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Understanding Batesian mimicry is a classic problem in evolutionary biology. In Batesian mimicry, a defended species (the model) is mimicked by an undefended species (the mimic). Prior theories have emphasized the role of predator behavior and learning as well as evolution in model-mimic complexes but have not examined the role of population dynamics in potentially governing the relative abundances and even persistence of model-mimic systems. Here, we examined the effect of the population dynamics of predators and alternative prey on the prevalence of warning-signaling prey composed of models and mimics. Using optimal foraging theory and signal detection theory, we found that the inclusion of predator and alternative prey population dynamics could reverse traditional theoretical predictions: as alternative prey increase in numbers, mimics suffer because larger populations of predators are maintained, resulting in apparent competition. Under some circumstances, apparent competition affects model populations as well, although not as severely as it affects mimics. Our results bear on the intriguing puzzle that in nature warning signals are relatively scarce, yet experiments suggest that such signals can be highly advantageous. The availability of alternative prey and numerical responses by predators can overwhelm advantages observed in experiments to keep warning signals in model-mimic systems relatively scarce. [ABSTRACT FROM AUTHOR]

In recent years, interest in considering multiple facets of diversity has grown among community ecologists. Biological communities are complex systems, and exploring multiple facets can help reveal the main processes that drive diversity patterns. In this paper, we used a metacommunity framework to study the taxonomic, phylogenetic, and functional facets of beta diversity in assemblages of aquatic insects (Ephemeroptera and Trichoptera) with data from mountain streams collected in 2 study systems in the Mata Atlântica (Atlantic Forest) of Brazil: 22 streams from the northern coast of the São Paulo State and 33 streams from the southern coast of São Paulo State. We assessed the following: 1) the relative contributions of turnover and nestedness for different facets of beta diversity and 2) the relationships between environmental and spatial factors on the different facets and components of beta diversity. Beta diversities were high for all facets, and turnover was the main component of the taxonomic (based on incidence and abundance) and phylogenetic facets. In contrast, nestedness was an important component of the functional facet. The roles played by environmental and spatial variables varied erratically between the studied facets, insect orders, and study systems. Environment and space were both poor predictors of the different facets of beta diversity. Our results demonstrated that the difficulty of explaining the taxonomic beta diversity observed in other studies of aquatic insect stream metacommunities also arises for other facets of beta diversity (phylogenetic and functional). The high values of turnover found for most facets suggest that conservation strategies should seek to preserve as many streams as possible within a hydrographic network. [ABSTRACT FROM AUTHOR]

Warning signals are a striking example of natural selection present in almost every ecological community – from Nordic meadows to tropical rainforests, defended prey species and their mimics ward off potential predators before they attack. Yet despite the wide distribution of warning signals, they are relatively scarce as a proportion of the total prey available, and more so in some biomes than others. Classically, warning signals are thought to be governed by positive density‐dependent selection, i.e. they succeed better when they are more common. Therefore, after surmounting this initial barrier to their evolution, it is puzzling that they remain uncommon on the scale of the community. Here, we explore factors likely to determine the prevalence of warning signals in prey assemblages. These factors include the nature of prey defences and any constraints upon them, the behavioural interactions of predators with different prey defences, the numerical responses of predators governed by movement and reproduction, the diversity and abundance of undefended alternative prey and Batesian mimics in the community, and variability in other ecological circumstances. We also discuss the macroevolution of warning signals. Our review finds that we have a basic understanding of how many species in some taxonomic groups have warning signals, but very little information on the interrelationships among population abundances across prey communities, the diversity of signal phenotypes, and prey defences. We also have detailed knowledge of how a few generalist predator species forage in artificial laboratory environments, but we know much less about how predators forage in complex natural communities with variable prey defences. We describe how empirical work to address each of these knowledge gaps can test specific hypotheses for why warning signals exhibit their particular patterns of distribution. This will help us to understand how behavioural interactions shape ecological communities. [ABSTRACT FROM AUTHOR]

