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