Trait-mediated Indirect Interactions Research Articles

The role of manipulative trophically transmitted parasites in the stability of a predator–prey community

In this paper, we are interested in the effect of a trophically transmitted parasite on the structure and dynamics of a resident predator–prey community. The parasite, apart from increasing the mortality rates of its hosts, can also change their physiology or their behaviour, which is known as trait-mediated indirect interaction. We assume that parasite transmission, which entails rapid physiological or behavioural change, is a fast process with respect to the community dynamics, including prey and predator growths and predation. This existence of different time scales allows us to provide analytical results to understand some conditions under which the parasite change the dynamics of the predator–prey community. Thus, we are able to find conditions under which indirect trait-mediated interactions induced by the parasite lead to a coexistence between predators and prey that would not occur in its absence. We also provide conditions, evolutionary deleterious, that ensure the extinction of a predator–prey community that would be viable without parasite intervention. Finally, we show situations in which the action of the parasite destabilizes the predator–prey system without eliminating it, producing oscillations, the mechanism of which is analysed.

Keep Your Eggs Away: Ant Presence Reduces Ceratitis capitata Oviposition Behaviour through Trait-Mediated Indirect Interactions.

Alternative methods to achieve sustainable agricultural production while reducing the use of chemical pesticides, such as biological control, are increasingly needed. The exploitation of trait-mediated indirect interactions (TMIIs), in which pests modify their behavior in response to some cues (e.g., pheromones and other semiochemicals) to avoid predation risk, may be a possible strategy. In this study, we tested the effect of TMIIs of two Mediterranean ant species, Crematogaster scutellaris and Tapinoma nigerrimum, on the oviposition behaviour of Ceratitis capitata (Diptera: Tephritidae), one of the world's most economically damaging pests, which attacks fruits. For each ant species, we performed choice experiments using ant-scented and control plums, counting the time spent by medflies on fruits and the number of pupae emerging from them. Results of both ant species tests showed a significantly shorter time spent by ovipositing medflies on ant-exposed plums and a lower number of pupae, when compared to the control group. Our findings highlighted that the semiochemicals released by ants on plums triggered an avoidance behaviour by medfly females, leading to lower oviposition rates. This study contributes to the understanding of indirect ant-pest interactions in Mediterranean agricultural settings and points out the potential of utilising ant-borne semiochemicals in sustainable IPM strategies.

Prey–predator dynamics with adaptive protection mutualism

Prey can ease the burden of exploitation by attracting a third party that interferes with their predators. Such is the case for plant-ant or aphid-ant mutualisms, where the victim supplies food to the ants, while the ants attack or drive away the offenders. Since ants are adaptive foragers, defense services can be altered by alternative food sources (e.g., other plants, or human-supplied resource). This article explores the prey-predator-ant system, using a model that combines predator-prey population dynamics with ant optimal foraging, where ants consume prey-supplied resources or alternative resources. Feedbacks between prey-predator dynamics and adaptive ant foraging leads to complex dynamics. For a given ant colony size and supply rate of alternative resources, prey can coexist with predators at alternative stable states, or along alternative limit cycles. Limit cycles extend the scope of defensive mutualism beyond the point where ants would abandon prey in favor of alternative resources under equilibrium conditions. These results highlight the importance of trait-mediated indirect interactions for natural mutualistic–antagonistic systems, and potential outcomes of manipulating ant defense services using baits in the case of agriculture.

