Measuring American black bear genetic load in fixed structural variants and runs of homozygosity

The isolated Saugeen Peninsula population of Ursus americanus shows reduced nucleotide diversity and elevated runs of homozygosity and structural variant abundance versus mainland Ontario populations.

• Why it matters: Geographic isolation can reduce gene flow and increase drift and inbreeding, potentially reshaping genetic load and the distribution of structural variants in conservation-relevant populations.
• What they did: Using short-read and long-read sequencing, the study compared five Ontario bear populations with metrics including nucleotide diversity (pi), Tajima’s D, ROH, and genome-wide SVs to detect isolation signatures.
• The result: The Saugeen Peninsula bears also had elevated genetic load across genomic features, implying greater exposure of deleterious variation expressed in ROH and population-specific SVs.

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