Genetic divergence among threespine stickleback that differ in nuptial coloration

Area of Science:

• Evolutionary Biology
• Population Genetics
• Ecology

Background:

• Sexual signals evolve under selective pressures from receivers and the environment.
• Environmental heterogeneity can drive signal divergence, but gene flow dynamics remain unclear.
• Threespine stickleback (Gasterosteus aculeatus) exhibit recent phenotypic divergence in signaling traits.

Purpose of the Study:

• To quantify gene flow between red and black color morphs of threespine stickleback.
• To characterize genetic variation within and among morphs in Oregon and Washington.
• To investigate the spatial scales and barriers influencing genetic divergence.

Main Methods:

• Genetic analysis of red and black stickleback morphs.
• Assessment of within-species and among-morph genetic variation.
• Testing for gene flow levels between distinct color morphs across different populations.

Main Results:

• Black stickleback populations are genetically distinct from nearby red populations.
• The black morph shows evidence of independent evolution at least twice in the study region.
• A unique, genetically and morphologically distinct stickleback group was identified in Connor Creek.

Conclusions:

• Recent divergence in signaling phenotypes does not fully restrict gene flow between red and black morphs.
• Independent evolution of the black morph suggests multiple origins or strong local selection.
• Further research is needed to understand the role of various barriers in shaping genetic and phenotypic patterns.