The two papers we picked this week related to food web structuring and the ways we explore complex communities. We delved into our discussions of food web dynamics starting with the classic paper on food webs in Rocky intertidal systems (Paine, 1966). This paper is often credited with demonstrating the ideas of keystone predators, based on the removal experiment of Pisaster sea stars which led to a decline in species diversity. Though this “classic” paper is often recommended reading for new ecologists, we found the concepts and ideas surprisingly underwhelming. Maybe it’s just knowledge we take for granted now that the field of ecology has progressed beyond describing who eats who.
We moved on to discuss a modern approach to mapping food web dynamics (Kéfi et al., 2015). This paper used an interaction network to assess trophic as well as non-trophic links in a food web. This type of network approach relies on a detailed understanding of all of the species interactions including competition and facilitation in addition to predation. Building this network requires in depth knowledge of the system but can highlight key areas of important interactions. For example, by including non-trophic interactions, Kefi et al demonstrated the importance of competition at basal trophic levels.
As a side note, while exploring some of the background on the Kefi et al. paper, we noticed that they went one step further by making an interactive online version of their network that can be found on the Chilean Ecological Network website (http://app.mappr.io/play/chile-marine-intertidal-network). This allows others to manipulate the web and visualize the different sets of interactions. I admit I probably spent 20 minutes just messing with the online app and getting a feel for the different species involved in different types of interactions. I found this online interactive web to be a great example of engaging and informative data visualization that supports their research.
While reading both of these papers, however, I was struck by the ways in which both were focused on direct species interactions through predation, competition, etc. and the distinct lack indirect interactions which may be just as important for structuring communities (Peacor & Werner, 2001).
Lastly, I’ve been reminded time and time again this semester that the major flaw with using food webs to understand a system is that they often exclude vital feedbacks with ecosystem processes. Food webs often ignore detrital pathways entirely and gloss over the vital role of decomposers in nutrient recycling. To that end, I would argue that the contributions of the Paine and Kefi papers are valuable for understanding the basic species interaction structure but a broader approach to food web ecology that expands on non-trophic and indirect interactions and incorporates an ecosystem perspective is vital to progress in this field.
- Kéfi, S., Berlow, E. L., Wieters, E. A., Joppa, L. N., Wood, S. A., Brose, U., & Navarrete, S. A. (2015). Network structure beyond food webs : mapping non-trophic and trophic interactions on Chilean rocky shores. Ecology, 96(1), 291–303.
- Paine, R. T. (1966). Food Web Complexity and Species Diversity. The American Naturalist, 100(910), 65–75. https://doi.org/10.1086/282400
- Peacor, S. D., & Werner, E. E. (2001). The contribution of trait-mediated indirect effects to the net effects of a predator. Proceedings of the National Academy of Sciences, 98(7), 3904–3908. https://doi.org/10.1073/pnas.071061998