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17 Genetically Modified Organisms
as Invasive Species?
Rosie Hails and Tracey Timms-Wilson
17.1 Introduction
The release of genetically modified organisms (GMOs) is a controversial
subject. Some perceive it to be the single most important development in
biology since the discovery of natural selection. Others are concerned that
the movement of genes with no reference to natural species boundaries
could pose new ecological risks. One conjectural risk is that transgenes will
either cause the host species to become invasive or they will escape from the
original host species and cause other species to become invasive. Gene flow
between species occurs naturally, although the frequency varies within and
across kingdoms. Such gene flow is responsible for creating new combinations
of genes, with the potential for introgression or speciation. Hybridisation
has been proposed as a stimulus for the evolution of invasiveness in
plants (Ellstrand and Schierenbeck 2000), suggesting that new combinations
can create genotypes with different, and perhaps surprising ecological
behaviours. Do transgenes pose particular risks in this respect? Is it possible
to predict the probability that transgenes will cause invasiveness in recipient
organisms?
17.2 Quantitative Measures of Invasion Risk
To answer this question, we present a quantitative framework for the estimation
of the probability of invasiveness. The risk assessment of genetically
modified organisms has adapted approaches developed for pesticides and
other potentially toxic substances in the environment. In its simplest form,
quantifying risk involves estimating the expression of toxicity and the likeli-
Ecological Studies,Vol. 193
W. Nentwig (Ed.)
Biological Invasions
© Springer-Verlag Berlin Heidelberg 2007