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INVASION ECOLOGY…CURIOUSER & CURIOUSER
ALIEN INVASION
vocabulary
indigenous = native to a particular place
biogeographical = the branch of biology that studies the geographical distribution of organisms
The Enemy Release Hypothesis (ERH)
Relates the success of non-indigenous species (NIS) to reduced control by enemies Pathogens Parasites Predators
Studies are split Biogeographical analyses show a reduction in the
diversity of enemies in the introduced range compared with the native range
Community studies imply no significant enemy differences between natives and invasives
Too simple to describe processes at work?
Evolution of Increased Competitive Ability hypothesis(EICA)
Blossey & Nötzold (1995)Observations
Usually a lag period between time of introduction & point at which it is considered invasive
Invasive plants seem to be more virulent in habitats into which they have been introduced (as compared with their native habitats)
Presumed a sort of naturalization through modification
Predicts that much of the invasive potential of an invasive species is derived from its ability to evolve to reallocate its resources
Invasion model
Local adaptation
Phenotypic plasticity
Sp
eci
es
freq
uen
cy
Introduced Naturalized
Lag Invasive
Sexton et al. 2002. Ecological Applications 12:1652-1660.
Plasticity and adaptive evolution can lead to greater invasiveness