Emergent effects of two rocky intertidal predators on prey: Interaction of crabs and sea-stars may reduce mussel mortality

Two predator – one prey systems are widespread in nature, and have been important to both ecological theory and practice. A primary question for these systems is whether the two predators produce “emergent effects”: greater or less prey mortality than expected based on the two predators acting alone. We conducted an in-lab experiment on a two predator (the crab Cancer productus and the sea-star Evasterias troschelii), one prey (the bivalve Mytilus trossulus) system common to the marine rocky intertidal of the northeastern Pacific. In 156 mesocosm experimental trials, mortality rates of M. trossulus were compared between Crabs only, Sea-stars only, and a Mixed treatment with both predators present. The experiment used a substitutive design, i.e., predator density was held constant. Based on a Linear Mixed Effects Model, the interactive effects of the number of predator species and water temperature had the greatest effect on mussel mortality. For the observed temperature range, the two predators in the Mixed treatment killed fewer mussels than expected based on the average mussel mortality of the one-predator treatments. As the two predators were never observed to interfere with each other directly, the reduced prey mortality is possibly a trait-mediated indirect interaction, involving behavioral modification (mutual avoidance) on the part of the predators. Temperature may mediate these results; crabs consumed more mussels at higher temperatures while sea-stars did so at lower temperatures. As these experiments were conducted over a large part of the known temperature range for this region, these results suggest that mussels may experience seasonal shifts in both predation rates and the identity of the predator, which should be investigated in future field studies. Increasingly warmer temperatures anticipated in the coming century could increase mussel mortality due to predation by cancrid crabs, which appear to have temperature responsive feeding rates. Understanding this two-predator one-prey system better is particularly important given that mussels are important foundational species, and recent climate change has affected abundances of the taxa involved.

Destabilizing effects on a classic tri-trophic oyster-reef cascade.

How interactions among multiple predators affect the stability of trophic cascades is a topic of special ecological interest. To examine factors affecting the stability of the classic tri-trophic oyster reef cascade within a different context, configurations of three predators, including the Gulf toadfish, Gulf stone crab, and oystershell mud crab, were manipulated together with either oyster shell or limestone gravel substrate within a multiple predator effects (MPE) experiment. Additionally, a complimentary set of trait-mediated-indirect interaction (TMII) experiments examined the inhibition of oyster consumption relative to mud-crab size and top predator identity in the absence of other cues and factors. The classic tri-trophic cascade formed by the toadfish-mud crab-oyster configuration was potentially weakened by several interactions within the MPE experiment. Consumption of oysters and mud crabs by the intraguild stone crab was undeterred by the presence of toadfish. Although mud crab feeding was inhibited in the presence of both toadfish and stone crabs, estimated non-consumptive effects (NCEs) were weaker for stone crabs in the MPE experiment. Consequently, the total effect was destabilizing when all three predator species were together. Inhibition of mud crab feeding was inversely related to direct predation on mud crabs within the MPE experiment. Complimentary TMII experiments revealed greater inhibition of mud crab feeding in response to stone crabs under sparse conditions. TMII experiments also implied that inhibition of mud crab feeding could have largely accounted for NCEs relative to oysters within the MPE experiment, as opposed to interference by other mud crabs or top predators. An inverse relationship between mud crab size and NCE strength in the TMII experiment disclosed another potentially destabilizing influence on the tri-trophic-cascade. Finally, although habitat complexity generally dampened the consumption of oysters across MPE treatments, complex habitat promoted mud crab feeding in the presence of toadfish alone. This study underscores how ecological interactions can mediate trophic cascades and provides some additional insights into the trophic dynamics of oyster reefs for further testing under natural conditions.

Coexistence and extinction in a data-based ratio-dependent model of an insect community.

In theory, pure competition often leads to competitive exclusion of species. However, what we often see in nature is a large number of distinct predator or consumer species coexist in a community consisting a smaller number of prey or plant species. In an effort of dissecting how indirect competition and selective predation may have contributed to the coexistence of species in an insect community, according to the replicated cage experiments (two aphid species and a specialist parasitoid that attacks only one of the aphids) and proposed mathematical models, van Veen et. al. [5] conclude that the coexistence of the three species is due to a combination of density-mediated and trait-mediated indirect interactions. In this paper, we formulate an alternative model that observes the conventional law of mass conservation and provides a better fitting to their experimental data sets. Moreover, we present an initial attempt in studying the stabilities of the nonnegative steady states of this model.

