Physiology Evolves Convergently but Lags Behind Warming in Cities

Area of Science:

• Evolutionary Biology
• Urban Ecology
• Climate Change Biology

Background:

• Urban heat islands (UHIs) create unique environments for studying contemporary evolution.
• Understanding species' adaptive responses to rapid climate change is critical.

Purpose of the Study:

• To quantify the repeatability of evolutionary shifts in thermal tolerance and body size in response to UHIs.
• To assess the role of temperature in driving trait divergence and identify potential adaptational lags.

Main Methods:

• Comparative analysis of urban and non-urban populations across diverse species lineages.
• Quantification of trait divergence (heat tolerance, cold tolerance, body size) in relation to UHI intensity.
• Assessment of adaptational lags by comparing trait shifts to environmental warming.

Main Results:

• Urban populations showed significant increases in heat tolerance and decreases in cold tolerance.
• Trait divergence was positively correlated with UHI intensity, indicating temperature's strong influence.
• Adaptive responses lagged behind warming, with heat tolerance showing a deficit of 0.84°C per 1°C warming.
• Aquatic species exhibited a trend toward smaller body size in urban habitats.

Conclusions:

• Cities serve as valuable experimental systems for investigating the repeatability of evolution.
• Adaptational lags exist, suggesting limits to evolutionary rates in the face of rapid climate change.
• Urban ecosystems can be utilized as forecasting tools to predict species' responses to future warming.