Host functional and phylogenetic composition rather than host diversity structure plant–herbivore networks

Declining plant diversity alters ecological networks, such as plant–herbivore interactions. However, our knowledge of the potential mechanisms underlying effects of plant species loss on plant–herbivore network structure is still limited. We used DNA barcoding to identify herbivore–host plant associations along declining levels of tree diversity in a large‐scale, subtropical biodiversity experiment. We tested for effects of tree species richness, host functional and phylogenetic diversity, and host functional (leaf trait) and phylogenetic composition on species, phylogenetic and network composition of herbivore communities. We found that phylogenetic host composition and related palatability/defence traits but not tree species richness significantly affected herbivore communities and interaction network complexity at both the species and community levels. Our study indicates that evolutionary dependencies and functional traits of host plants determine the composition of higher trophic levels and corresponding interaction networks in species‐rich ecosystems. Our findings highlight that characteristics of the species lost have effects on ecosystem structure and functioning across trophic levels that cannot be predicted from mere reductions in species richness.     

The tri‐trophic niche concept and adaptive radiation of phytophagous insects

A conceptual divide exists between ecological and evolutionary approaches to understanding adaptive radiation, although the phenomenon is inherently both ecological and evolutionary. This divide is evident in studies of phytophagous insects, a highly diverse group that has been frequently investigated with the implicit or explicit goal of understanding its diversity. Whereas ecological studies of phytophagous insects increasingly recognize the importance of tri‐trophic interactions as determinants of niche dimensions such as host‐plant associations, evolutionary studies typically neglect the third trophic level. Here we attempt to reconcile ecological and evolutionary approaches through the concept of the ecological niche. We specifically present a tri‐trophic niche concept as a foil to the traditional bi‐trophic niche concept for phytophagous insects. We argue that these niche concepts have different implications for understanding herbivore community structure, population divergence, and evolutionary diversification. To this end, we offer contrasting empirical predictions of bi‐ and tri‐trophic niche concepts for patterns of community structure, the process of population divergence, and patterns of evolutionary diversification of phytophagous insects.     

Genetic factors affecting food‐plant specialization of an oligophagous seed predator

Several ecological and genetic factors affect the diet specialization of insect herbivores. The evolution of specialization may be constrained by lack of genetic variation in herbivore performance on different food‐plant species. By traditional view, trade‐offs, that is, negative genetic correlations between the performance of the herbivores on different food‐plant species favour the evolution of specialization. To investigate whether there is genetic variation or trade‐offs in herbivore performance between different food plants that may influence specialization of the oligophagous seed‐eating herbivore, Lygaeus equestris (Heteroptera), we conducted a feeding trial in laboratory using four food‐plant species. Although L. equestris is specialized on Vincetoxicum hirundinaria (Apocynaceae) to some degree, it occasionally feeds on alternative food‐plant species. We did not find significant negative genetic correlations between mortality, developmental time and adult biomass of L. equestris on the different food‐plant species. We found genetic variation in mortality and developmental time of L. equestris on some of the food plants, but not in adult biomass. Our results suggest that trade‐offs do not affect adaptation and specialization of L. equestris to current and novel food‐plant species, but the lack of genetic variation may restrict food‐plant utilization. As food‐plant specialization of herbivores may have wide‐ranging effects, for instance, on coevolving plant–herbivore interactions and speciation, it is essential to thoroughly understand the factors behind the specialization process. Our findings provide valuable information about the role of genetic factors in food‐plant specialization of this oligophagous herbivore.     

Ecological factors associated with the strength of trophic cascades in streams

Trophic cascades are extensively documented in nature, but they are also known to vary widely in strength and frequency across ecosystems. Therefore, much effort has gone into understanding which ecological factors generate variation in cascade strength. To identify which factors covary with the strength of cascades in streams, we performed a concurrent experiment across 17 streams throughout the Sierra Nevada Mountains. We eliminated top consumers from experimental substrates using electrical exclusions and compared the strength of indirect effects of consumers on the biomass of primary producers relative to control patches. In each stream we 1) classified the dominant invertebrate herbivores according to life‐history traits that influence their susceptibility to predators, 2) determined the abundance and diversity of algae and herbivores, and 3) measured production‐to‐biomass ratios (P:B) of the stream biofilm. This allowed us to assess three common predictions about factors thought to influence the strength of trophic cascades: cascade strength 1) is weaker in systems dominated by herbivores with greater ability to evade or defend against predators, 2) is stronger in systems characterized by low species diversity, and 3) increases with increasing producer P:B. When averaged across all streams, the indirect effect of predators increased the biomass of periphyton by a mean 60%. However, impacts of predators on algae varied widely, ranging from effects that exacerbated algal loss to herbivores, to strong cascades that increased algal biomass by 4.35 times. Cascade strength was not related to herbivore traits or species diversity, but decreased significantly with increasing algal diversity and biofilm P:B in a stream. Partial regression analyses suggested that the relationship between cascade strength and algal diversity was spurious, and that the only significant covariate after statistically controlling for cross‐correlations was algal P:B. Our study contributes to the ongoing debate about why trophic cascade strength varies in nature and is useful because it eliminates factors that have no potential to explain variation in cascades within these stream ecosystems.     