Behavioural mechanisms underlying parasite-mediated competition for refuges in a coral reef fish

Parasites have been increasingly recognized as participants in indirect ecological interactions, including those mediated by parasite-induced changes to host behaviour (trait-mediated indirect interactions or TMIIs). In most documented examples, host behaviours altered by parasites increase susceptibility to predation because the predator is also a host (host-manipulation). Here, we test for a TMII in which a parasitic copepod modifies the predator-prey interaction between a small goby host and several larger predatory fish. Gobies compete for crevices in the reef to avoid predation and goby mortality increases more rapidly with increasing refuge shortage for parasitized gobies than for those free of parasites. We found interactive effects of refuge shortage and parasitism on two behaviours we predicted might be associated with parasite-mediated competition for refuges. First, as refuge-shortage increases, the rate of aggression among gobies increases and parasitism intensifies this interaction. Second, goby proximity to refuges increases as refuges become scarce, but parasitism nullifies this increase. In combination, these parasite-induced changes in behaviour may explain why parasitized gobies are poor competitors for refuges. Because the parasite is not trophically transmitted via host manipulation, these altered behaviours in parasitized gobies are likely coincidental to infection.

Trait-mediated indirect interactions: Moose browsing increases sawfly fecundity through plant-induced responses.

Induced responses in plants, initiated by herbivory, create potential for trait‐mediated indirect interactions among herbivores. Responses to an initial herbivore may change a number of plant traits that subsequently alter ecological processes with additional herbivores. Although common, indirect interactions between taxonomically distant herbivores, such as mammals and insects, are less studied than between taxonomically related species (i.e., insect–insect). In terms of mammal–insect interactions, effects on insect numbers (e.g., density) are relatively well studied, whereas effects on performance (e.g., fecundity) are rarely explored. Moreover, few studies have explored mammal–insect interactions on coniferous plants.The aim of this study was to investigate the effect of mammalian induced responses on insect performance. We specifically investigated the effect of moose (Alces alces) browsing on Scots pine (Pinus sylvestris) and subsequent effects on sawfly (Neodiprion sertifer) performance.Sawfly larvae were reared on browsed, clipped, and unbrowsed control pine trees in a controlled field experiment. Afterward, cocoon weight was measured. Needle C:N ratio and di‐terpene content were measured in response to browsing.Sawfly performance was enhanced on trees browsed by moose. Cocoon weight (proxy for fecundity) was 9 and 13% higher on browsed and clipped trees compared to unbrowsed trees. Cocoon weight was weakly related to needle C:N ratio, and browsed trees had lower a C:N ratio compared to unbrowsed trees. Needle di‐terpene content, known to affect sawfly performance, was neither affected by the browsing treatments nor did it correlate with sawfly weight.We conclude that mammalian herbivory can affect insect herbivore performance, with potential consequences for ecological communities and with particular importance for insect population dynamics. The measured plant variables could not fully explain the effect on sawfly performance providing a starting point for the consideration of additional plant responses induced by mammalian browsing affecting insect performance.

Mistletoe generates non‐trophic and trait‐mediated indirect interactions through a shared host of herbivore consumers