The world is changing at a rapid rate, threatening extinction for a large part of the world's biota. One potential response to those altered conditions is to evolve so as to be able to persist in place. Such evolution includes not just traits themselves, but also the phenotypic plasticity of those traits. We used individual‐based simulations to explore the potential of an evolving phenotypic plasticity to increase the probability of persistence in the response to either a step change or continual, directional change in the environment accompanied by within‐generation random environmental fluctuations. Populations could evolve by altering both their nonplastic and plastic genetic components. We found that phenotypic plasticity enhanced survival and adaptation if that plasticity was not costly. If plasticity was costly, for it to be beneficial the phenotypic magnitude of plasticity had to be great enough in the initial generations to overcome those costs. These results were not sensitive to either the magnitude of the within‐generation correlation between the environment of development and the environment of selection or the magnitude of the environmental fluctuations, except for very small phenotypic magnitudes of plasticity. So, phenotypic plasticity has the potential to enhance survival; however, more data are needed on the ubiquity of trait plasticity, the extent of costs of plasticity, and the rate of mutational input of genetic variation for plasticity. [ABSTRACT FROM AUTHOR]

Abstract: Aim: The species–area (SAR) and species–time relationships (STR) are of vital importance in community ecology. Previous studies suggest that a unified, general species–time–area relationship (STAR) may hold, with non‐independent scaling of richness across space and time. Most STAR studies to date have considered species accumulation curves in relatively homogeneous habitats. Here, we test the generality of the STAR in an island system and assess how factors other than area influence species richness, accumulation and turnover through time. Location: Thousand Island Lake, China. Methods: We surveyed bird communities on 36 islands using line transects, and calculated annual species richness of breeding birds from 2007 to 2015. We built island STAR models at island (island STAR; ISTAR) and transect levels (local community–time–area relationship; LCTAR). We employed partial correlations and multiple regressions to examine potential influences of island attributes other than area (i.e. isolation, edge effect and habitat richness) on slopes of STRs. Results: ISTAR and LCTAR models explained 88.8% and 83.1% of total variance, respectively, and both models have a negative space–time interaction. Richness scales comparably in space and time, for both whole‐island and transect‐level analyses. The partial correlation analysis showed that distance to mainland and perimeter‐to‐area ratio are significantly positively correlated with the time scalar (w), and habitat richness and w are negatively correlated. Multiple regression models identify perimeter‐to‐area ratio as particularly influential. Main conclusions: The STAR pattern generalized to an island system where species turnover is high, indicating an interdependency of time and space in determining species richness. Islands have attributes other than area that influence patterns of species accumulation and turnover through time. Ecologists should consider the interdependence of space and time when characterizing species richness patterns. [ABSTRACT FROM AUTHOR]

Recent controversy over whether biodiversity reduces disease risk (dilution effect) has focused on the ecology of Lyme disease, a tick-borne zoonosis. A criticism of the dilution effect is that increasing host species richness might amplify disease risk, assuming that total host abundance, and therefore feeding opportunities for ticks, increase with species richness. In contrast, a dilution effect is expected when poor quality hosts for ticks and pathogens (dilution hosts) divert tick blood meals away from competent hosts. Even if host densities are additive, the relationship between host density and tick encounters can be nonlinear if the number of ticks that encounter a host is a saturating function of host density, which occurs if ticks aggregate on the remaining hosts rather than failing to find a host before death. Both dilution and amplification are theoretical possibilities, and assessing which is more prevalent required detailed analyses of empirical systems. We used field data to explore the degree of tick redistribution onto fewer individuals with variation in intraspecific host density and novel data-driven models for tick dynamics to determine how changes in vertebrate community composition influence the density of nymphs infected with the Lyme bacterium. To be conservative, we allowed total host density to increase additively with species richness. Our long-term field studies found that larval and nymphal ticks redistribute onto fewer individuals as host densities decline, that a large proportion of nymphs and adults find hosts, and that mice and chipmunks feed a large proportion of nymphs. White-footed mice, eastern chipmunks, short-tailed shrews, and masked shrews were important amplification hosts that greatly increased the density of infected nymphs. Gray squirrels and Virginia opossums were important dilution hosts. Removing these two species increased the maximum number of larvae attached to amplification hosts by 57%. Raccoons and birds were minor dilution hosts under some conditions. Even under the assumption of additive community assembly, some species are likely to reduce the density of infected nymphs as diversity increases. If the assumption of additivity is relaxed, then species that reduce the density of small mammals through predation or competition might substantially reduce disease risk. [ABSTRACT FROM AUTHOR]

