Submitted to: Biological Invasions
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/7/2006
Publication Date: N/A
Citation: Interpretive Summary: Factors contributing to the naturalization of invasive plants are important and are currently poorly understood. The so-called Enemy Release Hypothesis says that plants naturalize and spread may do so because they escape insect herbivores that impact other plants. We tested this hypothesis by examining the number of insect herbivores and the amount of their feeding damage on Eugenia species, small trees in the myrtle family. We compared the attack on native, invasive and noninvasive Eugenia species. We found that invasive Eugenia did not experience release in terms of total number of herbivore species, but did in terms of insects with narrow diets and internal feeders. In addition, introduced Eugenia, both invasive and non-invasive, sustained less herbivore damage, especially damage by insects with narrow diets and internal feeding insects, than native Eugenia. This study suggests that escape from natural enemies is unlikely to be the primary reason for the spread of the invasive Eugenia. The study’s three-way comparison of related native, non invasive, and invasive plants is a new and informative approach to better elucidate factors responsible for plant invasion.
Technical Abstract: The enemy release hypothesis (ERH) has been frequently invoked to explain the naturalization and spread of introduced species. In this study, we employed a three-way comparison, in which we compared herbivore faunas and herbivore damage among native, introduced invasive, and introduced non-invasive plants in the genus of Eugenia in south Florida. We found that invasive Eugenia did not experience release in terms of total number of herbivore species, but did in terms of oligophagous and endophagous herbivores. In addition, introduced Eugenia, both invasive and non-invasive, sustained less herbivore damage, especially damage by oligophagous and endophagous insects, than native Eugenia. However, the difference in insect damage between introduced invasive and introduced non-invasive Eugenia is very small, and escape from herbivores is therefore unlikely to account for the spread of invasive Eugenia. We would not have been able to draw this conclusion without inclusion of the non-invasive Eugenia species in the study.