AbstractIndirect interactions emerge among a wide range of herbivores sharing the same plant resource. Consumers usually belong to different trophic guilds, from folivores and sapsuckers to parasitic plants. We propose that mistletoes parasitizing pines could play a key role acting as herbivores on host pines and coming indirectly into competition with other herbivores feeding on the same host. Changes caused by mistletoes on its host have been well studied, but its effects running across trophic webs remain unrevealed. In this study, we investigate the effect of European mistletoe (Viscum album subsp. austriacum) on the host‐feeding herbivores via trait‐mediated indirect interactions (TMIIs) across their shared pine host (Pinus nigra subsp. salzmannii). We performed field and laboratory experiments, and analyzed the net effect of different mistletoe parasite loads on three host‐phytophagous species: the sapsucker Cinara pini (Aphididae), the winter folivore Thaumetopoea pityocampa (Thaumetopoeidae), and the summer folivore Brachyderes sp. (Curculionidae), all being members of different functional feeding groups (FFGs). We summarize the mistletoe–host–herbivore interactions by means of a TMII, where mistletoe parasitism causes non‐trophic links and detrimental indirect interactions on pine‐feeding herbivores across its shared host, suggesting a worsening of host quality as food. These indirect interactions vary according to three parameters. First, the intensity has a non‐proportional relation with parasite load, showing an impact threshold on highly parasitized pines. Second, the movement capacity of insect herbivores determines their response, by decreasing the abundance of herbivores with low movement ability (aphids and pine processionary caterpillars) while altering the behavior (plant selection) of more mobile herbivores (pine weevils). Finally, FFG determines the intensity of mistletoe parasitism effects, folivores being more responsive than sapsuckers. Overall, mistletoe generates non‐trophic interaction linkages in the forest able to modify community structure by becoming a nexus of the entire herbivore community of the pine canopy.

Trait-mediated indirect effects in a natural tidepool system

We demonstrate an apparent trait-mediated indirect interaction (TMII) of predators on primary producers in a natural community by altering prey behavior over short and long time scales. Small predatory sea stars (Leptasterias spp.) caused herbivorous snails (Tegula funebralis) added to rocky intertidal tidepools to quickly flee into refuge microhabitats outside tidepools within days, and this was associated with a 58% increase in microalgal growth after 2 weeks. Similarly, removing sea stars caused snails to increase use of tidepools for 1–10 months. After adding sea stars to tidepools, snails quickly fled and then consistently increased use of refuges outside tidepools for 10 months. This was associated with average increases of 59% for microalgal growth over 1 month and 254% for macroalgal growth over 8 months inside tidepools. In 63 unmanipulated tidepools, densities of sea stars and snails were negatively correlated. High densities of snails were associated with unpalatable algal species and bare rock, while high densities of sea stars were associated with palatable algal species, suggesting that this apparent TMII may have community-level impacts. Though multiple lines of evidence suggest TMIIs were likely operating in this system, it was not possible to experimentally partition the relative contributions of TMIIs and density-mediated indirect interactions (DMIIs), so further caging experiments are necessary to distinguish their relative strengths. Overall, we suggest that predators can benefit primary producers by changing prey behavior even when predators and prey are unrestrained by cages or mesocosms, embedded in complex communities, and observed over multiple time scales.

Fish predators reduce kelp frond loss via a trait-mediated trophic cascade.

Although trophic cascades were originally believed to be driven only by predators eating prey, there is mounting evidence that such cascades can be generated in large part via non-consumptive effects. This is especially important in cascades affecting habitat-forming foundation species that in turn, influence associated communities. Here, we use laboratory and field experiments to identify a trait-mediated indirect interaction between predators and an abundant kelp in a marine temperate reef system. Predation risk from a microcarnivorous fish, the señorita, suppressed grazing by the host-specific seaweed limpet, which in turn, influenced frond loss of the habitat-forming feather boa kelp. This trophic cascade was pronounced because minor amounts of limpet grazing decreased the strength required to break kelp fronds. Cues from fish predators mitigated kelp loss by decreasing limpet grazing; we found 86% of this indirect interaction between predator and kelp was attributed to the non-consumptive effect in the laboratory and 56% when applying the same effect size calculations to the field. In field manipulations, the non-consumptive effect of señorita was as strong as the total predator effect and most importantly, as strong as the uncaged, "open" treatment with natural levels of predators. Our findings demonstrate that the mere presence of this fish reduces frond loss of the feather boa kelp through a trait-mediated trophic cascade. Moreover, despite large volumes of water, current flow, and wave energy, we clearly demonstrate a strong non-consumptive effect via an apparent chemical cue from señorita, suggesting that chemically mediated trait-driven cascades may be more prevalent in subtidal marine systems than we are currently aware.

