Larval competition in Drosophila melanogaster. I. Estimation of larval growth parameters

Abstract

Despite extensive research into the competitive interactions between the larvae of Drosophila for food, there have been few studies of the biological characteristics of the larvae which might underly competition. Here we present a sensitive method for estimating the larval feeding rate, larval gut capacity, larval conversion efficiency and larva-adult conversion efficiency, using radioactively labelled yeast. Two developmental stages, defined by the time since oviposition, were investigated in eight genetically distinct strains of Drosophila melanogaster. Significant genetic variation was recovered for all parameters at the second instar but only for conversion efficiency at the third instar. Feeding rate and the gut capacity had large and heterogenous error variances, especially in the third instar, while conversion efficiencies were relatively more stable.

Larval competition in Drosophila melanogaster. II. Comparing biological and competitive parameters

“…In short, competition took place in glass vials each with 50 ml 2 per cent bacto agar as a non nutritive base, and 55O mg live yeast (Sigma YSC-2) as the food source. The wild type inbred strains used in the experimental conditions are identical to those used for the determination of the larval feeding parameters (de Miranda and Eggleston, 1987b Where T5, T27, T19 and T25 refer to four inbred lines derived from the Texas population (Linney et a!., 1971).…”

“…Significant genotypic variation exists for both Pa and 1/ui' (=84916 and X7)= 523161 respectively). The relationships between the biological parameters defined in the accompanying paper (de Miranda and Eggleston, 1987b) and the estimates of aggression and response are described in table 4. The estimates of aggression and response used are those that exclude the values for intra-genotypic competition since this improves both the primary and partial correlations.…”

“…Only larval feeding rates (b53 and b77) and larva-adult conversion efficiencies (n53 and n77) are considered in table 4. Larval conversion efficiency (also investigated by de Miranda and Eggleston, 1987b) showed little correlation with either competitive parameter, and was excluded from further analysis. ability assumes that all larval mortality is due to the effects of competition and that at low densities survival is high and near the percentage egg hatchability.…”

“…Here we report the competitive characteristics of genotypes previously investigated with respect to a variety of biological parameters which might be related to competition (de Miranda and Eggleston, 1987b). Correlation analyses are used to define the relationships between the biological parameters (larval feeding rate and larva to adult conversion efficiency) and the competitive parameters.…”

The competition diallel and the exploitation and interference components of larval competition in Drosophila melanogaster

“…The feeding rate differences will tend to produce a negative correlation between the row and column means, but variation for the utilization efficiency (u) will disrupt this correlation. Dividing all indicator c-values by their corresponding monoculture c-value removes the variation due to the differences in u (and any effects of a correlation between utilization efficiency and feeding rate, de Miranda & Eggleston, 1988a) and should improve the negative correlation between sensitivity (rows) and pressure (columns) caused by the feeding rate differences. The most important feature of such a corrected diallel is that the duoculture gains and losses should cancel, i.e.…”