of heterosis for intergenotypic pressure and to a lesser extent for the e-values, as well as considerable amounts of dominance for inter-genotypic sensitivity. All dominance and heterosis was directed towards a competitively superior genotype and appeared to be primarily linked to chromosomes U and 111, with a slight emphasis on chromosome III (de Miranda, 1987;de Miranda and Eggleston, 1988c;Mather and Caligari, 1988).…”

Section: Introductionmentioning

confidence: 99%

Analysis of dominance for competitive ability in Drosophila melanogaster

Miranda

1989

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In these experiments the genetic basis of larval competition in Drosophila melanogaster was investigated. Competitive ability was defined by a series of regression coefficients relating larval performance to their mono-and duo-culture densities. Sixteen inter-related F1 hybrids were individually compared with their parents, revealing the presence of large amounts of dominance and heterosis for the various competitive parameters, all directed towards improved competitive ability. Analysis of the F1 hybrids amongst themselves revealed that most of the heterosis was due to either interchromosomal interaction, or the complementing action of haploid autosomes and relatively little was due to any specific interaction between the homologues. The relevance of these results to the current understanding of heterosis is discussed.

“…The resulting parameters simply reflect the average performance of the genotypes within each segregating generation. Eggs were collected from each genotype and seeded into monoculture and duoculture tubes along with eggs of the tester genotype y2, where necessary, as described by Hemmat and Eggleston (1988a). In addition, a monoculture density series for the tester (y2) was raised simultaneously with the rest of the cultures.…”

Section: Methodsmentioning

confidence: 99%

“…Recent investigations using these competitive parameters have improved our understanding of their genetical control. For example, Hemmat and Eggleston (1988a) showed that aggression and response may be adjusted by the selection of particular groups of genes, although the two components do not behave entirely independently. In a chromosome assay experiment using D.…”

Section: Introductionmentioning

confidence: 99%

The biometrical genetics of competitive parameters in Drosophila melanogaster

Hemmat

1990

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Despite the importance of competition as an evolutionary determinant in natural populations there have been few studies of the genetical control of competitive ability. Here, we report the results of a biometrical analysis of four continuously varying traits which, between them, describe the competitive interactions in mixed cultures of Drosophila melanogas fee. The analysis involved the parental, F1, F2 and backcross generations (including all reciprocals) derived from crosses between two highly inbred lines isolated from the Texas population of D. melanogasfer. The competitive performance of each genotype in monoculture and in duoculture with a phenotypically distinct tester were assessed using a yield-density regression analysis. Appropriate genetic models were fitted using a variance weighted least squares procedure and the resulting genetic components of the generation means used to define the genetical architecture of competition. Of the four competitive parameters investigated here the e-value, which describes the competitive performance of the indicator genotype at a fixed reference density, was found to be determined by simple additive genetic effects with no evidence of significant dominance. Conversely, competitive performance in monoculture (intra-genotypic competition) did display a significant net dominance component and the observed values in the F1 and parental generations indicated some degree of heterosis. Of the two competitive parameters determining performance in duoculture (inter-genotypic sensitivity and inter-genotypic pressure) the former was found to have a complex genetic determination involving not only additive and dominance components of the progeny's own genotype but also dominance components of the F1 maternal genotypes. There were also additive-dominance and dominance-dominance non-ailelic interactions. Heterosis was evident, determined both by the progeny's own genotype and by one of the F1 maternal genotypes. All dominance and heterosis was directed towards reduced inter-genotypic sensitivity or, iii other words, superior competitive ability. The analysis of maternal effect components for inter-genotypic competitive pressure could not be accommodated for reasons described in the text, although the data provided evidence for their involvement. The fitting of a simplified model revealed significant additive and dominance components of similar magnitude together with heterosis determined by the progeny's own genotype. There was no evidence of non-allelic interaction. As before all dominance and heterosis was directed towards superior competitive ability (i.e., increased inter-genotypic pressure). Throughout the experiment, there was no evidence for sex-linkage in the determination of competitive parameters. This is thought to be a prerequisite for stability of the sex ratio in the intense competitive environment of natural populations. Possible interpretations of the genetical architecture of competition are discussed in the light of these results.