Hybrid vigor

Definition

The superior performance of hybrid offspring relative to their parental lines, manifesting as enhanced fitness, growth, fecundity, or stress tolerance that exceeds the mid-parent mean or even the best parent. In arthropods, hybrid vigor often appears in crosses between geographically isolated populations or between inbred laboratory strains, producing offspring with greater survival, faster development, or higher reproductive output than either parental stock. The effect typically diminishes in subsequent generations as recombination breaks up favorable gene combinations.

Etymology

Example

Crossing two inbred lines of the silkworm Bombyx mori frequently restores egg viability and larval growth rates that had declined due to inbreeding depression, demonstrating classic hybrid vigor exploited in sericulture.

Synonyms

• Heterosis
• outbreeding enhancement

Related Terms

• inbreeding depression
• hybrid zone
• heterozygote advantage
• F1 hybrid
• outbreeding depression
• genetic load

Usage Notes

Specialists prefer 'heterosis' in formal genetic literature; 'hybrid vigor' is common in applied contexts such as apiculture, sericulture, and biocontrol agent rearing. The effect is most pronounced in F1 hybrids and requires genetic divergence between parents—too distant a cross may yield outbreeding depression instead. Not all traits show heterosis; some may display intermediate inheritance or dominance of deleterious alleles.