Predators,fire or resources: What drives the distribution of herbivores in fragmented mesic forests?

Trophic interactions and disturbance events can shape the structure and function of ecosystems. However, the effects of drivers such as predation, fire and climatic variables on species distributions are rarely considered concurrently. We used a replicated landscape‐scale predator management experiment to compare the effects of red fox Vulpes vulpes control, time‐since‐fire, vegetation type and other environmental variables on native herbivore distributions. Occurrence data for four native herbivores and an invasive predator – the red fox – were collected from 240 sites across three baited (for lethal fox control) and three unbaited forest blocks (4659–9750 ha) in south‐western Victoria, Australia, and used to build species distribution models. The herbivore taxa were as follows: red‐necked wallaby Macropus rufogriseus, black wallaby Wallabia bicolour, grey kangaroo Macropus fuligenosus and Macropus giganteus and common brushtail possum Trichosurus vulpecula. Fox control and fire had little effect on herbivore occurrence, despite the literature suggesting it can influence abundance, while climate, proximity to farmland and topography were more influential. This may be because the region’s high productivity and agricultural pastures subsidise food resources for both predators and prey within the forest blocks and so dampen trophic interactions. Alternatively, these drivers may affect herbivore abundance, but not herbivore occurrence. Understanding the drivers of herbivore distributions is an important step in predicting the effects of herbivory on other species, particularly after management interventions such as predator control and prescribed burns.     

Effects of environmental stress cascade up through four trophic levels in a salt marsh study system

1. Although in recent years there have been a number of studies demonstrating trophic cascades in terrestrial systems, it is still unclear what environmental conditions enable or enhance such cascades, especially among four trophic levels. 2. In this study, the influence of environmental stress (increased soil pore water salinity) on a four trophic level study system in a Florida salt marsh was examined by experimentally increasing soil pore water salinity. Effects of increased salinity on the quality of the host plant, Batis maritima, were assessed, as were resulting effects on the lepidopteran herbivore Ascia monuste, and the primary parasitoids and hyperparasitoids of its caterpillars. 3. Increased salinity altered host‐plant quality, which subsequently affected the consumer species. These effects of altered plant quality cascaded up through the herbivore and primary parasitoid to the hyperparasitoid Hypopteromalus inimicus, influencing its density, sex ratio, body size, and initial egg load. 4. These results demonstrate how heterogeneity in environmental stress can result in effects that cascade up through four trophic levels. We suggest that such strong effects at higher trophic levels may be more likely in systems in which relationships are more specific and intimate such as those among hosts, parasitoids, and hyperparasitoids.     

Seasonality and interspecific competition shape individual niche variation in co‐occurring tetra fish in Neotropical streams

The drivers of intraspecific niche variation and its effects on species interactions are still unclear, especially in species‐rich Neotropical environments. Here, we investigated how ecological opportunity and interspecific competition affect the degree of individual trophic specialization and the population niche breadth in tetra fish. We studied the four ecologically similar species (Psalidodon aff. gymnodontus, P. aff. paranae, P. bifasciatus, and Bryconamericus ikaa) in subtropical headwater streams (three sites with two co‐occurring species and three sites with only one species). We sampled fish in two contrasting seasons (winter/dry and summer/wet) and quantified their trophic niches using gut content analysis. Psalidodon bifasciatus was the only species distributed over all the sampled streams. We observed seasonal differences in population trophic niche breadth of P. bifasciatus just when this species co‐occurred with P. aff. gymnodontus. These findings confirm the complex nature of the effects of interspecific competition, depending, for instance, on the identity of the competitor. The degree of individual specialization of P. bifasciatus was higher in the winter, and it was not influenced by the presence of another species. Conversely, the other two Psalidodon species studied presented greater individual specialization in the summer, when fish consumed a higher proportion of allochthonous items (terrestrial insects and seeds), and there were no effects only for B. ikaa. Herein, our results suggest that seasonality in food‐resource availability is a major driver of niche variation and it has the potential to play an important role in how these similar tetra species interact and coexist. Abstract in Portuguese is available with online material.     

