Monday, January 12, 2009

Who is Naïve, the invaders or the natives?
Why some species can invade natural ecosystems and many others cannot, is a question that doesn’t have an answer. Many ideas have been proposed to explain this, with relative success, but very low predictability. Most of the ideas have been focused on the factors that promote invasion (i.e. why successful invaders are successful). In a recent ideas paper Koen Verhoeven and collaborators propose a different approach. They ask the question, how ecological mismatches between natives and exotics can explain invasion? They propose a series of predictions based on plant defenses and plant enemies (herbivores, pathogens). They propose that the mismatches between exotic plants and their new enemies could explain their success or failure. For example, if a plant presents a new type of toxic chemical compound that the local herbivores have never encounter and cannot deal with, it would be a clear advantage for the plant (this is related to the novel weapons idea). On the other hand, if the plant has defenses that need to be trigger by a particular enemy (for example an induced defense triggered by a specific chewing insect) that could be a disadvantage for it. They propose that biotic resistance (when the native community resist the invasion) and enemy release (when an exotic invades due to experiencing less pressure by enemies than in its native range) are not oppose ideas but could be the different outcome of these mismatches.

This paper propose a very interesting approach to study some cases of successful and failed invasions, and I look forward for empirical tests of this idea.

Koen J. F. Verhoeven, Arjen Biere, Jeffrey A. Harvey, Wim H. van der Putten (2009). Plant invaders and their novel natural enemies: who is naïve? Ecology Letters, 12 (2), 107-117 DOI: 10.1111/j.1461-0248.2008.01248.x

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