Genetic analysis of larval competition in Drosophila melanogaster.

A chromosome assay was employed to determine the genetic basis of the competitive ability of the larvae of Drosophila melanogaster when competing for a controlled amount of food. The effects of increasing stress due to intra- and inter-genotypic competition were analysed using a yield-density regression analysis producing estimates of the absolute performance at a standard reference density (e-values), the magnitude of intra-genotypic competition and the inter-genotypic competitive effect of one genotype on another. A distinction was made between the Sensitivity and the Pressure components of inter-genotypic competition. The probability of survival and mean adult weight were used as measures of competitive success. The genetic analysis revealed high levels of heterosis for the e-values and inter-genotypic pressure, with correspondingly high inter-chromosomal interactions. Inter-genotypic sensitivity was less consistently heterotic and less epistatic. All dominance was directed towards a competitively superior genotype and both major autosomes were involved in the determination of competitive ability with the greater effect residing on the third chromosome. There was evidence of early non-competitive larval mortality in one of the two sets of substitution lines investigated and the effect of this on the estimation of the genetic parameters is discussed.