Context-dependent defence in terrestrial plants: the effects of light and nutrient availability on plant resistance against herbivory

The context‐dependent defence (CDD) hypothesis predicts that defence levels of plant species against herbivory are not fixed but vary with environmental conditions, in a way that is specific for plant species that share evolutionary adaptations to resource conditions exemplified by similar maximum relative growth rates. More specifically, we expected plants from resource‐poor environments to display high defence levels but not when grown under resource‐rich conditions, whereas the reverse – plants from resource‐rich conditions displaying low defence levels but not when grown under resource‐poor conditions – is not necessarily the case. In this study, we used multiple‐choice bioassays in which leaf discs were fed to larvae of Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) as an efficient and effective way of indicating plant defence levels. This generalist herbivore was capable of detecting both inter‐ and intraspecific differences in defence among plant species. The CDD was tested by exploring the effects of various experimental resource conditions (light, nutrients) upon the herbivore preferences and by comparing these preferences with the maximum relative growth rate of plant species. The experimental results provide general support for the CDD hypothesis with respect to nutrient‐level variation but the effects were not related to the origin of the plant species tested. Variation in light conditions did not result in consistent effects upon herbivore preferences. The CDD therefore can be formulated more precisely as: defence levels of plant species vary under different environmental conditions but in a way that is specific for plant species that share evolutionary adaptations to similar nutrient conditions. This more precise CDD hypothesis is a useful addition to existing optimal‐defence theory because of its focus on the possible plastic effects of resource conditions upon plant defence levels. This is relevant when designing experimental plant–herbivore studies.     

Phenotypic variation and genomic variation in insect virulence traits reveal patterns of intraspecific diversity in a locust-specific fungal pathogen

Intraspecific pathogen diversity is crucial for understanding the evolution and maintenance of adaptation in host–pathogen interactions. Traits associated with virulence are often a significant source of variation directly impacted by local selection pressures. The specialist fungal entomopathogen, Metarhizium acridum, has been widely implemented as a biological control agent of locust pests in tropical regions of the world. However, few studies have accounted for natural intraspecific phenotypic and genetic variation. Here, we examine the diversity of nine isolates of M. acridum spanning the known geographic distribution, in terms of (1) virulence towards two locust species, (2) growth rates on three diverse nutrient sources, and (3) comparative genomics to uncover genomic variability. Significant variability in patterns of virulence and growth was shown among the isolates, suggesting intraspecific ecological specialization. Different patterns of virulence were shown between the two locust species, indicative of potential host preference. Additionally, a high level of diversity among M. acridum isolates was observed, revealing increased variation in subtilisin-like proteases from the Pr1 family. These results culminate in the first in-depth analysis regarding multiple facets of natural variation in M. acridum, offering opportunities to understand critical evolutionary drivers of intraspecific diversity in pathogens.     

Resource composition mediates the effects of intraspecific variability in nutrient recycling on ecosystem processes

Despite the growing evidence for individual variation in trophic niche within populations, its potential indirect effects on ecosystem processes remains poorly understood. In particular, few studies have investigated how intraspecific trophic variability can modulate the effects of consumers on ecosystems through potential changes in nutrient excretion rates. Here, we first quantified the level of intraspecific trophic variability in 11 wild populations of the omnivorous fish Lepomis gibbosus. Outputs from stomach content and stable isotope analyses revealed that the degree of trophic specialization and trophic positions were highly variable between and within these wild populations. There was intrapopulation variation in trophic position of more than one trophic level, suggesting that individuals consumed a range of plant and animal resources. We then experimentally manipulated intraspecific trophic variability to assess how it can modulate consumer‐mediated nutrient effects on relevant processes of ecosystem functioning. Specifically, three food sources varying in nutrient quality (e.g. plant material, macro‐invertebrate and fish meat) were used individually or in combination to simulate seven diet treatments. Results indicated that intraspecific variability in growth and nitrogen excretion rates were more related to the composition of the diet rather than the degree of specialization, and increased with the trophic position of the diet consumed. We subsequently used microcosms and showed that critical ecosystem functions, such as primary production and community respiration, were affected by the variability in excretory products, and this effect was biomass‐dependent. These results highlight the importance of considering variation within species to better assess the effects of individuals on ecosystems and, more specifically, the effects of consumer‐mediated nutrient recycling because the body size and the trophic ecology of individuals are affected by a large spectrum of natural and human‐induced environmental changes.     

