Interactions between predation and disturbances shape prey communities

Abstract

Ecological disturbances are important drivers of biodiversity patterns. Many biodiversity studies rely on endpoint measurements instead of following the dynamics that lead to those outcomes and testing ecological drivers individually, often considering only a single trophic level. Manipulating multiple factors (biotic and abiotic) in controlled settings and measuring multiple descriptors of multi-trophic communities could enlighten our understanding of the context dependency of ecological disturbances. Using model microbial communities, we experimentally tested the effects of imposed disturbances (i.e. increased dilution simulating density-independent mortality as press or pulse disturbances coupled with resource deprivation) on bacterial abundance, diversity and community structure in the absence or presence of a protist predator. We monitored the communities immediately before and after imposing the disturbance and four days after resuming the pre-disturbance dilution regime to infer resistance and recovery properties. The results highlight that bacterial abundance, diversity and community composition were more affected by predation than by disturbance type, resource loss or the interaction of these factors. Predator abundance was strongly affected by the type of disturbance imposed, causing temporary relief of predation pressure. Importantly, prey community composition differed significantly at different phases, emphasizing that endpoint measurements are insufficient for understanding the recovery of communities.

Diversity and coexistence are influenced by time‐dependent species interactions in a predator–prey system

“…These prey species are common free‐living micro‐organisms in aquatic and soil ecosystems. They follow a strict competitive hierarchy, with A>K>S>W (see Karakoç et al 2018), and their different colony colours allow clear distinction and quantification on agar plates (Saleem et al 2012, 2013). Prior to experiments, they were grown in pure cultures in Brunner‐CR2 medium (Saleem et al 2012) overnight at 25 °C in a shaking incubator.…”

“…Microcosms were incubated for 34 days, corresponding to c . 60–120 generations for all species (Karakoç et al 2018). The remaining culture after each daily transfer was used to estimate species abundances during the experimental period from 3 to 34 days after the start of the experiment.…”

The dimensionality of stability depends on disturbance type

“…Importantly, understanding the mechanisms underpinning the responses of DS requires that future experiments on real and in-silico systems manipulate potential mechanisms, generally the strength and sign of species interactions, and the stochasticity of the system's dynamics (which may be achieved by manipulating levels of demographic and environmental stochasticity, response diversity, dispersal abilities and environmental sensitivities of the species in the community). For such experiments the use of modelling studies, as done here, seems a useful way forward, because collection of such data empirically is feasible only in micro-and mesocosm settings (Baert et al 2016b;Garnier et al 2017;Karakoc ß et al 2018;Pennekamp et al 2018). Importantly, although measuring DS was rather easy in our modelling study, empirical studies may be limited because of the difficulty to measure multiple stability properties in natural systems.…”

A theory of pulse dynamics and disturbance in ecology

“…This structure consists of a set of four fundamental postulates and the relationships among them that together circumscribe the common denominators and rules for all pulse events. Although disturbances can initiate successional change, we do not review theories of successional mechanisms and pathways here (see Glenn-Lewin et al 1992, Meiners et al 2015, Peet 1992, Walker and del Moral 2003, Walker and Wardle 2014, Pulsford et al 2016; nor do we treat the dynamics among species that occur after pulse initiation, such as trophic interactions (see Holt 2008, Nowlin et al 2008, Karakoc ß et al 2018).…”