Nonparallel genome changes within subpopulations over time contributed to genetic diversity within the US Holstein...

Area of Science:

• Animal Genetics
• Population Genetics
• Genomic Selection

Background:

• Maintaining genetic variation within a population is crucial for sustained genetic gain and adaptability.
• Subpopulations within a breed can serve as a valuable resource for preserving genetic diversity.

Purpose of the Study:

• To stratify a population into distinct subpopulations using genomic data.
• To analyze the genomic trajectories and allele frequency changes within these subpopulations.
• To investigate the potential for optimizing selection decisions by understanding population structure.

Main Methods:

• K-means clustering applied to a genomic relationship matrix of 20,990 animals using 58,990 SNP markers to identify 5 subpopulations.
• Pedigree tracing to identify 5 families and analyze allele frequency changes over 10 generations.
• Estimation of cluster-specific SNP effects for traits like stature.

Main Results:

• Successful stratification into 5 genetically distinct clusters (C1-C5) with higher inbreeding within clusters.
• Significant population differentiation (average fixation index of 0.03) not solely due to genetic drift.
• Analysis revealed varied genomic trajectories, including selective sweeps and differing allele frequency changes across families.
• Replicate frequency spectrum indicated distinct population changes, with varying proportions of markers reversing allele frequency direction.

Conclusions:

• The study successfully stratified a population into genetically differentiated subpopulations, highlighting unique evolutionary paths.
• Observed allele frequency changes and genomic trajectories provide insights into population dynamics.
• Further research is needed to apply these findings for optimizing diversity and selection strategies in animal breeding.