Dimensionality and Modularity of Adaptive Variation: Divergence in Threespine Stickleback from Diverse Environments

Area of Science:

• Evolutionary biology
• Ecology
• Genetics

Background:

• Environmental conditions drive evolutionary and plastic responses, leading to phenotypic divergence.
• Debate exists on whether divergence is constrained to a single major axis or occurs along multiple axes.
• Threespine stickleback (Gasterosteus aculeatus) populations in different lakes offer a model for studying adaptive radiation.

Purpose of the Study:

• To investigate the dimensionality of phenotypic divergence in threespine stickleback populations across diverse lake environments.
• To determine if divergence is constrained along a single axis or occurs multidimensionally.
• To examine how different functional suites of traits (defensive, swimming, trophic) contribute to divergence.

Main Methods:

• Analysis of phenotypic trait variation in 14 natural populations of threespine stickleback.
• Multivariate statistical methods to assess the dimensionality of mean trait values and trait covariances.
• Comparison of divergence patterns across distinct functional trait suites.

Main Results:

• Populations exhibit high dimensionality of divergence, refuting a history of constraint along a single axis.
• Divergence dimensionality varied among different functional trait suites.
• The integration of trait suites differed significantly between populations, influenced by specific traits.

Conclusions:

• Phenotypic divergence in threespine stickleback is multidimensional, allowing for adaptation across various trait axes.
• Environmental conditions and trait-specific selection influence the dimensionality and integration of adaptive traits.
• This study provides insights into adaptive radiation processes and suggests broader applicability of multidimensional divergence analyses.