Ecosystem engineering strengthens bottom-up and weakens top-down effects via trait-mediated indirect interactions.

Trophic interactions and ecosystem engineering are ubiquitous and powerful forces structuring ecosystems, yet how these processes interact to shape natural systems is poorly understood. Moreover, trophic effects can be driven by both density- and trait-mediated interactions. Microcosm studies demonstrate that trait-mediated interactions may be as strong as density-mediated interactions, but the relative importance of these pathways at natural spatial and temporal scales is underexplored. Here, we integrate large-scale field experiments and microcosms to examine the effects of ecosystem engineering on trophic interactions while also exploring how ecological scale influences density- and trait-mediated interaction pathways. We demonstrate that (i) ecosystem engineering can shift the balance between top-down and bottom-up interactions, (ii) such effects can be driven by cryptic trait-mediated interactions, and (iii) the relative importance of density- versus trait-mediated interaction pathways can be scale dependent. Our findings reveal the complex interplay between ecosystem engineering, trophic interactions, and ecological scale in structuring natural systems.

Density-mediated indirect effects from active predators and narrow habitat domain prey.

The hunting-mode-habitat-domain-range framework suggests that the mechanism driving trophic cascades (i.e., trait-mediated indirect interactions [TMIIs] vs. density-mediated indirect interactions [DMIIs]) should depend upon the functional traits of predators and prey. For example, trophic cascades containing active, broad habitat domain range (BHDR) predators interacting with narrow habitat domain range (NHDR) prey are predicted to arise primarily via TMIIs, because these prey should reduce their conspicuous activity in the presence of these predators. Unfortunately, this hypothesis is difficult to test given the strong bias against studies assessing trophic cascades containing NHDR prey. Furthermore, this hypothesis ignores evidence that (1) active predators can have high consumption rates on prey, (2) continuously responding to active predators foraging across broad areas is energetically costly for prey, and (3) cues from active, BHDR predators may not influence prey density. We examined the TMIIs and total indirect interaction (TII) produced during interactions between an active, BHDR ladybeetle predator (Naemia seriata) and its NHDR prey (scale insects). We exposed scale insects to nonlethal and lethal ladybeetle predators in laboratory mesocosms for 15 weeks. We measured the growth of the scale insect's host plant (cordgrass) and the population density of scale insects. Contrary to theory, nonlethal ladybeetles did not induce TMIIs. However, lethal ladybeetles increased cordgrass total and root dry biomass by 36% and 44%, respectively, suggesting the presence of strong DMIIs. Additionally, both lethal and nonlethal ladybeetles reduced scale insect population density. Our findings suggest that DMIIs, rather than TMIIs, can result from interactions between active BHDR predators and NHDR prey.

Ecological complexity and agroecosystems: seven themes from theory

ABSTRACTExploring the intersection of new ideas of ecological complexity with insights from traditional agricultural systems is the fundamental subject of this article, with an emphasis on seven themes of ecological complexity, as reflecting contemporary themes in ecology. The seven themes are as follows: 1) turing processes and spatial structure, 2) chaotic dynamics, 3) stochastic processes, 4) coupled oscillators, 5) multidimensionality, 6) trait-mediated indirect interactions, and 7) critical transitions (catastrophe theory). We suggest that these themes of complexity naturally integrate to form one qualitative whole that could be considered a single subject—ecological complexity.

Moving beyond linear food chains: trait-mediated indirect interactions in a rocky intertidal food web.

