Development and phenotypic correlations: the evolution of tooth shape in Sorex araneus

Area of Science:

• Evolutionary biology
• Developmental biology
• Quantitative genetics

Background:

• Phenotypic covariation, represented by variance-covariance (P) matrices, is shaped by underlying developmental processes.
• Understanding the evolution of these P matrices over microevolutionary timescales is crucial for evolutionary studies.

Purpose of the Study:

• To investigate whether morphogenetic processes drive common patterns of phenotypic covariation in molar shape.
• To assess the evolution of molar shape P matrices in five populations of the common shrew (Sorex araneus) over microevolutionary timescales.

Main Methods:

• Matrix correlation, matrix disparity, and common principal component analysis (CPCA) were employed to analyze P matrix evolution.
• A computer model estimated theoretical covariance introduced by developmental interactions.
• Rarefaction analysis assessed the impact of sample size on P matrix comparisons.

Main Results:

• Significant but small changes in covariance structure were observed among shrew populations.
• Developmental processes explained a relatively small proportion of the observed molar shape covariance.
• Developmental principal components (PCs) were infrequently associated with common principal components (CPCs).
• Sample size critically affected P matrix comparisons, with different thresholds for matrix correlation/disparity and CPCA.

Conclusions:

• Molar shape P matrices evolve rapidly and are only loosely constrained by development.
• Factors more proximate than development likely dominate the shared covariance of molar shape.
• Akaike Information Criterion (AIC) demonstrated better performance than jump-up for CPCA evaluation at smaller sample sizes (n < 30).