Selection, Linkage, and Population Structure Interact To Shape Genetic Variation Among Threespine Stickleback Genomes

Area of Science:

• Evolutionary biology
• Population genetics
• Genomics

Background:

• Genetic variation patterns are shaped by population structure and genome organization.
• Spatially variable selection between marine and freshwater habitats profoundly impacts threespine stickleback genomes.
• Rapid adaptation (within 50 years) to new environments utilizes standing genetic variation maintained by gene flow.

Purpose of the Study:

• To investigate how linkage to selected loci affects genetic variation across the stickleback genome.
• To understand the interplay between spatially variable selection, population structure, and genomic variation.
• To analyze population genomic data and genetic maps from Cook Inlet, Alaska stickleback.

Main Methods:

• Population genomic data analysis of marine and freshwater stickleback.
• Utilizing dense genetic maps derived from study populations.
• Conducting forward genetic simulations to model selection and population structure effects.

Main Results:

• Divergent selection has opposing effects on linked variation: marine chromosomes near selected loci are depauperate, while freshwater chromosomes are highly diverse.
• Forward genetic simulations confirmed these patterns when selective environments differed in population structure.
• Dense genetic maps revealed that selection and population structure interact to influence large genomic regions.

Conclusions:

• The geographic structuring of populations significantly influences selection outcomes on genetic variation.
• The recombination landscape and linkage play a crucial role in extending the genomic impact of selection.
• These findings enhance understanding of adaptation and evolution in response to environmental heterogeneity.