Food webs in motion

In ecology, the movement of individuals across landscapes (dispersal) and the trophic interactions between populations in food webs are typically studied independently. Researchers from Belgium, the Czech Republic, and Switzerland have teamed up to connect these two ecological perennials to infer which dispersal rules best explain the diversity observed in real food webs, such as that composed of plants, aphids, and their parasitoids. Using a suite of food-web models equipped with different dispersal rules, they show that preferential dispersal across trophic levels to sites where conspecifics are rare best fits the diversity observed in the empirical food web data in central Europe. Preferential dispersal from more centrally located sites to more remote sites does not provide a better fit to the empirical food web data than models assuming symmetric dispersal in the landscape. The authors argue this can be explained by individuals across trophic levels leaving sites with high conspecifics density and moving to sites with few individuals from their own species. They also provide empirical evidence that individuals dispersing preferentially to sites with few individuals from their own species predicts a critical distance between food webs at two sites beyond which their similarity sharply decreases. Their study provides simple dispersal rules that connect food-web dynamics at the local scale to the turnover rate of species and interactions across geographically distant food webs.

Melián, C.J., Křivan, V., Altermatt, F., Starý, P., Pellissier, L., De Laender, F. (2015). Dispersal dynamics in food webs. American Naturalist 185(2):157-168.

DOI: 10.1086/679505

http://www.jstor.org/stable/10.1086/679505