High-Arctic butterflies become smaller with rising temperatures

Area of Science:

• Ecology
• Climate Change Biology
• Zoology

Background:

• Increasing global temperatures due to climate change impact ectotherm physiology.
• Body size responses to temperature vary, with potential for both reduction (metabolic cost) and increase (longer growing seasons).
• Understanding these responses is crucial for predicting species' vulnerability to climate change, especially in sensitive Arctic ecosystems.

Purpose of the Study:

• To investigate the long-term effects of climate warming on the body size of two High-Arctic butterfly species.
• To establish the longest known time series data on body size variation in these Arctic insects.
• To determine the relationship between summer temperature and butterfly body size.

Main Methods:

• Analysis of a long-term dataset (1996-2013) of wing length measurements from nearly 4500 individuals of Boloria chariclea and Colias hecla.
• Annual sampling in Zackenberg, Greenland, a High-Arctic location.
• Statistical analysis correlating wing length with summer temperature data.

Main Results:

• A significant decrease in wing length was observed in both Boloria chariclea and Colias hecla over the study period.
• The rate of body size decrease was similar between the two species.
• Warmer summer temperatures were identified as the primary driver for the observed reduction in wing length.

Conclusions:

• High-Arctic butterflies are exhibiting a consistent negative response in body size to increasing summer temperatures.
• Reduced body size can negatively affect critical life-history traits such as dispersal and fecundity.
• These findings highlight potential severe challenges for Arctic butterfly populations facing rapid climate change.