Thermal Variability Modulates Altitudinal Differences in Metabolic Plasticity of the Asiatic Toad.

Area of Science:

• Physiology
• Ecology
• Evolutionary Biology

Background:

• Physiological plasticity is vital for survival in changing environments.
• The climate variability hypothesis (CVH) suggests plasticity correlates with climate variation, but its universality is debated.
• The impact of prior thermal history on plasticity is understudied.

Purpose of the Study:

• To investigate how altitude and thermal variation influence phenotypic plasticity in resting metabolic rate (RMR) and maximum metabolic rate (MMR) of Asiatic toads (Bufo gargarizans).
• To test the CVH and explore the role of thermal history in metabolic plasticity.

Main Methods:

• Studied Asiatic toads across altitudinal gradients.
• Measured RMR and MMR under varying thermal conditions.
• Assessed metabolic substrate choice based on thermal acclimation history.

Main Results:

• RMR plasticity varied with altitude, decreasing in high-altitude toads, contrary to CVH predictions.
• MMR plasticity did not show altitudinal variation but was influenced by warm acclimation, increasing thermal sensitivity.
• Metabolic substrate use was dependent on prior thermal experience.

Conclusions:

• RMR plasticity, not MMR plasticity, appears key for altitudinal adaptation in Asiatic toads.
• Increased thermal fluctuations might impair adaptive RMR plasticity.
• Findings offer insights into macrophysiological responses to global warming.