Plasticity cannot fully compensate evolutionary differences in heat tolerance across fish species

Area of Science:

• Ecology
• Evolutionary Biology
• Climate Change Biology

Background:

• Predicting species' responses to climate warming requires understanding thermal tolerance variation.
• Both evolutionary adaptation and phenotypic plasticity influence organismal heat tolerance.

Purpose of the Study:

• To quantify the relative contributions of evolution and phenotypic plasticity to variation in fish heat tolerance.
• To assess the capacity of fish to acclimate to rising environmental temperatures.

Main Methods:

• Analysis of 272 thermal death time curves from 53 fish species.
• Quantification of evolutionary and plastic contributions to heat tolerance variation.
• Validation of estimates using critical temperatures under ramping conditions.

Main Results:

• Evolution accounts for 80.5% of variation in heat tolerance elevation, while plasticity accounts for 12.4%.
• Heat tolerance increases by 0.54°C (evolutionary) and 0.32°C (plastic) per 1°C rise in environmental temperature.
• Fish populations exhibit limited capacity to acclimate to warming waters.

Conclusions:

• Evolutionary adaptation is the primary driver of heat tolerance differences among fish species.
• Phenotypic plasticity offers only partial amelioration of warming impacts.
• Accelerating warming may outpace the adaptive capacity of fish through acclimation, increasing vulnerability.