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BACKGROUND: Predation plays a pivotal role in the composition and functioning of ecosystems. Both habitat complexity and predator density are important contexts which may determine the strength of trophic and non-trophic interactions. In aquatic systems, the efficacy of natural enemies in regulating vector pest species could be modified by such context dependencies. Here, we use a functional response (FR) approach to experimentally quantify conspecific multiple predator effects across a habitat complexity gradient of two notonectids, Anisops sardea and Enithares chinai, towards larvae of the vector mosquito Culex pipiens pipiens.RESULTS: E. chinai exhibited significantly greater consumption rates than A. sardea across habitat complexities, both as individuals and conspecific pairs. Each predator type displayed Type II FRs across experimental treatments, with synergistic multiple predator effects (i.e. prey risk enhancement) displayed in the absence of habitat complexity. Effects of increasing habitat complexity modified multiple predator effects differentially between species given behavioral differences, with habitat complexity causing significant antagonism (i.e. prey risk reduction) with multiple A. sardea compared to E. chinai.CONCLUSION: Habitat complexity effects on multiple predator interactions can manifest differently at the species level, suggesting emergent effects which complicate predictions of natural enemy impact in heterogenous environments. Considerations of density, diversity and habitat effects on efficacies of natural enemies should thus be considered by pest management practitioners to better explain biocontrol efficacies in increasingly diverse environments.

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Background Predators play a critical role in regulating larval mosquito prey populations in aquatic habitats. Understanding predator-prey responses to climate change-induced environmental perturbations may foster optimal efficacy in vector reduction. However, organisms may differentially respond to heterogeneous thermal environments, potentially destabilizing predator-prey trophic systems. Methods Here, we explored the critical thermal limits of activity (CTLs; critical thermal-maxima [CTmax] and minima [CTmin]) of key predator-prey species. We concurrently examined CTL asynchrony of two notonectid predators (Anisops sardea and Enithares chinai) and one copepod predator (Lovenula falcifera) as well as larvae of three vector mosquito species, Aedes aegypti, Anopheles quadriannulatus and Culex pipiens, across instar stages (early, 1st; intermediate, 2nd/3rd; late, 4th). Results Overall, predators and prey differed significantly in CTmax and CTmin. Predators generally had lower CTLs than mosquito prey, dependent on prey instar stage and species, with first instars having the lowest CTmax (lowest warm tolerance), but also the lowest CTmin (highest cold tolerance). For predators, L. falcifera exhibited the narrowest CTLs overall, with E. chinai having the widest and A. sardea intermediate CTLs, respectively. Among prey species, the global invader Ae. aegypti consistently exhibited the highest CTmax, whilst differences among CTmin were inconsistent among prey species according to instar stage. Conclusion These results point to significant predator-prey mismatches under environmental change, potentially adversely affecting natural mosquito biocontrol given projected shifts in temperature fluctuations in the study region. The overall narrower thermal breadth of native predators relative to larval mosquito prey may reduce natural biotic resistance to pests and harmful mosquito species, with implications for population success and potentially vector capacity under global change.

Biodiversity assessments are indispensable tools for planning and monitoring conservation strategies. Camera traps (CT) are widely used to monitor wildlife and have proven their usefulness. Environmental DNA (eDNA)‐based approaches are increasingly implemented for biomonitoring, combining sensitivity, high taxonomic coverage and resolution, non‐invasiveness and easiness of sampling, but remain challenging for terrestrial fauna. However, in remote desert areas where scattered water bodies attract terrestrial species, which release their DNA into the water, this method presents a unique opportunity for their detection. In order to identify the most efficient method for a given study system, comparative studies are needed. Here, we compare CT and DNA metabarcoding of water samples collected from two desert ecosystems, the Trans‐Altai Gobi in Mongolia and the Kalahari in Botswana. We recorded with CT the visiting patterns of wildlife and studied the correlation with the biodiversity captured with the eDNA approach. The aim of the present study was threefold: (a) to investigate how well waterborne eDNA captures signals of terrestrial fauna in remote desert environments, which have been so far neglected in terms of biomonitoring efforts; (b) to compare two distinct approaches for biomonitoring in such environments; and (c) to draw recommendations for future eDNA‐based biomonitoring. We found significant correlations between the two methodologies and describe a detectability score based on variables extracted from CT data and the visiting patterns of wildlife. This supports the use of eDNA‐based biomonitoring in these ecosystems and encourages further research to integrate the methodology in the planning and monitoring of conservation strategies.