Evol Ecol Res 8: 803-811 (2006)     Full PDF if your library subscribes.

Adaptive variation among Drosophila species in their circadian rhythms

Angela Simunovic and John Jaenike*

Department of Biology, University of Rochester, Rochester, NY, USA

Address all correspondence to John Jaenike, Department of Biology, University of Rochester, 213 Hutchinson Hall, Rochester, NY 14627, USA.
e-mail: joja@mail.rochester.edu


Observation: In cool, high latitude regions, Drosophila are often active throughout the day, whereas in lower latitudes, they are most active early and late during the daylight hours.

Question: Is this difference in activity due to variation in the conditions experienced by flies in the wild or their perceptual sensitivity to these conditions, or their genetically encoded circadian rhythms.

Methods: The activity patterns of 11 species of Drosophila were recorded continuously in activity monitors under identical 12 h light/12 h dark conditions.

Results: There was a significant positive correlation between the midday activity of flies and the latitudinal midpoint of the species range, showing that behavioural differences in the wild are at least in part genetically based. An independent contrasts test, correcting for phylogeny, confirmed this correlation. Among species from the same latitudinal region, those that inhabit swampy areas and breed on skunk cabbage have significantly greater midday activity than do mycophagous species. Both the latitudinal and breeding site effects suggest that potential desiccation stress has influenced the evolution of their daily activity patterns.

Keywords: desiccation stress, independent contrasts, latitudinal variation, mycophagous insects.

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