5 research outputs found
Can the enemy release hypothesis explain the success of invasive alien predators and parasitoids?
Biological invasions are ecologically and economically costly. Understanding the major
mechanisms that contribute to an alien species becoming invasive is seen as essential for limiting the
effects of invasive alien species. However, there are a number of fundamental questions that need
addressing such as why some communities are more vulnerable to invasion than others and, indeed,
why some alien species become widespread and abundant. The enemy release hypothesis (ERH) is
widely evoked to explain the establishment and proliferation of an alien species. ERH predicts that an
alien species introduced to a new region should experience a decrease in regulation by natural enemies
which will lead to an increase in the distribution and abundance of the alien species. At the centre of
this theory is the assumption that natural enemies are important regulators of populations.
Additionally, the theory implies that such natural enemies have a stronger regulatory effect on native
species than they do on alien species in the introduced range, and this disparity in enemy regulation
results in increased population growth of the alien species. However, empirical evidence for the role of
the ERH in invasion success is lacking, particularly for invertebrates. Many studies equate a reduction
in the number of natural enemies associated with an alien species to release without studying
population effects. Further insight is required in relation to the effects of specific natural enemies on
alien and native species (particularly their ability to regulate populations). We review the role of
ecological models in exploring ERH. We suggest that recent developments in molecular technologies
offer considerable promise for investigating ERH in a community context