The ancient lakes of Indonesia: towards integrated research on speciation

Ancient lakes have provided considerable insights into the drivers of speciation and adaptive radiation in aquatic organisms. Most studies of species-flocks, however, focus only on a single group of organisms, and few have attempted to integrate geological, limnological, ecological, and genetic drivers of speciation on multiple species-flocks at various trophic levels. As such, there is a need for a comprehensive model system for research on speciation in aquatic environments where multiple radiations are investigated at various levels of biological organization (e.g., individual, population, and ecosystem) and placed in light of geographical and geological setting. The ancient Malili Lakes of Sulawesi, Indonesia, are ideal candidates for such a model, and represent the only hydrologically connected ancient lakes in the world. These lakes are characterized by ultra-oligotrophy and unique physicochemical conditions that govern the composition and production of planktonic communities. At higher trophic levels, there are three recurring trends: (1) low taxonomic richness and simple community structures, (2) adaptive radiations with trophic specialization, and (3) remarkably high endemism with evolutionary innovations throughout the lakes and species-flocks. Furthermore, the restricted geographic distributions of species-flocks within the Malili Lakes indicate that each lake constitutes a unique environment, and dispersal among lakes is limited, despite close contemporary connectivity. These observations suggest that ecological and evolutionary processes are regulated from the bottom up, and speciation is primarily facilitated by interspecific and intraspecific competition for limited resources. The Malili Lakes represent an outstanding natural model for integrative research into speciation as they offer the opportunity to explore the roles of geography, dispersal, and selection in the radiation of aquatic organisms.     

Herbivore species richness, composition and community structure mediate predator richness effects and top-down control of herbivore biomass

Changes in predator species richness can have important consequences for ecosystem functioning at multiple trophic levels, but these effects are variable and depend on the ecological context in addition to the properties of predators themselves. Here, we report an experimental study to test how species identity, community attributes, and community structure at the herbivore level moderate the effects of predator richness on ecosystem functioning. Using mesocosms containing predatory insects and aphid prey, we independently manipulated species richness at both predator and herbivore trophic levels. Community structure was also manipulated by changing the distribution of herbivore species across two plant species. Predator species richness and herbivore species richness were found to negatively interact to influence predator biomass accumulation, an effect which is hypothesised to be due to the breakdown of functional complementarity among predators in species-rich herbivore assemblages. The strength of predator suppression of herbivore biomass decreased as herbivore species richness and distribution across host plants increased, and positive predator richness effects on herbivore biomass suppression were only observed in herbivore assemblages of relatively low productivity. In summary, the study shows that the species richness, productivity and host plant distribution of prey communities can all moderate the general influence of predators and the emergence of predator species richness effects on ecosystem functioning.     

Geographic host use variability and host range evolutionary dynamics in the phytophagous insect <Emphasis Type="Italic">Apagomerella versicolor</Emphasis> (Cerambycidae)

The high diversity of phytophagous insects has been explained by the tendency of the group towards specialization; however, generalism may be advantageous in some environments. The cerambycid Apagomerella versicolor exhibits intraspecific geographical variation in host use. In northern Argentina it is highly specialized on the herb Pluchea sagittalis (Asteraceae), while in central and southern areas it uses seven Asteraceae species. To study host species geographical variation from ecological and evolutionary perspectives, we investigated field host availability and use across a wide latitudinal range, and performed laboratory studies on insect oviposition preference and larval performance and mitochondrial DNA (mtDNA) variation in a phylogeographical framework. Geographic variation in host use was unrelated to host availability but was highly associated with laboratory oviposition preference, larval performance, and mtDNA variation. Genetic studies revealed three geographic races of A. versicolor with gene flow restriction and recent geographic expansion. Trophic generalism and oligophagy within A. versicolor seem to have evolved as adaptations to seasonal and spatial unavailability of the preferred host P. sagittalis in cooler areas of the species’ geographic range. No single genotype is successful in all environments; specialization may be advantageous in environments with uniform temporal and spatial host availability, while being a trophic generalist may provide an adaptive advantage in host-constrained environments.     

