The Ecological Determinants of Population Growth in a Drosophila Culture. III. Larval and Pupal Survival

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

“…This finding supports the hypothesis that some agent (or agents) in the larval metabolic wastes of the conditioning genotype are responsible for the observed decline in survival and mean adult weight of each indicator genotype with increasing concentration of conditioned medium. melanogaster in that conditioning of the growth medium by biotic residues can be responsible for variation in competitive ability and viability Strickberger, 1964, 1969;Sang, 1949;Weisbrot, 1966;and Dolan and Robertson, 1975). In addition we have also shown 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.…”

“…Interference has also been investigated in Drosophila although usually in the context of the competition between different species. These experiments provide evidence which suggests that larval metabolic products might be responsible (in part) for determining the viability of individuals of the same or different species (Sang, 1949;Budnik and Brncic, 1974). Weisbrot (1966) concluded that such medium conditioning, whether by the same or different genotypes, could result either in an improvement or a reduction in viability.…”

The Effect of conditioning the medium in drosophila, in relation to frequency-dependent selection

“…Sang (1949) showed that "larval metabolic products do not impede but may even encourage larval development ". Weisbrot (1966) found that conditioning, whether by the same or by different stocks, could result either in an improvement or in a reduction in viability.…”

“…In the conditioned medium, where the yeast had had 6 or 7 days to develop, the population is presumably larger than in fresh medium. As yeast is the primary food source of the larvae (Sang, 1949), an increased yeast growth in conditioned medium could result in higher larval survival rates.…”

Behavioural correlates of selection for oviposition by Drosophila melanogaster females in a patchy environment

“…It appears to be a norm of the egg-laying behaviour of D. melanogaster females, and poses questions regarding its adaptive significance. An interesting indication here may be given by Sang (1949), who showed that larvae exhibit an undercrowding as well as the more familiar overcrowding effect with respect to survival under certain conditions. Larval density can be suboptimal.…”