Study
Genetic shift in photoperiodic response correlated with global warming
Bradshaw, William E.; Holzapfel, Christina M.
Proceedings of the National Academy of Sciences, 2001
Populations of the pitcher-plant mosquito were collected along a latitudinal gradient in North America and their critical photoperiod — the day length at which larvae enter diapause — measured under controlled light regimes in the laboratory. The measurements were compared against equivalent measurements made on the same populations decades earlier.
- Studied in
- Wyeomyia smithii
- Sample size
- populations of the pitcher-plant mosquito resampled across decades
Critical photoperiod shifted towards shorter day lengths over the intervening decades, in the direction characteristic of more southern populations, and the shift was larger in northern populations where the growing season has lengthened most. Because critical photoperiod is measured under controlled laboratory light and is heritable, the change is genetic rather than a plastic response to conditions.
What it means
The authors' reading, and ours. Where they differ, that difference is the point.
How the authors put it
The seasonal timing mechanism itself has evolved in response to a lengthening growing season, rather than organisms merely responding plastically to warmer conditions.
How NatureHQ reads it
This is the strongest available answer to whether the calendar itself can move. It can: the animals did not simply behave differently in warmer weather, they changed the day length at which they act. What it does not settle is the rate question, and the rate question is the whole problem — a mosquito runs several generations a year and a long-lived vertebrate does not, so a result that is encouraging here says very little about a bird.
- One species, chosen because its photoperiodic response is exceptionally well characterised.
- Historical measurements were made by different workers with different equipment, though using the same assay.
- Correlation with warming is inferred from the direction and geography of the shift rather than from a manipulation.
Measuring the same mosquitoes decades apart, in a light cabinet
Seasons are shifting and organisms are responding. Is the seasonal timing mechanism itself evolving, or are animals simply reacting to warmer weather?
What this study is used for on NatureHQ
One study can inform several subjects. Here is everywhere this one is cited.
Published by: Proceedings of the National Academy of SciencesPublished in PNAS.
doi.org/10.1073/pnas.241391498
This reference was resolved automatically against Crossref on 2026-08-11.
NatureHQ summarises research in its own words and does not reproduce published text. Reviewed 2026-08-11.