In simple, linear food chains, top predators can have positive indirect effects on basal resources by causing changes in the traits (e.g. behaviour, feeding rates) of intermediate consumers. Although less is known about trait-mediated indirect interactions (TMIIs) in more complex food webs, it has been suggested that such complexity dampens trophic cascades. We examined TMIIs between a predatory crab (Carcinus maenas) and two ecologically important basal resources, fucoid algae (Ascophyllum nodosum) and barnacles (Semibalanus balanoides), which are consumed by herbivorous (Littorina littorea) and carnivorous (Nucella lapillus) snails, respectively. Because crab predation risk suppresses snail feeding rates, we hypothesized that crabs would also shape direct and indirect interactions among the multiple consumers and resources. We found that the magnitude of TMIIs between the crab and each resource depended on the suite of intermediate consumers present in the food web. Carnivorous snails (Nucella) transmitted TMIIs between crabs and barnacles. However, crab-algae TMIIs were transmitted by both herbivorous (Littorina) and carnivorous (Nucella) snails, and these TMIIs were additive. By causing Nucella to consume fewer barnacles, crab predation risk allowed fucoids that had settled on or between barnacles to remain in the community. Hence, positive interactions between barnacles and algae caused crab-algae TMIIs to be strongest when both consumers were present. Studies of TMIIs in more realistic, reticulate food webs will be necessary for a more complete understanding of how predation risk shapes community dynamics.

Roles of the seasonal dynamics of ecosystem components in fluctuating indirect interactions on a rocky shore.

Accurately evaluating the strengths of direct (i.e., consumptive and non-consumptive) effects and indirect (density- and trait-mediated) interactions is crucial for understanding the mechanisms of the maintenance and dynamics of an ecosystem. However, an in situ evaluation has not been conducted for a long enough period of time to fully consider the seasonality and life histories of the community components. We conducted a 9-month (from summer to spring) field experiment in an intertidal rocky shore ecosystem involving the carnivorous snail, Thais clavigera, its prey, the limpet Siphonaria sirius, and their resources, the cyanobacterium (blue-green alga) Lithoderma sp. and the green algae Ulva spp. From summer to autumn, the predation pressure was high, and the consumptive and non-consumptive effects of the predator had opposite (positive and negative, respectively) effects on the prey. Both the density- and trait-mediated indirect interactions decreased the coverage of Lithoderma and increased the coverage of Ulva. As the predation pressure decreased in autumn, the predator affected both the adults and the new recruits of the prey. The trait-mediated interactions still existed, but the density-mediated interactions were not detected. From winter to spring, no direct effects or indirect interactions were detected because of the low predation pressure. Our investigation highlights previously unnoticed processes-showing that the strengths of the direct effects and indirect interactions fluctuate greatly with the seasonality of the ecosystem components.

