. Animal Ecology. Animal ecology. 50 100 150 200 NUMBER OF LARVAE FIG. 16-6 Effect of density of larval populations of Drosophilo melonogasier on number pupating, percentage pupating, and wing length of resulting female adults (after Chiang and Hod- son 1950). size until the per capita consumption of food was cut by one-fourth as a result of the increased number of animals, and then reproduction stopped altogether. It appears that in times of stress the limited energy resources of animals are diverted from reproduction to individual survival (Strecker and Emlen 1953). In another experiment, fo
. Animal Ecology. Animal ecology. 50 100 150 200 NUMBER OF LARVAE FIG. 16-6 Effect of density of larval populations of Drosophilo melonogasier on number pupating, percentage pupating, and wing length of resulting female adults (after Chiang and Hod- son 1950). size until the per capita consumption of food was cut by one-fourth as a result of the increased number of animals, and then reproduction stopped altogether. It appears that in times of stress the limited energy resources of animals are diverted from reproduction to individual survival (Strecker and Emlen 1953). In another experiment, food was supplied in excess but space and cover were restricted. Population in- crease was finally limited by litter mortality from cannibalism and desertion. In some of the popula- tions there was a decline in fecundity. This appeared to be the result of a social hierarchy becoming estab- lished so that subordinated individuals failed to get adequate amounts of food, even though a surplus of food was available, and were prevented from complet- ing their mating behavior (Southwick 1955). Re- productivity has also been found to decline in the short-tailed meadow vole in large populations, be- cause of chasing and fighting, when there was a sur- plus of food and water present (Clarke 1955). Fertility of eggs appears to be high as they are laid under natural conditions. Egg viability, the capacity to hatch, has been shown in Drosophila cul- tures to be modified by the same factors that affect fecundity, particularly the amount of food available to the adult (Robertson and Sang 1945). The survival of young is greatly affected by the number of animals present. When larvae of Dro- sophila are reared at different densities in containers of equal size and with equal amounts of food, the percentage that succeeds in pupating drops in an al- most straight line with increase in density of the larvae. However, because of the larger initial num- bers of larvae present, the actual number pupati
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Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
