EICA hypothesis information

The evolution of increased competitive ability (EICA) hypothesis was first proposed by Bernd Blossey and Rolf Nötzold in 1995 as a way to explain the success of invasive, non-indigenous species (in particular, plants). Observing that:

1. there is usually a lag period between the time of introduction of an invasive species and the point at which it is considered invasive, and
2. invasive plants seem to be more virulent in habitats into which they have been introduced (as compared to their native habitats), the scientists presumed a sort of naturalization through modification for non-indigenous plants.

Because of a lack of native predation, the scientists reasoned, introduced plants are able to reallocate resources from defense mechanisms into growth and development. Introduced plants can thereby evolve to grow taller, produce more biomass, and yield more viable offspring than their native counterparts, according to the hypothesis.^[1]

Blossey and Nötzold tested their hypothesis on Lythrum salicaria (purple loosetrife) by potting seeds from plants growing in Ithaca, New York, U.S., and Lucelle, Switzerland. The seeds were allowed to germinate in a lab at Christian-Albrechts University in Kiel, northern Germany, and observed for two years. True to the predictions of the EICA Hypothesis, the plants derived from Ithaca produced significantly more biomass that the plants derived from Lucelle. The Lythrum salicaria plants derived from Ithaca also grew taller and were significantly less resistant to the root-feeding weevil present over its native range.