Research on the ecology of top predators - upper trophic level consumers that are relatively free from predation once they reach adult size - has provided regular contributions to general ecology and is a rapidly expanding and increasingly experimental, multidisciplinary and technological endeavour. Yet, an exponentially expanding literature coupled with rapid disintegration into specialized, disconnected subfields for study (e.g. vertebrate predators versus invertebrate predators, community ecology versus biological control etc.) increasingly means that we are losing a coherent, integrated understating of the role and importance of these species in ecosystems. This process of canalization is likely to hinder sharing of scientific discovery and continued progress, especially as there is a growing need to understand the generality of the top-down forcing, as demonstrated for some members of this group. Here, we propose ways to facilitate synthesis by promoting changes in mentality and awareness among specialists through increased debate and collaboration, conceptual reviews and a series of exemplary case studies. The strategy will rely on the collective contribution by all scientists in the field and will strive to consolidate and formalise top-order predation as a holistic, cohesive, cross-taxonomical field of research studying the ecology, evolution and behaviour of apex predators and their capability to exert top-down forcing on lower trophic levels. [ABSTRACT FROM AUTHOR]

Theoretical models of tree-grass coexistence in savannas have focused primarily on the role of resource availability and fire. It is clear that herbivores heavily impact vegetation structure in many savannas, but their role in driving tree-grass coexistence and the stability of the savanna state has received less attention. Theoretical models of tree-grass dynamics tend to treat herbivory as a constant rather than a dynamic variable, yet herbivores respond dynamically to changes in vegetation structure in addition to modifying it. In particular, many savannas host two distinct herbivore guilds, grazers and browsers, both of which have the potential to exert profound effects on tree/grass balance. For example, grazers may indirectly favor tree recruitment by suppressing the destructive effects of fire, and browsers may facilitate the expansion of grassland by reducing the competitive dominance of trees. We use a simple theoretical model to explore the role of grazer and browser dynamics on savanna vegetation structure and stability across fire and resource availability gradients. Our model suggests that herbivores may expand the range of conditions under which trees and grasses are able to stably coexist, as well as having positive reciprocal effects on their own niche spaces. In addition, we suggest that given reasonable assumptions, indirect mutualisms can arise in savannas between functional groups of herbivores because of the interplay of consumption and ecosystem feedbacks. [ABSTRACT FROM AUTHOR]

Introduced species disrupt native communities and biodiversity worldwide. Parasitic infections (and at times, their absence) are thought to be a key component in the success and impact of biological invasions by plants and animals. They can facilitate or limit invasions, and positively or negatively impact native species., Parasites have not only direct effects on their hosts, but also indirect effects on the species with which their hosts interact. Indirect effects include density-mediated effects (resulting from parasite-induced reduction in host reproduction and survival) as well as trait-mediated indirect effects (resulting from parasite-induced changes in host phenotype, behaviour or life history). These effects are not mutually exclusive but often interact., The importance of these indirect interactions for invasion success, and the extent to which these effects ramify throughout communities and influence ecosystems undergoing biological invasion provide the focus of our review. Examples from the animal and plant literature illustrate the importance of parasites in mediating both competitive and consumer-resource interactions between native and invasive species., Parasites are involved in indirect interactions at all trophic levels. Furthermore, the indirect effects of parasitic infection are important at a range of biological scales from within a host to the whole ecosystem in determining invasion success and impact., To understand the importance of parasitic infection in invasion success and in the outcomes for invaded communities requires an interdisciplinary approach by ecologists and parasitologists, across animal and plant systems. Future research should develop a framework integrating community ecology, evolution and immunology to better understand and manage the spread of invasive species and their diseases. [ABSTRACT FROM AUTHOR]

Current unprecedented declines in biodiversity reduce the ability of ecological communities to provide many fundamental ecosystem services. Here we evaluate evidence that reduced biodiversity affects the transmission of infectious diseases of humans, other animals and plants. In principle, loss of biodiversity could either increase or decrease disease transmission. However, mounting evidence indicates that biodiversity loss frequently increases disease transmission. In contrast, areas of naturally high biodiversity may serve as a source pool for new pathogens. Overall, despite many remaining questions, current evidence indicates that preserving intact ecosystems and their endemic biodiversity should generally reduce the prevalence of infectious diseases. [ABSTRACT FROM AUTHOR]

