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The Allee effect as a threshold in invasions

The Allee effect as a threshold in invasions. The Allee effect, most broadly, is when population size influences fitness. Allee et al. 1949 It can be a positive or negative relationship. There can be a threshold level in population size, below which the population declines. Cappuccino 2004.

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The Allee effect as a threshold in invasions

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  1. The Allee effect as a threshold in invasions

  2. The Allee effect, most broadly, is when population size influences fitness. Allee et al. 1949 • It can be a positive or negative relationship. • There can be a threshold level in population size, below which the population declines

  3. Cappuccino 2004

  4. Levine, J.M., et al. 2004. A meta-analysis of biotic resistance to exotic plant invasions. Ecology letters. Quarantine Eradication Containment From Brooke

  5. Cappuccino 2004

  6. Mechanisms • Failure to find mates • Inbreeding depression • Predator satiation • Allelopathy • Different strengths of inter- and intraspecific competition • Stochastic effects on population sizes

  7. Van Dyke 2003

  8. Liebhold and Bascompte, 2003

  9. Liebhold and Bascompte, 2003

  10. Conclusions • Eradication does not need to be 100% • Extinction is stochastic and probabilistic • Timing of eradication efforts is important

  11. How does population structure influence Allee effects on invasive populations. • Metapopulation structure and migration • Migration between invasive populations can increase effective population size • One migrant per generation negates negative effect of inbreeding depression • Rescue effect

  12. Van Dyke 2003

  13. Questions • Is the Allee effect likely to be important or useful for studies of invasive species? • Can studies of rare species preservation be useful in studies of invasive species spread? • How does understanding population structure influence invasion dynamics? • When is there a negative effect of large population size on individual fitness? • Are there other thresholds for invasion success that are not related to population size?

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