Body size decline during thermal evolution is only detected at mild temperature.

Area of Science:

• Evolutionary Biology
• Climate Change Biology
• Physiological Ecology

Background:

• Body size is a critical trait influencing an organism's physiology, metabolism, and reproductive success.
• Previous studies suggest a trend of decreasing body size with rising temperatures, but evidence remains inconsistent.
• Understanding body size evolution under climate warming is crucial for predicting species' responses.

Purpose of the Study:

• To investigate the evolution of body size in experimentally evolved Drosophila subobscura populations under a warming environment.
• To assess the influence of geographical origin and environmental conditions on body size changes.
• To explore the complex interactions between genotype and environment in shaping body size evolution.

Main Methods:

• Experimentally evolved Drosophila subobscura populations from two distinct geographical origins were used.
• Populations were tested in both ancestral (control) and warming environments.
• Body size was measured as a key morphological trait to assess evolutionary responses.

Main Results:

• A decrease in body size was observed in warming-selected populations, but this effect was specific to lower-latitude populations.
• The body size decrease was only evident when these populations were tested in the ancestral (control) environment.
• No significant body size response was detected in the warming environment, potentially due to a balance between thermodynamic stability and selection for reproductive output.

Conclusions:

• Body size evolution under climate warming is complex and involves significant genotype-by-environment interactions.
• The observed inconsistencies across studies may be explained by these complex interactions and variations in experimental setups.
• Predicting body size evolution requires consideration of both intra- and inter-specific variations and their interplay with environmental factors.