Functional Response and Control Potential of Orius sauteri (Hemiptera: Anthocoridae) on Tea Thrips (Dendrothrips minowai Priesner)

This study aimed to clarify the functional response and control potential of O. sauteri in relation to tea thrips. The functional response, interference response, and control potential of O. sauteri on adult tea thrips, in different insect stages and environment temperatures, were studied. The results showed that the predation of O. sauteri against tea thrips was positively correlated with prey density, while the effects of searching for O. sauteri on the adult tea thrips were negatively correlated with prey density. The predation effects of O. sauteri on tea thrips were also influenced by prey density, which indicated that there was an intra-specific interference response from predators to tea thrips. The population density of tea thrips was significantly decreased, and O. sauteri showed a remarkable ability to control them when the benefit-to-harm ratio was 3:100.

Effects of Macrobiota on the Transfer Efficiency of Essential Elements and Fatty Acids From Phytoplankton to Zooplankton Under Eutrophic Conditions

The transfer pathways of organic matter and elements from phytoplankton to zooplankton in freshwater ecosystems are important for understanding how aquatic ecosystems function. We conducted a mesocosm experiment to determine how fish and zebra mussels altered the transfer efficiencies of essential substances including carbon (C), polyunsaturated fatty acids (PUFAs), total fatty acids (FAs), phosphorus (P), and nitrogen (N) from phytoplankton to zooplankton. We assessed the transfer efficiencies of the essential substances from phytoplankton to zooplankton as the ratio of their zooplankton production (P) per unit of biomass (B) to that of phytoplankton to exclude grazing or predation effects. We hypothesized that zebra mussels and fish would affect the transfer of materials from phytoplankton to zooplankton by altering the contents of essential elements and FAs in phytoplankton and zooplankton communities and/or due to shifts in the planktonic community structure mediated by grazing and/or predation. Fish increased the transfer efficiencies of eicosapentaenoic acid 20:5 ω-3 (EPA), docosahexaenoic acid 22:6 ω-3 (DHA), and P relative to the control. We speculated that fish weakened the control of zooplankton over algal assemblage by selectively feeding on larger cladocerans such as Daphnia. Therefore, fish can increase the relative proportion of high-quality food for zooplankton, improving food conditions for the available zooplankton. In contrast, zebra mussels reduced the transfer efficiencies of EPA and DHA relative to the control treatment likely due to competition with zooplankton for PUFA-rich food particles. However, zebra mussels did not have any impact on the transfer efficiencies of C, total FAs, N, and P. EPA, DHA, and P were transferred more efficiently than C from phytoplankton to zooplankton, while total FAs, which are commonly used as an energetic source, were transferred as efficiently as C. The enrichment of consumers with the most important substances relative to their basal food sources creates the potential for the successful transport of these substances across aquatic trophic webs.

Top-down effects of foraging decisions on local, landscape and regional biodiversity of resources (DivGUD)

Foraging by consumers acts as a biotic filtering mechanism for biodiversity at the trophic level of resources. Variation in foraging behaviour have cascading effects on abundance, diversity, and functional trait composition of the community of resource species. Here we propose diversity at giving-up density (DivGUD), when foragers quit exploring a patch, as a novel concept and simple measure to quantify these effects at multiple spatial scales. In experimental landscapes, patch residency of wild rodents decreased local α-DivGUD (via elevated mortality of species with large seeds) and regional γ-DivGUD, while dissimilarity among patches in a landscape (ß-DivGUD) increased. Thus, DivGUD provides a framework linking theories of adaptive foraging behaviour with community ecology allowing to investigate cascading indirect predation effects across multiple trophic levels e.g. the ecology-of-fear framework; feedbacks between functional trait composition of resource species and consumer communities; and effects of inter-individual differences among foragers on the biodiversity of resource communities.

Dynamics of a stochastic population model with predation effects in polluted environments

The present paper puts forward and probes a stochastic single-species model with predation effect in a polluted environment. We propose a threshold between extermination and weak persistence of the species and provide sufficient conditions for the stochastic persistence of the species. In addition, we evaluate the growth rates of the solution. Theoretical findings are expounded by some numerical simulations.

