Are some weeds sleeping? Some concepts and reasons

Groves, R. H. (2006). Are some weeds sleeping? Some concepts and reasons. Euphytica, 148(1-2), 111-120. PDF.

Summary

Not all introduced species become invasive due to biotic and abiotic factors (e.g., lack of genetic diversity, lack of climatic suitability) limiting their expansion. It is also commonly assumed that if an introduced species remains at a low population for a long period of time, it is unlikely to become invasive. Contrary to this assumption, Groves (2006) provides three case studies of invasive plant species which illustrate otherwise. In each of these case studies, the species persisted at low levels for several decades (>50 years) and then rapidly expanded. The author defines species exhibiting this two-phase growth as ‘sleeper’ species. Under future climate change, sleepers may create a new wave of invasions as abiotic constraints become relaxed (e.g., milder winters) for some naturalized species. Therefore, it is important to reassess the current pool of naturalized species  to identify ‘sleeper’ species for eradication in the early, manageable stages of the invasion process.

Take home points

  • Introduced species that remain benign for several decades due to abiotic and biotic constraints can suddenly ‘awaken’ to become invasive. Species that exhibit this two-phase growth are termed ‘sleeper’ species.

  • Under future climate warming, we anticipate limitations for some naturalized species to be lifted, resulting in a new wave of invasive species.

Management implications

  • Invasive species management is most effective in the early stages of an invasion when distributions and population sizes are small. Therefore, the identification and management of sleeper species prior to their rapid expansion allows for feasible, cost-effective management of invaders.

  • Sleeper species are often identified retroactively. Collecting information on the traits, potential impacts, and native range habitat of naturalized species could improve our ability to proactively identify and eradicate sleeper species.

Keywords

Shifting Seasons; Climate Extremes; Competitiveness; Observation; Invasive Plant; Terrestrial Habitat; Risk Assessment