Fine-scale behavioural differences distinguish resource use by ecomorphs in a closed ecosystem.

Area of Science:

• Ecology
• Evolutionary Biology
• Animal Behavior

Background:

• Understanding behavioral divergence is key to ecological diversity.
• Arctic charr exhibit distinct ecomorphs with presumed habitat and foraging differences.

Purpose of the Study:

• Investigate the role of behavior in resource use divergence between two Arctic charr ecomorphs.
• Analyze annual habitat use and foraging specialisms.

Main Methods:

• Biotelemetry and stable isotope analysis (δC13) were employed.
• Compared spatial-temporal habitat use and diet between pelagic and littoral morphs.

Main Results:

• Pelagic morph charr showed greater δC13 depletion (zooplanktivory) than the littoral morph.
• Littoral morphs utilized habitat more than pelagic morphs, with significant differences in depth and activity.
• Habitat use patterns varied seasonally, particularly during autumn spawning and ice break.

Conclusions:

• Extensive habitat overlap but fine-scale differences suggest competition is crucial for maintaining Arctic charr polymorphism.
• Behavioral divergence may promote reproductive isolation and sympatric evolution.