Determinants of parasitoid communities of willow‐galling sawflies: habitat overrides physiology,host plant and space

Studies on the determinants of plant–herbivore and herbivore–parasitoid associations provide important insights into the origin and maintenance of global and local species richness. If parasitoids are specialists on herbivore niches rather than on herbivore taxa, then alternating escape of herbivores into novel niches and delayed resource tracking by parasitoids could fuel diversification at both trophic levels. We used DNA barcoding to identify parasitoids that attack larvae of seven Pontania sawfly species that induce leaf galls on eight willow species growing in subarctic and arctic–alpine habitats in three geographic locations in northern Fennoscandia, and then applied distance‐ and model‐based multivariate analyses and phylogenetic regression methods to evaluate the hierarchical importance of location, phylogeny and different galler niche dimensions on parasitoid host use. We found statistically significant variation in parasitoid communities across geographic locations and willow host species, but the differences were mainly quantitative due to extensive sharing of enemies among gallers within habitat types. By contrast, the divide between habitats defined two qualitatively different network compartments, because many common parasitoids exhibited strong habitat preference. Galler and parasitoid phylogenies did not explain associations, because distantly related arctic–alpine gallers were attacked by a species‐poor enemy community dominated by two parasitoid species that most likely have independently tracked the gallers’ evolutionary shifts into the novel habitat. Our results indicate that barcode‐ and phylogeny‐based analyses of food webs that span forested vs. tundra or grassland environments could improve our understanding of vertical diversification effects in complex plant–herbivore–parasitoid networks.     

Differences in evolutionary history translate into differences in invasion success of alien mammals in South Africa

Attempts to investigate the drivers of invasion success are generally limited to the biological and evolutionary traits distinguishing native from introduced species. Although alien species introduced to the same recipient environment differ in their invasion intensity – for example, some are “strong invaders”; others are “weak invaders” – the factors underlying the variation in invasion success within alien communities are little explored. In this study, we ask what drives the variation in invasion success of alien mammals in South Africa. First, we tested for taxonomic and phylogenetic signal in invasion intensity. Second, we reconstructed predictive models of the variation in invasion intensity among alien mammals using the generalized linear mixed‐effects models. We found that the family Bovidae and the order Artiodactyla contained more “strong invaders” than expected by chance, and that such taxonomic signal did not translate into phylogenetic selectivity. In addition, our study indicates that latitude, gestation length, social group size, and human population density are only marginal determinant of the variation in invasion success. However, we found that evolutionary distinctiveness – a parameter characterising the uniqueness of each alien species – is the most important predictive variable. Our results indicate that the invasive behavior of alien mammals may have been “fingerprinted” in their evolutionary past, and that evolutionary history might capture beyond ecological, biological and life‐history traits usually prioritized in predictive modeling of invasion success. These findings have applicability to the management of alien mammals in South Africa.     

A cascade of evolutionary change alters consumer-resource dynamics and ecosystem function

It is becoming increasingly clear that intraspecific evolutionary divergence influences the properties of populations, communities and ecosystems. The different ecological impacts of phenotypes and genotypes may alter selection on many species and promote a cascade of ecological and evolutionary change throughout the food web. Theory predicts that evolutionary interactions across trophic levels may contribute to hypothesized feedbacks between ecology and evolution. However, the importance of 'cascading evolutionary change' in a natural setting is unknown. In lakes in Connecticut, USA, variation in migratory behaviour and feeding morphology of a fish predator, the alewife (Alosa pseudoharengus), drives life-history evolution in a species of zooplankton prey (Daphnia ambigua). Here we evaluated the reciprocal impacts of Daphnia evolution on ecological processes in laboratory mesocosms. We show that life-history evolution in Daphnia facilitates divergence in rates of population growth, which in turn significantly alters consumer-resource dynamics and ecosystem function. These experimental results parallel trends observed in lakes. Such results argue that a cascade of evolutionary change, which has occurred over contemporary timescales, alters community and ecosystem processes.     