The diversity of life is ultimately generated by evolution, and much attention has focused on the rapid evolution of ecological traits. Yet, the tendency for many ecological traits to instead remain similar over time [niche conservatism (NC)] has many consequences for the fundamental patterns and processes studied in ecology and conservation biology. Here, we describe the mounting evidence for the importance of NC to major topics in ecology (e.g. species richness, ecosystem function) and conservation (e.g. climate change, invasive species). We also review other areas where it may be important but has generally been overlooked, in both ecology (e.g. food webs, disease ecology, mutualistic interactions) and conservation (e.g. habitat modification). We summarize methods for testing for NC, and suggest that a commonly used and advocated method (involving a test for phylogenetic signal) is potentially problematic, and describe alternative approaches. We suggest that considering NC: (1) focuses attention on the within-species processes that cause traits to be conserved over time, (2) emphasizes connections between questions and research areas that are not obviously related (e.g. invasives, global warming, tropical richness), and (3) suggests new areas for research (e.g. why are some clades largely nocturnal? why do related species share diseases?). [ABSTRACT FROM AUTHOR]

Infectious disease influences the dynamics of host populations and the structure of species communities via impacts on host demography. Species that share infectious diseases are well-known to interact indirectly through the process of apparent competition, but there has been little attention given to the role of vectors in these indirect interactions. Here we explore how vector-borne disease and host-vector interactions can drive apparent competitive interactions. We show that different facets of the ecology associated with vector-host-host interactions affect the structure of the three-species assemblage. Crucially, the patterns associated with invasion of alternative hosts, the spread of the infectious disease by the vector, and the dynamics of the community interactions are influenced by the mode of transmission. We highlight the role of alternative hosts on disease amplification, dilution and magnification and discuss the results with reference to recent developments in apparent competition and community structure. [ABSTRACT FROM AUTHOR]

The integration of community ecology into the understanding and management of vectors and vector-borne diseases has largely occurred only recently. This compendium examines a variety of community interactions that can affect vector or vector-borne disease dynamics. They include: the importance of risk of predation, risk of ectoparasatism, competition, interactions of competition with transgenic control, apparent competition mediated through vectors, indirect effects of pesticides, vector diversity, and parasite diversity within a vector. In this paper, we summarize these studies and introduce several additional important questions in need of further exploration. [ABSTRACT FROM AUTHOR]

The article presents a study on the potential effects of alternative rainfall regimes and antipoaching in the wildebeest (Connochaetes taurinus) migratory population in the Greater Serengeti Ecosystem (GSE) in East Africa. The study used the socioecological model HUMan-EnvironmenT interactions (HUMENTS) to investigate the dynamics of wildebeest and human populations. It says that changes in rainfall and antipoaching have converse effects on socioeconomic and ecological portions of the system.

Multiple hypotheses have been proposed to explain the annual migration of the Serengeti wildebeest, but few studies have compared distribution patterns with environmental drivers.We used a rainfall-driven model of grass dynamics and wildebeest movement to generate simulated monthly wildebeest distributions, with wildebeest movement decisions depending on 14 candidate models of adaptive movement in response to resource availability. We used information-theoretic approaches to compare the fits of simulated and observed monthly distribution patterns at two spatial scales over a 3-year period. Models that included the intake rate and nitrogen (N) concentration of green grass and the suppressive effect of tree cover on grass biomass provided the best model fits at both spatial scales tested, suggesting that digestive constraints and protein requirements may play key roles in driving migratory behavior. The emergence of a migration was predicted to be dependent on the ability of the wildebeest to track changes in resource abundance at relatively large scales (180-100 km). When movement decisions are based solely on local resource availability, the wildebeest fail to migrate across the ecosystem. Our study highlights the potentially key role of strong and countervailing seasonally driven rainfall and fertility gradients—a consistent feature of African savanna ecosystems—as drivers of long-distance seasonal migrations in ungulates. [ABSTRACT FROM AUTHOR]

The article discusses the effect of changes in herbivore population density on the tree cover in savanna ecosystems in Serengeti, east Africa. A spatially realistic simulation model of vegetation, fire, and dominant herbivore dynamics was developed to project the ecosystem 100 years into the future from its present state under different fire. It shows that grazers can modulate the effect of fire and the strength of the interaction between fire and browsers by altering fuel loads and responding to the distribution of grass across the landscape.

