Regional thermal variation in a coral reef fish

Area of Science:

• Marine biology
• Climate change adaptation
• Evolutionary biology

Background:

• Species' climate change responses depend on population-level adaptation.
• Intraspecific variation, driven by genetics and plasticity, influences thermal performance curves.
• Marine intraspecific variation is understudied due to perceived high dispersal rates.

Purpose of the Study:

• To investigate intraspecific variation in coral reef damselfish (Acanthochromis polyacanthus) across latitudes.
• To determine if populations exhibit co-gradient variation in aerobic physiology along a thermal gradient.

Main Methods:

• Examined aerobic physiology across a thermal gradient (27-31.5°C) representing current and future ocean temperatures.
• Compared immunocompetence, haematocrit, and anaerobic enzyme activity between low- and high-latitude populations.
• Assessed co-gradient variation in relation to thermal sensitivity.

Main Results:

• Intraspecific variation in aerobic physiology was found between low- and high-latitude damselfish populations.
• Co-gradient variation was observed across the thermal gradient.
• No significant differences were detected in immunocompetence, haematocrit, or anaerobic enzyme activity between latitudes.

Conclusions:

• Dispersal limitations in marine environments can facilitate local adaptive responses.
• Intraspecific variation may not be consistent across all traits.
• Identifying locally adapted traits is crucial for predicting species' responses to climate change and assessing adaptive capacity.