Numerical Changes and Environmental Utilization in Natural Populations of Drosophila.

Abstract

Monthly collections of three Drosophila species were made over a 39-month period. D, melanogaster was found to be the most common species during summer, D. sirnulans during autumn and D. irnrnigrans during winter. Numerical fluctuations were most marked in the first two species and were related to macroenvironmental temperature. The D. irnmigrans population remained relatively constant throughout the year and the number of the species collected was independent of macroenvironmental variation. For all three species the dimensions of the niche were related to macroenvironmental temperature. This result is discussed in relation to the interaction between numbers in the population, the niche breadth of the species and the environment.