Changes in local interaction rules during ontogeny underlie the evolution of collective behavior

Area of Science:

• Behavioral Ecology
• Evolutionary Biology
• Neuroscience

Background:

• Collective motion, crucial for survival, arises from individual interactions.
• Understanding how local interactions change with evolving collective behaviors is key.
• The Mexican tetra (Astyanax mexicanus) offers a unique model with schooling surface and non-schooling cave forms.

Purpose of the Study:

• To investigate how fish modulate swimming in response to neighbors.
• To compare developmental changes in social interaction between schooling and non-schooling populations.
• To understand the evolutionary basis of collective behavior differences.

Main Methods:

• Comparative analysis of Mexican tetra surface and cave forms.
• Observation of individual swimming behavior and neighbor interactions across development.
• Quantification of speed and turning modulations relative to conspecifics.

Main Results:

• Surface fish exhibit a developmental transition towards schooling behavior.
• Alignment to neighbors emerges by 28 days post-fertilization in surface fish.
• Robust attraction, indicative of schooling, develops by 70 days post-fertilization in surface fish.
• Cavefish show no developmental emergence of alignment or attraction to neighbors.

Conclusions:

• Evolutionary divergence has led to distinct local interaction rules between surface and cavefish.
• Developmental changes in response to neighbors are critical for the emergence of schooling.
• Local interaction rules are a key target for the evolution of collective behaviors.