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The mathematical theory describing small assemblages of interacting species (community modules or motifs) has significantly improved our understanding of the emergent properties of ecological communities. It is not clear whether all interactions accounted for in such models will be realized in real communities.Here, we use community modules to experimentally explore whether the number of trophic links among species scales with community complexity (i.e. by adding species known to feed on each other from pairwise trials) in a simple mite community present in avocado orchards (Persea americana). By varying the presence of each of two predators (Euseius stipulatus and Neoseiulus californicus), one herbivore as shared prey (Oligonychus perseae) and pollen of Carpobrotus edulis as an alternative food resource, we mimicked communities with simple trophic chains, intraguild predation and/or apparent competition. We then assessed predation rates and the conversion of food into offspring in those communities.We found that increasing the number of potential interactions did not result in more complex realized community modules. Instead, all species effectively fed upon a single food item, hence all community modules actually corresponded to one or two linear trophic chains.Therefore, trophic links assumed to occur when species are assembled in pairs do not necessarily occur when other components of the community are present. Consequently, food web structure may be much less complex than predicted by theory. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Prey refuges are expected to affect population dynamics, but direct experimental tests of this hypothesis are scarce. Larvae of western flower thrips Frankliniella occidentalis use the web produced by spider mites as a refuge from predation by the predatory mite Neoseiulus cucumeris. Thrips incur a cost of using the refuge through reduced food quality within the web due to spider mite herbivory, resulting in a reduction of thrips developmental rate. These individual costs and benefits of refuge use were incorporated in a stage-structured predator–prey model developed for this system. The model predicted higher thrips numbers in presence than in absence of the refuge during the initial phase. A greenhouse experiment was carried out to test this prediction: the dynamics of thrips and their predators was followed on plants damaged by spider mites, either with or without web. Thrips densities in presence of predators were higher on plants with web than on unwebbed plants after 3 weeks. Experimental data fitted model predictions, indicating that individual-level measurements of refuge costs and benefits can be extrapolated to the level of interacting populations. Model-derived calculations of thrips population growth rate enable the estimation of the minimum predator density at which thrips benefit from using the web as a refuge. The model also predicted a minor effect of the refuge on the prey density at equilibrium, indicating that the effect of refuges on population dynamics hinges on the temporal scale considered. [ABSTRACT FROM AUTHOR]

Most studies on eco‐evolutionary feedbacks concern the influence of abiotic factors, or predator–prey and host–parasite interactions, while studies involving sexual interactions are lagging behind. This is at odds with the potential of these interactions to engage in such processes. Indeed, there is now ample evidence that sexual selection is affected by ecological change and that sexually selected traits can evolve rapidly, which may modify the ecological context of populations, and thus the selection pressures they will be exposed to. Here we review evidence for such eco‐evolutionary processes. We discuss examples of eco‐evolutionary change in an attempt to understand the challenges related with identifying and characterizing such processes. In particular, we focus on the challenges associated with accurately identifying the components of the feedback as well as their causal relation. Finally, we evaluate scenarios where understanding eco‐evolutionary feedbacks of sexual selection may help us appreciate the effects of sexual selection in shaping evolutionary processes. [ABSTRACT FROM AUTHOR]

To prevent predation on their eggs, prey often avoid patches occupied by predators. As a result, they need to delay oviposition until they reach predator-free patches. Because many species allocate energy to egg production in a continuous fashion, it is not clear what kind of mechanism prey use to delay oviposition. We used females of the phytoseiid mite Neoseiulus cucumeris to study these mechanisms. Females were placed in patches with pollen, a food source they use for egg production, and they were exposed to another phytoseiid mite, Iphiseius degenerans, which is an intraguild predator of N. cucumeris juveniles. We found that the oviposition of N. cucumeris females on patches with the predator was lower than on patches without the predator. Cues left by the intraguild predator were not sufficient to elicit such behaviour. Females of N. cucumeris reduced oviposition when exposed to the predator by retaining the egg inside their body, resulting in a lower developmental rate once these eggs were laid. Hence, females are capable of retaining eggs, but the development of these eggs continues inside the mother’s body. In this way, females gain some time to search for less risky oviposition sites. [ABSTRACT FROM AUTHOR]

