Dynamic population stage structure due to juvenile–adult asymmetry stabilizes complex ecological communities

Abstract

Natural ecological communities are diverse, complex, and often surprisingly stable, but the mechanisms underlying their stability remain a theoretical enigma. Interactions such as competition and predation presumably structure communities, yet theory predicts that complex communities are stable only when species growth rates are mostly limited by intraspecific self-regulation rather than by interactions with resources, competitors, and predators. Current theory, however, considers only the network topology of population-level interactions between species and ignores within-population differences, such as between juvenile and adult individuals. Here, using model simulations and analysis, I show that including commonly observed differences in vulnerability to predation and foraging efficiency between juvenile and adult individuals results in up to 10 times larger, more complex communities than observed in simulations without population stage structure. These diverse communities are stable or fluctuate with limited amplitude, although in the model only a single basal species is self-regulated, and the population-level interaction network is highly connected. Analysis of the species interaction matrix predicts the simulated communities to be unstable but for the interaction with the population-structure subsystem, which completely cancels out these instabilities through dynamic changes in population stage structure. Common differences between juveniles and adults and fluctuations in their relative abundance may hence have a decisive influence on the stability of complex natural communities and their vulnerability when environmental conditions change. To explain community persistence, it may not be sufficient to consider only the network of interactions between the constituting species.

Interaction between hunting strategy, habitat type and stratum drive intraguild predation and cannibalism

“…Cannibalism in predator populations inherently creates ontogenetic asymmetries in vulnerability to predation and food‐limitation due to a non‐consumptive effect when individuals reduce foraging activity to avoid predation (Schmidt and Rypstra 2001). These ontogenetic asymmetries are predicted to allow the coexistence of species in highly diverse communities (de Roos 2021). Overall, our results match with the theoretical predictions that cannibalism with a self‐limiting effect and the existence of intraspecific ontogenetic asymmetries may reinforce coexistence in communities with IGP among functionally similar predators (Rudolf 2001, Amarasekare 2008, Toscano et al 2001, de Roos 2021).…”

“…These ontogenetic asymmetries are predicted to allow the coexistence of species in highly diverse communities (de Roos 2021). Overall, our results match with the theoretical predictions that cannibalism with a self‐limiting effect and the existence of intraspecific ontogenetic asymmetries may reinforce coexistence in communities with IGP among functionally similar predators (Rudolf 2001, Amarasekare 2008, Toscano et al 2001, de Roos 2021). Therefore, the relative separation of exploitation and predation as well as the reinforcement of intraspecific clustering through cannibalism represent a potential explanation for the coexistence of the hyper‐diverse spider communities despite theoretical predictions.…”

“…The self‐limiting cannibalism may then enable coexistence in diverse predator communities despite high killing frequencies among functionally redundant predators. Cannibalism may also produce intraspecific asymmetries between juveniles and adults as juveniles become more vulnerable and food‐limited than adults (Rypstra and Samu 2001, Schmidt and Rypstra 2001) which is also important for species coexistence in diverse predator communities (de Roos 2021).…”

A bioenergetic framework for aboveground terrestrial food webs

“…Species can either consume or be consumed by different species as they grow and mature [66]. Integrating ontogenetic structure into aquatic food web models has had varied effects on food web dynamics, with some showing increased stability [67] due to tradeoffs or emergent facilitation [68], and others showing decreased stability through ontogenetic niche shifts [66]. Terrestrial food web models integrating plant ontogeny remain scarce, though preliminary work indicates the potential for emergent facilitation in certain food web motifs at the autotroph level [69].…”

Effect of delay on the emergent stability patterns in generalized Lotka–Volterra ecological dynamics

“…P(t-τ), Z(t-τ) and F(t-τ). In addition, there have been developed a lot of mechanisms that may induce delay interactions in the ecosystems such as: maturation period [35] (see also fig. 3 of [36]), a gestation period [37], feeding times and hunger coefficients in predator-prey interactions [38], replenishment or regeneration time for resources (e.g.…”