EFFECT OF AN EXPERIMENTAL BOTTLENECK ON MORPHOLOGICAL INTEGRATION IN THE HOUSEFLY

Area of Science:

• Evolutionary genetics
• Quantitative genetics
• Population genetics

Background:

• Genetic integration, the degree to which variation in different traits is genetically linked, is crucial for understanding evolutionary processes.
• Population bottlenecks, periods of reduced population size, can significantly impact genetic variation and covariation among traits.

Purpose of the Study:

• To investigate the effects of different population bottleneck sizes on the genetic integration of morphological traits in the housefly (Musca domestica L.).
• To determine how bottleneck size influences additive genetic covariance and correlation matrices.

Main Methods:

• Derived three measures of multivariate integration from additive genetic covariance and correlation matrices.
• Estimated matrices from parent-offspring covariances in bottleneck lines (initiated with 1, 4, or 16 pairs) and a control population.
• Analyzed trait interrelationships using principal component analysis.

Main Results:

• Intermediate-sized bottlenecks (4 or 16 pairs) significantly increased average genetic correlation among traits, leading to nearly isomorphic variation.
• Single-pair bottlenecks significantly disrupted trait interrelationships, abolishing the trait suites observed in the control population.
• Alterations in genetic relationships suggest the presence of nonadditive genetic variation (e.g., epistasis) in the control population.

Conclusions:

• Population bottleneck size critically influences the genetic integration of morphological traits.
• Disruption of genetic relationships by bottlenecks highlights the role of nonadditive gene action in evolutionary processes.
• Findings have implications for understanding speciation mechanisms driven by bottlenecks and nonadditive genetic effects.