1. Diapause is considered an important adaptation for survival of winter; however, insects often enter diapause long before its onset. Thus, diapausing insects must also be able to survive these prewinter conditions which warm temperatures could make quite energetically taxing despite relative inactivity.

2. We tested for both immediate and delayed fitness effects of prewinter conditions in diapausing Pieris napi butterfly pupae, experimentally exposing them to different prewinter treatments in a factorial design. We placed diapausing pupae at one of three temperatures (15, 20, 25 °C) for 1 to 16 weeks, followed by the same standardized winter for all individuals.

3. We monitored survival at multiple points during the experiment, including after winter, as well as their change in mass. For a subset of individuals, we also made repeated metabolic measurements.

4. We found substantial weight loss during prewinter warm periods, greater during longer prewinter treatments at higher temperatures. This weight loss was associated with elevated metabolic rates at higher temperatures which increased over the duration of the prewinter treatment.

5. Although we found little prewinter mortality associated with these conditions, mortality was much greater post-winter for individuals in long, warm prewinter treatments and the dry mass of adults that did survive these conditions was lower, highlighting the need to understand chronic or delayed effects of stress on fitness.

6. Ultimately, we found substantial fitness consequences of prewinter conditions for a diapausing insect. Given that climate change will make these prewinter periods both longer and more intense, it will be important to understand how dormant organisms tolerate or reduce the length of these dormant, inactive periods.

The main data set also contains information from two additional groups, a second population of Pieris napi from Stockholm and Pieris rapae from Kronängen (the same site as the studied Pieris napi population); however, larval rearing of these populations went very poorly so initial sample sizes were much smaller and extremely few individuals survived the experiment. Thus, data from these other groups have not been analyzed.

As a side effect of how random, balanced assignment of pupae to treatments was performed, there are also a substantial number of blank cells associated with ID numbers to which a pupa was never actually assigned. These can be removed before analysis.

See methods in associated paper for more details.

See readme files for more information about each file. .exp files from Sable Systems expdata can be made available upon request.

PrewinterDiapauseIndividual

Main data file with survival and mass change data from the full experiment

PrewinterDiapauseMetabolismMeasurements

File with data from the repeated metabolism measurements on a subset of treatments in the main experiment. Available as both .xlsx and .csv

PrewinterDiapauseManuScript

R script for producing the statistics and figures from the manuscript.