Keystone mutualism influences forest tree growth at a landscape scale

Interactions between ants and phloem‐feeding herbivores are characterised as a keystone mutualism because they restructure arthropod communities and generate trophic cascades. Keystone interactions in terrestrial food webs are hypothesised to depend on herbivore community structure and bottom‐up effects on plant growth. Here, we tested this prediction at a landscape scale with a long‐term ant‐exclusion experiment on hickory saplings in the context of spatial variation in herbivore community structure and habitat quality. We quantified top‐down effects of ants, herbivore communities as well as abiotic factors impacting hickory shoot growth. We found that ants influenced shoot growth via strong, context‐dependent, compensatory effects, with clear cascading benefits only when phloem‐feeders were present and chewing herbivore abundance was high. By contrast, while several landscape variables predicted hickory growth, they did not mediate the strength of cascading effects of ants. These results suggest that ant/sap‐feeder mutualisms may regulate forest productivity by mediating effects of multiple herbivore guilds.     

The genetics of chutes and ladders: a community genetics approach to tritrophic interactions

Community genetics research has firmly established that intraspecific genetic variation in single populations can have large extended ecological consequences for populations and entire communities of organisms. Here, we sought to understand the bottom‐up effects of plant genetic variation on herbivore preference and performance, and the top–down control of predators on herbivores and their joint effects on plant fitness and evolution. Following three ecological genetics field experiments we detected heritable variation in plant traits that influenced both the preference and performance of a specialist weevil on Oenothera biennis. However, the weevil's preference and performance were not genetically correlated among O. biennis plant genotypes. Although predators and parasitoids were abundant, predators had no detectable effect on weevil performance because high egg and larval mortality was caused by non‐predatory factors such as intraspecific competition. Finally, neither the specialist weevil nor predators influenced plant fitness. Our results suggest that the focal tritrophic community studied here is primarily shaped by the bottom–up effects of plant genetic variation on herbivores, while top–down effects have no clear impacts on O. biennis fitness or evolution. We suggest that future studies should incorporate plant intraspecific genetic variation as a fundamental part of tritrophic interactions including their eco‐evolutionary dynamics.     

Evolutionary response when selection and genetic variation covary across environments

Although models of evolution usually assume that the strength of selection on a trait and the expression of genetic variation in that trait are independent, whenever the same ecological factor impacts both parameters, a correlation between the two may arise that accelerates trait evolution in some environments and slows it in others. Here, we address the evolutionary consequences and ecological causes of a correlation between selection and expressed genetic variation. Using a simple analytical model, we show that the correlation has a modest effect on the mean evolutionary response and a large effect on its variance, increasing among‐population or among‐generation variation in the response when positive, and diminishing variation when negative. We performed a literature review to identify the ecological factors that influence selection and expressed genetic variation across traits. We found that some factors – temperature and competition – are unlikely to generate the correlation because they affected one parameter more than the other, and identified others – most notably, environmental novelty – that merit further investigation because little is known about their impact on one of the two parameters. We argue that the correlation between selection and genetic variation deserves attention alongside other factors that promote or constrain evolution in heterogeneous landscapes.     

Causes and consequences of ontogenetic dietary shifts: a global synthesis using fish models

Ontogenetic dietary shifts (ODSs), the changes in diet utilisation occurring over the life span of an individual consumer, are widespread in the animal kingdom. Understanding ODSs provides fundamental insights into the biological and ecological processes that function at the individual, population and community levels, and is critical for the development and testing of hypotheses around key concepts in trophic theory on model organisms. Here, we synthesise historic and contemporary research on ODSs in fishes, and identify where further research is required. Numerous biotic and abiotic factors can directly or indirectly influence ODSs, but the most influential of these may vary spatially, temporally and interspecifically. Within the constraints imposed by prey availability, we identified competition and predation risk as the major drivers of ODSs in fishes. These drivers do not directly affect the trophic ontogeny of fishes, but may have an indirect effect on diet trajectories through ontogenetic changes in habitat use and concomitant changes in prey availability. The synthesis provides compelling evidence that ODSs can have profound ecological consequences for fish by, for example, enhancing individual growth and lifetime reproductive output or reducing the risk of mortality. ODSs may also influence food‐web dynamics and facilitate the coexistence of sympatric species through resource partitioning, but we currently lack a holistic understanding of the consequences of ODSs for population, community and ecosystem processes and functioning. Studies attempting to address these knowledge gaps have largely focused on theoretical approaches, but empirical research under natural conditions, including phylogenetic and evolutionary considerations, is required to test the concepts. Research focusing on inter‐individual variation in ontogenetic trajectories has also been limited, with the complex relationships between individual behaviour and environmental heterogeneity representing a particularly promising area for future research.