Inbreeding Depression in Animal Populations

Inbreeding depression describes the reduction in biological fitness arising when closely related individuals mate. By increasing homozygosity, it exposes deleterious recessive alleles and reduces genetic diversity, undermining survival, growth, reproduction and resilience to environmental change. In animal populations, effects span from elevated embryonic mortality and impaired parental care to diminished disease resistance and altered life-history traits. Severity varies among taxa, sexes and life stages, and may be exacerbated by ecological stressors or mitigated by behavioural or social interactions. Understanding inbreeding depression is essential for conserving small or fragmented populations, managing captive breeding programmes and sustaining agricultural and aquaculture stocks. Recent advances combine demographic analysis, genome-wide markers and meta-analytic synthesis to elucidate the genetic architecture, temporal dynamics and context-dependence of inbreeding effects across diverse species.

Research from Nature Portfolio

Age-stage-specific life table analyses in a model lepidopteran pest have demonstrated that successive generations of full-sibling mating lead to pronounced declines in egg hatchability, juvenile survival and adult fecundity. Inbred lines exhibit lower intrinsic and finite rates of increase and extended generation times compared with outbred controls. The magnitude of depression varies across developmental stages, highlighting windows of heightened vulnerability. This study establishes a quantitative framework for linking demographic parameters to underlying molecular determinants of inbreeding depression and offers a baseline for exploring genomic regions subject to purging or overdominance in managed and wild populations.

Inbreeding Depression in Animal Populations publication trend

The graph below shows the total number of articles in inbreeding depression in animal populations across all publications each year (not limited to Nature Index journals).

Technical terms

Inbreeding depression: Reduced fitness resulting from increased homozygosity when related individuals breed.

Heterozygosity: Proportion of loci at which an individual carries two different alleles, reflecting genetic diversity.

Runs of homozygosity (ROH): Contiguous stretches of the genome that are homozygous, indicating shared ancestry and inbreeding.

Effective population size (Ne): The size of an idealised population that would experience genetic drift or inbreeding at the same rate as the observed population.

Intrinsic rate of increase (r): The per capita rate at which a population grows under optimal conditions, accounting for births and deaths.

Net reproduction rate (R₀): The average number of female offspring produced by a female over her lifetime, indicating population replacement potential.

References

1. Generation-based life table analysis reveals manifold effects of inbreeding on the population fitness in Plutella xylostella. Scientific Reports (2015).
2. Sex‐specific inbreeding depression: A meta‐analysis. Ecology Letters (2022).
3. Temporal and region‐specific variations in genome‐wide inbreeding effects on female size and reproduction traits of rainbow trout. Evolutionary Applications (2021).
4. The effects of inbreeding on disease susceptibility: Gyrodactylus turnbulli infection of guppies, Poecilia reticulata. Experimental Parasitology (2016).