Genetically Distinct Behavioral Modules Underlie Natural Variation in Thermal Performance Curves

Area of Science:

• Evolutionary Biology
• Genetics
• Animal Behavior

Background:

• Organismal traits often exhibit thermal reaction norms, which are predictable responses to temperature.
• Locomotory behavior in animals is highly plastic and sensitive to environmental temperature, posing challenges for genetic analysis.
• Understanding the genetic basis of behavioral plasticity is crucial for evolutionary studies.

Purpose of the Study:

• To characterize behavioral reaction norms as thermal performance curves in *Caenorhabditis briggsae*.
• To quantify the genetic and plastic variation in locomotory behavior in response to temperature.
• To identify the genomic architecture underlying thermal behavioral responses.

Main Methods:

• Utilized 23 wild isolate genotypes and 153 recombinant inbred lines of *Caenorhabditis briggsae*.
• Applied a function-valued trait framework to analyze multivariate phenotypic responses.
• Performed quantitative trait locus (QTL) mapping to identify genetic regions influencing behavior.

Main Results:

• Identified genetically distinct behavioral modules contributing to overall thermal performance curves.
• QTL mapping revealed significant loci on Chromosome II for activity at benign temperatures.
• Loci on Chromosome V were associated with high-temperature sensitivity, with individual QTL explaining up to 28% of variation.

Conclusions:

• Behavioral responses to temperature can evolve through independent modifications of genetically distinct modules.
• This modularity provides a framework for understanding the evolution of complex thermal performance curves.
• The study elucidates the genetic architecture of behavioral plasticity in response to environmental temperature.