HIERARCHICAL ANALYSIS OF INBREEDING DEPRESSION IN PEROMYSCUS POLIONOTUS

Area of Science:

• Evolutionary Biology
• Population Genetics
• Animal Reproduction

Background:

• Inbreeding depression severity varies across species, with limited understanding of factors predicting sensitivity.
• Understanding heterogeneity in inbreeding depression is crucial for conservation and evolutionary studies.

Purpose of the Study:

• To investigate the causes of variation in inbreeding depression effects on reproduction, survival, and growth.
• To determine if subspecies-specific traits or random genetic factors influence inbreeding depression responses.

Main Methods:

• Experimental inbreeding was applied to three subspecies of Peromyscus polionotus mice across three replicate stocks each.
• Effects of inbreeding on dam's reproduction and litter's growth, viability, and mass were quantified.
• Variation in responses was analyzed in relation to subspecies characteristics and random founder effects.

Main Results:

• Inbreeding negatively impacted dam's breeding probability, litter size, and litter viability.
• Inbreeding increased within-litter variance in mass and reduced mass at weaning.
• All observed variation in inbreeding depression responses was attributed to random founder effects, not subspecies differences.

Conclusions:

• Inbreeding depression is driven by the unequal partitioning of deleterious alleles among founders, with few alleles having major effects on specific fitness components.
• Random drift and selection during bottlenecks can cause divergence in genetic loads among natural populations.
• The universality of inbreeding depression may be maintained by different alleles affecting different fitness traits across diverse environments.