1. Many cannibalistic species are also intra-guild predators. Such predators will often face the decision whether to consume a conspecific or a heterospecific prey from the same guild. This decision may depend on the relative quality and abundance of the prey but also on other factors such as relatedness by descent, prey-specific defence and the probability of the victim harbouring shared diseases. 2. Here, intra-guild interactions among two cannibalistic species of predatory mites, Iphiseius degenerans and Neoseiulus cucumeris (Acari: Phytoseiidae) that belong to closely related genera were studied. 3. Individuals of I. degenerans were offered a diet of conspecifics or heterospecifics. Because I. degenerans is capable of recognising kin individuals from non-kin, and they were exclusively offered conspecifics that were either distantly related or non-kin, it was expected that it would not refrain from cannibalising for reasons of possible relatedness. 4. When corrected for numbers of victims eaten, survival, and juvenile development of predators fed with intra-guild prey was higher than that of cannibals. This was probably caused by a higher quality of heterospecific victims, even though conspecific victims were larger and therefore potentially contained more food. This led to the prediction that the predators should strongly prefer heterospecific prey. This was indeed borne out in independent choice experiments. Thus, the choice of predators between heterospecific and conspecific prey is not only affected by avoidance of consuming conspecifics, but also by relative prey quality. [ABSTRACT FROM AUTHOR]

One of the current challenges in evolutionary ecology is understanding the long-term persistence of contemporary-evolving predator-prey interactions across space and time. To address this, we developed an extension of a multi-locus, multi-trait eco-evolutionary individual-based model that incorporates several interacting species in explicit landscapes. We simulated eco-evolutionary dynamics of multiple species food webs with different degrees of connectance across soil-moisture islands. A broad set of parameter combinations led to the local extinction of species, but some species persisted, and this was associated with (1) high connectance and omnivory and (2) ongoing evolution, due to multi-trait genetic variability of the embedded species. Furthermore, persistence was highest at intermediate island distances, likely because of a balance between predation-induced extinction (strongest at short island distances) and the coupling of island diversity by top predators, which by travelling among islands exert global top-down control of biodiversity. In the simulations with high genetic variation, we also found widespread trait evolutionary changes indicative of eco-evolutionary dynamics. We discuss how the ever-increasing computing power and high-resolution data availability will soon allow researchers to start bridging the in vivo-in silico gap. [ABSTRACT FROM AUTHOR]

Mixed-species associations are temporary associations between individuals of different species that are often observed in birds, primates and cetaceans. They have been interpreted as a strategy to reduce predation risk, enhance foraging success and/or provide a social advantage. In the archipelago of the Azores, four species of dolphins are commonly involved in mixed-species associations: the common dolphin, Delphinus delphis, the bottlenose dolphin, Tursiops truncatus, the striped dolphin, Stenella coeruleoalba, and the spotted dolphin, Stenella frontalis. In order to understand the reasons why dolphins associate, we analysed field data collected since 1999 by research scientists and trained observers placed onboard fishing vessels. In total, 113 mixed-species groups were observed out of 5720 sightings. The temporal distribution, habitat (water depth, distance to the coast), behaviour (i.e. feeding, travelling, socializing), size and composition of mixed-species groups were compared with those of single-species groups. Results did not support the predation avoidance hypothesis and gave little support to the social advantage hypothesis. The foraging advantage hypothesis was the most convincing. However, the benefits of mixed-species associations appeared to depend on the species. Associations were likely to be opportunistic in the larger bottlenose dolphin, while there seemed to be some evolutionary constraints favouring associations in the rarer striped dolphin. Comparison with previous studies suggests that the formation of mixed-species groups depends on several environmental factors, and therefore may constitute an adaptive response. [ABSTRACT FROM AUTHOR]

It is well known that young, small predator stages are vulnerable to predation by conspecifics, intra-guild competitors or hyperpredators. It is less known that prey can also kill vulnerable predator stages that present no danger to the prey. Since adult predators are expected to avoid places where their offspring would run a high predation risk, this opens the way for potential prey to deter dangerous predator stages by killing vulnerable predator stages. We present an example of such a complex predator–prey interaction. We show that (1) the vulnerable stage of an omnivorous arthropod prey discriminates between eggs of a harmless predator species and eggs of a dangerous species, killing more eggs of the latter; (2) prey suffer a minor predation risk from newly hatched predators; (3) adult predators avoid ovipositing near killed predator eggs, and (4) vulnerable prey near killed predator eggs experience an almost fourfold reduction of predation. Hence, by attacking the vulnerable stage of their predator, prey deter adult predators and thus reduce their own predation risk. This provides a novel explanation for the killing of vulnerable stages of predators by prey and adds a new dimension to anti-predator behaviour. [ABSTRACT FROM AUTHOR]