Infectious food webs.

Food webs, descriptions of who is eating whom in an ecosystem, are one of the most enduring and influential concepts in ecology. An increasing number of studies are including parasite-host feeding interactions in food webs, each providing evidence that parasites alter our perception of food web structure. Amundsen et al. in this issue report intriguing details on the role of parasites in the complexity of an arctic food web. They highlight the role of links generated by trophically transmitted parasites - those transmitted via a predator-prey interaction between two hosts. These data show the type of natural history knowledge necessary to advance our understanding of food web complexity, structure and dynamics.