Who has ever heard of the big bad moth?
This paper is really novel and interesting on so many levels. At a basic level, there are some very nice elements developed this paper which make it a top paper. Of course it is no surprise that moths eat lichens, but I had never given it much thought nor seen the word lichenivorous in print. EFS or enemy-free space is a very intriuging concept. The design of the experiment is very clean and direct. At a more conceptual level, the implications of a definitive demonstration of EFS sigificantly furthers ecolutionary ecology. This study very clearly demonstrates the capacity for host-herbivore interactions to act as a selection process which then shapes the coevolution between the herbivore and the plant.
The study ‘Enemy-free space and the host range of a lichenivorous moth: a field experiment’ by Heikki Pöykko in the April 2011 issue of Oikos is a well written, direct, and simple study. The hypothesis tested is that animal species can sometimes selectively choose how they live to avoid or at least reduce predation risk. This is an intutitive hypothesis in that many animals forage optimally based on resource levels and predation risk. However, the application of this hypothesis to moth species is less obvious in many respects and is thus even more important in that it is not as easy to conceive of moths functioning in this capacity. The hypothesis in this paper is then deconstructed into the following 3 critical predictions: herbivore fitness is higher in the absence of enemies, with enemies present the moth fitness is higher on its preferred lichen, and on the preferred lichen with enemies absent fitness is reduced (i.e. coevolution). All three predictions were supported with a set of simple exclosures applied to the lichen and moth larvae added.
Trophic interactions, direct and indirect, can lead to coevolution. Generalist natural enemies can narrow diet breadth (which generates the opportunity for coevolution). Properties such as physical attributes of a plant (like the nurse plant facilitation literature wherein shrubs provide shade), and not just chemical sequestration, can provide the substrate for selection processes.
In summary, this was a very neat paper!
Here are some photos from the author. Click on a thumbnail to view larger image.