Balancing selection shapes density-dependent foraging behaviour.

Area of Science:

• Neuroethology
• Evolutionary Genetics
• Chemical Ecology

Background:

• Optimal foraging strategies are influenced by social competition and behavioral tactics.
• The genetic and neural mechanisms integrating social cues into foraging decisions remain largely unexplored.

Purpose of the Study:

• To investigate how ascaroside pheromones, signaling population density, affect foraging behavior in Caenorhabditis elegans.
• To identify the genes and neural circuits involved in sensing social information and modulating foraging decisions.

Main Methods:

• Utilized quantitative trait locus (QTL) mapping to identify genetic loci associated with pheromone sensitivity.
• Investigated the role of the G-protein-coupled receptor gene srx-43 in ASI sensory neurons.
• Analyzed the impact of natural variation in ascaroside secretion and detection on foraging strategies and competitive growth.

Main Results:

• Ascaroside pheromones, specifically icas#9, were found to suppress exploratory foraging in C. elegans.
• Natural isolates exhibit varying sensitivities to icas#9, linked to heritable alternative foraging strategies.
• The srx-43 gene, encoding an ascaroside receptor in ASI neurons, was identified as a key regulator of this density-dependent suppression of exploration.
• Two ancient srx-43 haplotypes confer competitive advantages dependent on ascaroside signaling and food availability.

Conclusions:

• Heritable variation in ascaroside sensitivity, mediated by srx-43, generates alternative density-dependent foraging behaviors in C. elegans.
• Balancing selection at the srx-43 locus supports these alternative strategies, aligning with predictions from foraging game theory.