The biology hidden inside residual within-individual phenotypic variation

Area of Science:

• Evolutionary Biology
• Quantitative Genetics
• Phenotypic Plasticity

Background:

• Phenotypic variation is hierarchically structured across taxa, populations, genotypes, and individuals.
• Within-individual variation, particularly in labile traits like behavior and physiology, has been less emphasized than variation among individuals.
• This hierarchical structure presents challenges for defining biological phenomena and developing consistent explanatory frameworks.

Purpose of the Study:

• To explore consequences of the hierarchical structure of phenotypic variation using a heuristic statistical model.
• To highlight the significance of within-individual variance and its contributing factors.
• To investigate how interactions across hierarchical levels influence the evolution of plasticity and stability.

Main Methods:

• Statistical partitioning of phenotypic variance.
• Development of a heuristic statistical model to analyze variance components.
• Examination of residual within-individual variation and its relationship to environmental factors and fitness.

Main Results:

• Within-individual variance arises from labile phenotypes exhibiting plasticity or deviations from a norm-of-reaction.
• Factors influencing within-individual variance include environmental interactions, ecological effects on plasticity, and adaptive variance.
• Interactions across hierarchical levels are preconditions for the evolution of plasticity, extending to within-individual adaptive plasticity and canalization.

Conclusions:

• A framework for analyzing phenotypic variance variation reveals novel insights into the evolution of plasticity.
• Residual within-individual variation can be subject to adaptive plasticity and canalization-like processes.
• Emerging statistical tools enable new research questions linking phenotype, environment, and evolutionary processes at the within-individual level.