Food-web flexibility effects on network stability and ecosystem processes
Zusammenfassung der Projektergebnisse
This project addressed the interplay between the body-size structures of natural food webs, adaptive foraging strategies of consumers and the size structure of populations (separation of discrete size classes for juveniles and adults) in determining food-web stability. In the first sub-project, we analyzed the body-size structure of natural food web describing the patterns (1) how body sizes are distributed across species and (2) how network parameters of the food webs are correlated with these patterns. We found a systematic structure across ecosystem types that is characterized by five patterns: (1) predator and prey body sizes are positively correlated; (2) predator body size increases with the trophic level (i.e., the size of the species increases along to food chains from small basal to large top species); (3) the predator-prey body-size ratio (i.e., ratio of predator to prey size) decreases with trophic level indicating that along food chains predator and prey become more similar in size; (4) the generality of predators (i.e., the number of prey species they consume) increases with their size; (5) the vulnerability of species (i.e., the number of predator species that they have) decreases with their size. In two empirical meta-analyses, it was documented that these patterns generally hold with few exceptions across ecosystems. In the first modeling project, we addressed one aspect of stability: the risk of secondary extinctions. We found a strong correlation between the community size structure and the risk of secondary extinctions. In particular, the distribution of abundances across body-size classes may become a useful tool for characterizing communities that are most sensitive to secondary extinctions. In the second modeling study, we addressed how adaptive flexibility of consumer foraging interacts with the community size structure in determining foodweb stability. We found that both processes can stabilize complex food webs substantially. Interestingly, adaptive foraging in food webs that initially have a random structure generates final linkage structures that are similar to those that start with a body-size structure that is consistent with natural ecosystems. This suggests that adaptive consumer behavior might be a process that leads to the emergence of the natural size structures that were documented in the empirical studies of this project. In the final modeling study, we combined natural body size structures across the populations of complex food webs with adaptive foraging and size structured populations (including small juvenile and large adult subpopulations). We documented that both levels of flexibility have a combined effect on food-web stability. Together, the studies of this project have thus provided a general understanding how population processes and the distribution of body sizes across species have a synergistic effect on community-level patterns such as food-web stability.
Projektbezogene Publikationen (Auswahl)
- (2011): Size-based food web characteristics govern the response to species extinctions. Basic and Applied Ecology 12(7): 581-589
Riede, J.O,, Binzer, A., Brose, U., de Castro, F., Curtsdotter, A., Rall, B.C. & Eklöf, A.
- (2011): Stepping in Elton's footprints: a general scaling model for body masses and trophic levels across ecosystems. Ecology Letters 14: 169- 178
Riede, J., Brose, U., Ebenman, B., Jacob, U., Thompson, R., Townsend, C.R., & Jonsson, T.
- Body sizes, cumulative and allometric degree distributions across natural food webs. Oikos 120: 503-509
Digel, C., Riede, J.O. & Brose, U.
- (2012): Interactive effects of bodysize structure and adaptive foraging on food-web stability. Ecology Letters 15(3): 243-250
Heckmann, L., Drossel, B., Brose, U. & Guill, C.
(Siehe online unter https://doi.org/10.1111/j.1461-0248.2011.01733.x)
