How you seek is what you find
To understand how feeding interactions are structured, researchers from Finland and Canada chose to focus on one of the simplest food webs on Earth: the moths and butterflies of Northeast Greenland, as attacked by their specialist enemies, parasitic wasps and flies developing on their prey (called host), killing it in the process.
"What we found in this system was mind-boggling", explains Helena Wirta, the lead author of the study. "When we supplemented the traditional technique of rearing host larvae until the emergence of either the adult or its enemy with modern molecular techniques, every measure of food web structure changed. All of a sudden, we found three times as many interactions between species as before. On average, most types of predator proved less specialized than assumed, and most types of prey were attacked by many more predators than we had thought. Thus, the full web was simply more tightly knit than we initially believed."
"To understand just how much the method affected our perception of our single target web, we may compare variation among different techniques to variation among food webs previously described for different parts of the world", explains Tomas Roslin, who initiated the work. "Web structure simply varied manifold more among our different techniques than among localities from the UK to Japan. Thus, whatever we think that we know about food web structure across the globe may be dictated as much by how we have searched as by how species really interact."
The revealing inner of a bug
What allowed the researchers to dissect the food web with a new precision was the use of DNA barcodes.
"The basis of this approach is to identify species based on variation in a given gene", says Sean Prosser, who spent months in the lab fine-tuning the approach. "By targeting gene regions which differ between the predator and the p
|Contact: Tomas Roslin|
University of Helsinki