The long-term and transient implications of multiple predators in biocontrol

Trophic flow of contamination: A nontrivial weapon for species coexistence

In the modern age of human-induced environmental changes, ecologists are increasingly alarmed about the potential disruption of ecosystems through toxicological processes. As humanity's footprint on the natural world expands, understanding these dynamics becomes crucial. While recent ecotoxicology research has mainly focused on entirely contaminated ecosystems, overlooking the effects of aquatic contamination on terrestrial predators with access to uncontaminated prey, our study addresses this gap. We present a prey-predator model for partially contaminated communities, where predators face a trade-off in prey preference between contaminated and uncontaminated sources. Through mathematical analysis and numerical simulations, we uncover some interpretable findings: (1) In uncontaminated environments, predation pressure may cause the extinction of one prey species. However, when even a small contamination level exists in alternative prey, endangered prey species can coexist with others. (2) Survival under high contamination depends on the predator's preference. A very low preference for contaminated prey trivially allows the predator to persist, while low or high preferences lead to the predator's exclusion. Surprisingly, intermediate preference leads to bi-stability between contaminated prey and predator extinction equilibrium, resulting in a trade-off between the presence of contaminated prey or the predator. (3) Our results confirm the abrupt extinction of predators due to contamination, driven by bistability between predator-free and coexisting states. However, our observation reveals that the likelihood of sudden predator extinction increases with a higher preference for contaminated prey. Additionally, we explore the robustness of these outcomes by considering flexible model assumptions and alternative parameter sets. In summary, our study offers valuable insights into the ecotoxicological processes within partially contaminated communities, shedding light on direct and indirect species interactions.

Anolis lizards as biocontrol agents in mainland and island agroecosystems

Our knowledge of ecological interactions that bolster ecosystem function and productivity has broad applications to the management of agricultural systems. Studies suggest that the presence of generalist predators in agricultural landscapes leads to a decrease in the abundance of herbivorous pests, but our understanding of how these interactions vary across taxa and along gradients of management intensity and eco‐geographic space remains incomplete. In this study, we assessed the functional response and biocontrol potential of a highly ubiquitous insectivore (lizards in the genus Anolis) on the world's most important coffee pest, the coffee berry borer (Hypothalemus hampei). We conducted field surveys and laboratory experiments to examine the impact of land‐use intensification on species richness and abundance of anoles and the capacity of anoles to reduce berry borer infestations in mainland and island coffee systems. Our results show that anoles significantly reduce coffee infestation rates in laboratory settings (Mexico, p = .03, F = 5.13 df = 1, 35; Puerto Rico, p = .014, F = 8.82, df = 1, 10) and are capable of consuming coffee berry borers in high abundance. Additionally, diversified agroecosystems bolster anole abundance, while high‐intensity practices, including the reduction of vegetation complexity and the application of agrochemicals were associated with reduced anole abundance. The results of this study provide supporting evidence of the positive impact of generalist predators on the control of crop pests in agricultural landscapes, and the role of diversified agroecosystems in sustaining both functionally diverse communities and crop production in tropical agroecosystems.

Nonrandom extinction patterns can modulate pest control service decline

Changes in biodiversity will mediate the consequences of agricultural intensification and expansion for ecosystem services. Regulating services, like pollination and pest control, generally decline with species loss. In nature, however, relationships between service provision and species richness are not always strong, partially because anthropogenic disturbances purge species from communities in nonrandom orders. The same traits that make for effective service providers may also confer resistance or sensitivity to anthropogenic disturbances, which may either temper or accelerate declines in service provision with species loss. We modeled a community of predators interacting with insect pest prey, and identified the contexts in which pest control provision was most sensitive to species loss. We found pest populations increased rapidly when functionally unique and dietary-generalist predators were lost first, with up to 20% lower pest control provision than random loss. In general, pest abundance increased most in the scenarios that freed more pest species from predation. Species loss also decreased the likelihood that the most effective service providers were present. In communities composed of species with identical traits, predators were equally effective service providers and, when competing predators went extinct, remaining community members assumed their functional roles. In more realistic trait-diverse communities, predators differed in pest control efficacy, and remaining predators could not fully compensate for the loss of their competitors, causing steeper declines in pest control provision with predator species loss. These results highlight diet breadth in particular as a key predictor of service provision, as it affects both the way species respond to and alter their environments. More generally, our model provides testable hypotheses for predicting how nonrandom species loss alters relationships between biodiversity and pest control provision.

The interplay between predator's prey preference and environmental heterogeneity in food web long-term stability

Prey preference of a predator is commonly used in models to analyze the timely issue of the relation among food web structure, diversity and stability. Given the variety of these terms in ecological literature, this work shows that domains of stability and species coexistence in food webs can be significantly altered by the chosen structure of predator's prey preference and environmental heterogeneity. Such results may bear upon issues in applied ecology, e.g., species conservation, biological control. More generally, they may serve as a caution with respect to the robustness of some results of food web theory.