Species' traits and food‐web complexity interactively affect a food web's response to press disturbance

Abstract

Citation: Wootton, K. L., and D. B. Stouffer. 2016. Species' traits and food-web complexity interactively affect a food web's response to press disturbance. Ecosphere 7(11):e01518. 10. 1002/ecs2.1518 Abstract. Given current levels of biodiversity loss and environmental change, studies of how food webs respond to disturbance should broaden their focus beyond short-term disturbances to explore the effects of long-term, "press" disturbances. Press disturbances often disproportionately impact one or a few species, but these impacts invariably propagate to the remaining species in the food web. Additionally, the way species interact with each other within the food web influences the impact they have on the rest of the food web if it is disturbed. Here, we investigate the effect of species-level press disturbances in a large set of model food webs. We simulated disturbances as a reduction in growth rate of a single species within the food web, which is analogous to a targeted disturbance such as selective fishing. In these simulations, we were particularly interested in the resistance of the food web-the magnitude of disturbance it could tolerate before any species went extinct. We found that more highly connected and biodiverse food webs had lower resistance and were more likely to lose species at a low level of disturbance than sparsely connected food webs with few species. Food-web complexity also influenced which species were likely to go extinct due to the disturbance. At low species richness and/or low connectance, food webs could tolerate a large disturbance, and it was usually the focal species which went extinct. In contrast, webs were less stable at higher levels of complexity and a small disturbance rapidly propagated and caused the extinction of a non-focal species. Lastly, the disturbed species' traits were also important: Disturbance of a species with few interactions usually resulted in its own extinction, while disturbance of a species with many interactions more often caused the extinction of the disturbed species' predator(s). Likewise, the trophic level of the disturbed species influenced which species went extinct, although this was modulated by the complexity of the food web. Overall, our study indicates that both the traits of disturbed species and the complexity of the food web need to be considered in attempts to predict or manage the ecological impact of press disturbances.

Unveiling dimensions of stability in complex ecological networks

“…Structural stability (43,44) to these 2 types of press perturbations is assessed with the tolerance metrics (Table 1). Tolerance to mortality is measured as in previous studies (45,46), and tolerance to extinctions is measured with robustness (47). We also include metrics of community resistance to random extinctions (48) as cascading extinctions.…”

Stable motifs delay species loss in simulated food webs

“…This complements other work identifying sets of species which are more vulnerable to extinction due to their traits (Curtsdotter et al, 2011;Ryser et al, 2019). Since the trophic level and degree of the species being removed can also affect which species, if any, go secondarily extinct (Wootton & Stouffer, 2016b;Dunne et al, 2002), the properties of both disturbed and non-disturbed species affect the ways in which extinctions can cascade through a food web. The stronger correlation of extinction orders in larger, more-connected networks, as well as the somewhat shorter mean times to extinction in these webs (Fig.…”

River food chains lead to riparian bats and birds in two mid‐order rivers

“…Food chain length is a measure of food web architecture and is related to the complexity of trophic interactions leading to a top consumer (Sabo et al 2009). Longer food chains tend to have more biodiversity and resilience to environmental changes (Pimm andLawton 1977, Pimm 1984), though this depends on degree of omnivory, species richness, and individual lifehistory traits (Downing andLeibold 2010, Wootton andStouffer 2016). Environmental controls on food chain length include ecosystem size, disturbance, and resource availability (Post 2002).…”