Scavenging Effects of Large CanidsBoth authors contributed equally to this work

SynopsisMany large predators are also facultative scavengers that may compete with and depredate other species at carcasses. Yet, the ecological impacts of facultative scavenging by large predators, or their “scavenging effects”, still receive relatively little attention in comparison to their predation effects. To address this knowledge gap, we comprehensively examine the roles played by, and impacts of, facultative scavengers, with a focus on large canids: the African wild dog (Lycaon pictus), dhole (Cuon alpinus), dingo (Canis dingo), Ethiopian wolf (C. simensis), gray wolf (C. lupus), maned wolf (Chrysocyon brachyurus), and red wolf (C. rufus). Specifically, after defining facultative scavenging as use or usurpation of a carcass that a consumer has not killed, we (i) provide a conceptual overview of the community interactions around carcasses that can be initiated by facultative scavengers, (ii) review the extent of scavenging by and the evidence for scavenging effects of large canids, (iii) discuss external factors that may diminish or enhance the effects of large canids as scavengers, and (iv) identify aspects of this phenomenon that require additional research attention as a guide for future work.

Predators affect a plant virus through direct and trait-mediated indirect effects on vectors

Arthropods that vector plant pathogens often interact with predators within food webs. Predators affect vectors by eating them (consumptive effects) and by inducing antipredator behaviors (non-consumptive effects), and these interactions may affect transmission of vector-borne pathogens. However, it has proven difficult to experimentally tease apart the effects of predators on vector fitness and behavior as they are often correlated. We addressed this problem by assessing how both aphids and an aphid-borne pathogen were affected by variable predation risk. Specifically, we experimentally manipulated ladybeetle predators’ mouthparts to isolate consumptive, and non-consumptive, effects of predators on aphid fitness, movement, and virus transmission. We show that although lethal predators decreased aphid vector abundance, they increased pathogen transmission by increasing aphid movement among hosts. Moreover, aphids responded to risk of predation by moving to younger plant tissue that was more susceptible to the pathogen. Aphids also responded to predator risk through compensatory reproduction, which offset direct consumptive effects. Our results support predictions of disease models showing alterations of vector movement due to predators can have greater effects on transmission of pathogens than vector consumption. Broadly, our study shows isolating direct and indirect predation effects can reveal novel pathways by which predators affect vector-borne pathogens.

Giving-up diversity (GUDiv): top-down effects of foraging decisions on local, landscape and regional biodiversity of resources

Foraging by consumers has direct effects on the community of their resource species, and may serve as a biotic filtering mechanism of diversity. Determinants of foraging behaviour may thus have cascading effects on abundance, diversity, and functional trait composition of the resource community. Here we propose giving-up diversity (GUDiv) as a novel concept and simple measure to quantify community effects of foraging at multiple spatial diversity scales. GUDiv provides a framework linking theories of adaptive foraging behaviour with community ecology. In experimental resource landscapes we showcase effects of patch residency of foraging wild rodents on α-GUDiv, ß-GUDiv and γ- GUDiv, and on functional trait composition of resources. Using GUDiv allows for prediction-based investigation of cascading indirect predation effects (ecology of fear) across multiple trophic levels, of feedbacks between functional trait composition of resource and consumer communities, and of effects of inter-individual differences among foragers on the diversity of resource communities.

Sensory-based quantification of male colour patterns in Trinidadian guppies reveals nonparallel phenotypic evolution across an ecological transition in multivariate trait space

ABSTRACTParallel evolution, in which independent populations evolve along similar phenotypic trajectories, offers insights into the repeatability of adaptive evolution. Here, we revisit a classic example of parallelism, that of repeated evolution of brighter males in the Trinidadian guppy. In guppies, colonisation of low predation habitats is associated with emergence of ‘more colourful’ phenotypes since predator-induced viability selection for crypsis weakens while sexual selection by female preference for conspicuity remains strong. Our study differs from previous investigations in three respects. First, we adopt a multivariate phenotyping approach to characterise parallelism in multi-trait space. Second, we use ecologically-relevant colour traits defined by the visual systems of the two selective agents (i.e. guppy, predatory cichlid). Third, we estimate population genetic structure to test for adaptive (parallel) evolution against a model of neutral phenotypyc divergence. We find strong phenotypic differentiation that is inconsistent with a neutral model, but only limited support for the predicted pattern of greater conspicuity at low predation. Effects of predation regime on each trait were in the expected direction, but weak, largely non-significant, and explained little among-population variation. In multi-trait space, phenotypic trajectories of lineages colonising low from high predation regimes were not parallel. Our results are consistent with reduced predation risk facilitating adaptive differentiation by female choice, but suggest that this proceeds in (effectively) independent directions of multi-trait space across lineages. Pool-sequencing data also revealed SNPs showing greater differentiation than expected under neutrality and/or associations with known colour genes in other species, presenting opportunities for future genetic study.