生态系统基于性状调节的物种间接作用:特征、成因及后果

PDF HTML阅读 XML下载 导出引用 引用提醒 生态系统基于性状调节的物种间接作用:特征、成因及后果 DOI: 10.5846/stxb201610011986 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31230012）；国家科技基础性工作专项（2012FY111900）；教育部创新团队发展计划（IRT-16R11）；中国博士后面上基金（2016M590246） Characteristics, causes, and consequences of trait-mediated indirect interactions in ecosystems Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:物种之间的间接作用关系是维持生物群落结构以及生态系统功能的关键因素。目前的理论模型和实验性研究均认为，物种间接作用的传递主要是由物种的密度变化所引起。但大量的实验证据表明，生物个体在形态、生理、行为和生活史性状的适应性变化，是物种间形成间接互作关系的另一个重要机制。生态学家把这种基于物种性状调控的种间关系称为性状调节的间接作用。深入了解性状调节的间接作用类型，发生机制和作用途径，有助于阐释自然界中多物种种间关系的复杂性和多样性形成机制。对性状调节的概念和性状的分类进行系统的总结，指出性状可塑性和物种特异性是物种间性状调节关系形成的两个重要机制。与其他类型的种间互作一样，性状调节的种间作用是驱动物种进化的重要力量。此外，分析了性状调节在自然群落中传递的几个重要途径，并强调这些间接作用在影响和调节生态系统功能和过程中的重要作用。最后，就性状调节种间关系的研究对象、研究尺度、以及研究方法等问题提出若干建议，为今后对这一问题的研究提供相关参考。 Abstract:Indirect species interactions play a critical role in shaping community structure and the functioning of ecosystems. Previous empirical and theoretical studies commonly assumed that indirect interactions were caused in general by changes in population density of interacting species, which is referred to as ‘density-mediated indirect interactions.’ However, there is growing evidence that changes in traits of the individual intermediate species can also be an important mechanism that regulates indirect interactions among species, and ecologists term these species interactions ‘trait-mediated indirect interactions’ (TMⅡs). TMⅡs are prevalent in both aquatic and terrestrial systems, and their effects are often as strong as, or stronger than, those of density-mediated indirect effects. Studies on the characteristics, causes, and consequences of TMⅡs are essential to understand the complexity and diversity of multispecies interactions in natural ecosystems fully. In this paper, we summarize the concept and classification of TMⅡs, and suggest that trait plasticity and species specificity are the two intrinsic mechanisms for the occurrence of TMⅡs. We also review the direct evidence for TMⅡs in various permutations of interaction webs that can have both trophic and non-trophic links, and then highlight the profound effects of TMⅡs on regulation of ecological functions and processes in a wide range of ecological systems. Finally, we propose future developments regarding the effects of TMⅡs to provide a reference framework for related research. 参考文献 相似文献 引证文献

A Discrete Predator-Prey Ecoepidemic Model

In this work we present a discrete predator-prey ecoepidemic model. The predator-prey interactions are represented by a discrete Leslie-Gower model with prey intra-specific competition. The disease dynamics follows a discrete SIS epidemic model with frequency-dependent transmission. We focus on the case of disease only affecting prey though the case of a parasite of the predators is also presented. We assume that parasites provoke density- and trait-mediated indirect interactions in the predator-prey community that occur on a shorter time scale. This is included in the model considering that in each time unit there exist a number k of episodes of epidemic changes followed by a single episode of demographic change, all of them occurring separately. The aim of this work is examining the effects of parasites on the long-term prey-predators interactions. These interactions in the absence of disease are governed by the Leslie-Gower model. In the case of endemic disease they can be analyzed through a reduced predator-prey model which summarizes the disease dynamics in its parameters. Conditions for the disease to drive extinct the whole community are obtained. When the community keeps stabilized different cases of the influence of disease on populations sizes are presented.

Trait-mediated indirect interactions of ant shape on the attack of caterpillars and fruits.

Mainly owing to their high diversity and abundance, ants are formidable as predators and defenders of foliage. Consequently, ants can exclude both invertebrate and vertebrate activity on plants via direct and indirect interactions as already shown in many previous studies. Here we present empirical evidence that objects resembling ant shape on dummy caterpillars were able to repel visually oriented predators. Moreover, we also show that rubber ants on dummy fruits can repel potential fruit dispersers. Our results have direct implications on the ecological and evolutionary dynamics of interactions in ant-based systems, as ant presence could affect the fitness of its partners. In short, our study highlights the importance of visual cues in interspecific interactions and opens a new way to study the effects of ant presence to test ecological and evolutionary hypotheses.

Fear and below-ground food-webs

Predator induced trait mediated indirect interactions (TMIIs) are likely the dominant facet of trophic interactions in aboveground food-webs. New research is beginning to show that TMIIs are also important in revealing how soil food-webs (SFWs) regulate biogeochemical processes. We suggest that TMIIs can modify SFW functions by (a) regulating the quantity and nutritional quality of plants and animal production known to drive the SFW, (b) inducing defense phenotypes in soil-organisms, and (c) changing soil environmental conditions. Currently, very few studies have explored the role TMIIs play in shaping SFW functions, especially the cascading effects on SFW dynamics. Much theoretical and empirical research is needed before we can successfully incorporate the non-consumptive effects of predation into SFW models.