Winter chilling speeds spring development of temperate butterflies

Area of Science:

• Ecology
• Climate Change Biology
• Entomology

Background:

• Phenology, the study of cyclic and seasonal natural phenomena, is crucial for understanding climate change impacts.
• Most insect spring phenology studies focus solely on spring temperatures, neglecting other critical climate factors.
• Citizen science data offers valuable insights into ecological patterns and climate change effects.

Purpose of the Study:

• To investigate the combined effects of spring temperatures and winter cold duration on butterfly spring emergence.
• To disentangle the influence of various climate variables on the phenology of overwintering butterfly species.
• To assess how recent climate change trends, particularly shorter winters, are affecting butterfly emergence timing.

Main Methods:

• Utilized citizen-collected butterfly observation data from the UK (1976-2013) and Sweden (2001-2013).
• Employed spatial mixed models to analyze the impact of climate variables on spring emergence for multiple butterfly species.
• Incorporated experimental pupal development data for one species (Anthocharis cardamines) to model phenology.

Main Results:

• Warmer springs consistently led to earlier butterfly emergence across all studied species.
• Milder winters significantly delayed spring emergence in three out of five UK butterfly species.
• The delaying effect of warmer winters became more pronounced in the last decade, correlating with shorter winter durations.
• Winter duration variations showed a more substantial impact on emergence timing in the UK compared to Sweden.

Conclusions:

• Both spring temperature and winter cold duration are critical drivers of butterfly spring phenology.
• Shortened winters, a consequence of climate change, can lead to significant delays in butterfly emergence, particularly in regions with mild winters.
• These findings highlight the importance of winter conditions for ectothermic animals' responses to climate change and suggest potential impacts at higher latitudes.