Does the most popular consumer strategy, parasitism, matter to food webs?
Parasitism is the most common animal lifestyle, yet food webs rarely include parasites. The few earlier studies have indicated that including parasites leads to obvious increases in species richness, number of links, and food chain length. A less obvious result was that adding parasites slightly reduced connectance, a key metric considered to affect food web stability. However, reported reductions in connectance following the addition of parasites resulted from an inappropriate calculation. According to USGS researcher Kevin Lafferty and colleagues, two alternative corrective approaches applied to four published studies yields an opposite result — parasites increase connectance, sometimes dramatically. In addition, this study finds that parasites can greatly affect other food web statistics such as nestedness, chain length, and linkage density. Further, while most food webs find that the top levels are least vulnerable to natural enemies, the inclusion of parasites revealed that mid,
