Can Hormesis Facilitate Biological Invasions?

ABSTRACT

During biological invasions, introduced organisms are exposed to multiple, sequential environmental stressors across invasion stages. Although stress is traditionally viewed as a source of damage and environmental filtering, exposure within a hormetic zone may induce a persistent state that improves performance under subsequent challenges. Here, we critically review the available evidence for stress‐induced hormesis in invasion‐relevant contexts. We then develop a four‐stage framework linking hormetic exposure to persistent state changes, improved performance under subsequent stress, and ultimately increased establishment. Importantly, the framework posits that stress‐induced hormesis can facilitate invasions when its effects are maintained across all four stages and ultimately translated into demographic outcomes. Building on this framework, we propose the Hormesis‐Enhanced Propagule Quality Hypothesis, which defines propagule quality as a dynamic, stress‐responsive property. The hypothesis emphasizes that hormetic effects on fitness‐related traits can enhance establishment success, particularly when populations are near demographic or Allee‐effect thresholds. When retained across generations, these effects may stabilize founder lineages during vulnerable early population growth and increase colonization yield. However, hormetic responses are inherently context‐, endpoint‐, and time‐dependent, may involve endpoint‐specific trade‐offs or cross‐susceptibility, and may provide diminished or no benefit under environmental mismatch. We therefore outline research priorities for determining when transient stress responses scale to population‐ and community‐level invasion outcomes. These priorities include sequential‐stress experiments, multigenerational lineage tracking, multi‐omics, and demographic modeling. The four‐stage framework and hypothesis advance invasion theory by identifying stress‐modified propagule quality as a previously overlooked determinant of establishment success, with potential implications for predicting and managing invasive species.