Ecological coupling by material exchanges or dispersal between spatially distinct communities has important impacts on ecological processes, such as diversity–stability relationships, ecosystem function, and food web dynamics. One important mode of coupling between ecosystems occurs via organisms with complex life histories, which often switch between distinct ecosystems during their life cycle, and so can be channels of material exchanges between these ecosystems. Some organisms with complex life histories (e.g. frogs, dragonflies) can be abundant and effective predators during one or more life stages, and so provide conduits for strong direct and indirect interactions across ecosystem boundaries, linking the dynamics of discrete and often quite dissimilar community types. We present simple models and a case study (tailored to pond ecosystems), to explore how interactions within larval habitats can indirectly impact ecological interactions in adult habitats. Using our case study as a springboard, we propose that cohorts of predators emerging from natal habitats (e.g. ponds) cast ‘predation shadows’ on the surrounding adult (e.g. terrestrial) landscape. Trophic interactions within ponds, and the distribution of ponds on the landscape, can thus affect the spatial pattern in the strength of these predation shadows, creating strong spatial patterning in terrestrial trophic cascades. Our findings emphasize the importance of organisms with complex life histories as generators of strong links across ecosystem boundaries, and as potential sources of spatial variation in the strength and indirect impacts of interspecific interactions. [ABSTRACT FROM AUTHOR]

The article discusses the role of seasonality in habitat selection. According to biologist Steve Fretwell, most populations live in a seasonal environment. He theorizes that the exact temporal pattern of variation in demographic parameters affects the extent at which seasonal cycles affect a population size. Experimental and theoretical studies on the role of seasonality in population dynamics are cited. Also explained are the implications of seasonality to evolutionary process and population mobility.

Niche conservatism is the phenomenon in which species or other phylogenetic lineages seem to exhibit much the same ecological niche over their geographical ranges or over evolutionary time scales. Previous studies have suggested that optimal habitat selection call constrain niche evolution (and thus may help explain niche conservatism), in effect by preventing populations from experiencing unfavorable sink environments with conditions outside the niche. This paper relaxes a key assumption in prior literature, by allowing habitat selection decisions to be conditional upon an individual's phenotype. We use individual-based simulations of evolution in source-sink landscapes to examine the consequences of phenotype-matching habitat selection. If each individual obeys a "perfect'" habitat selection rule moving to another habitat only if that movement increases the match between its phenotype and the habitat's optimum--then habitat selection can speed up the rate of adaptation to sink environments, and thus facilitate niche evolution. We also note that habitat selection can also indirectly influence the pool of variation available for selection, and thereby potentially alter to some degree this conclusion. [ABSTRACT FROM AUTHOR]

Over the last several decades, there has been a growing appreciation of the importance of nonequilibrial phenomena and transient dynamics in explaining the structure of ecological communities. This paper provides an overview of theoretical themes related to resource pulses. Theoretical models suggest short-term responses to a single pulse can qualitatively differ from longer-term responses. Recurrent resource pulses can alter community structure, permitting coexistence that otherwise would not occur, or hamper coexistence mechanisms effective in stable environments. For a given resource input, system responses can be more dramatic with short pulses. Resource pulses can cause transitions between alternative states. Dispersal permits species to exploit locally sporadic-resource pulses and persist in environments that on average are unsuitable. All these issues are ripe for further theoretical explorations. [ABSTRACT FROM AUTHOR]

Understanding the process of adaptation to novel environments may help to elucidate several ecological phenomena, from the stability of species range margins to host-pathogen specificity and persistence in degraded habitats. We study evolution in one type of novel environment: a sink habitat where populations cannot persist without recurrent immigration from a source population. Previous studies on source-sink evolution have focused on how extrinsic environmental factors influence adaptation to a sink, but few studies have examined how intrinsic genetic factors influence adaptation. We use an individual-based model to explore how genetic canalization that evolves in gene regulation networks influences the adaptation of a population to a sink. We find that as canalization in the regulation network increases, the probability of adaptation to the novel habitat decreases. When adaptation to the habitat does occur, it is usually preceded by a breakdown of canalization. As evolution continues in the novel habitat, canalization reemerges, but a legacy of the breakdown may remain, even after several generations. We also find that environmental noise tends to increase the probability of adaptation to the novel habitat. Our results suggest that the details of genetic architecture can significantly influence the likelihood of niche evolution in novel environments. [ABSTRACT FROM AUTHOR]

Predation can be intense, creating strong direct and indirect effects throughout food webs. In addition, ecologists increasingly recognize that fluxes of organisms across ecosystem boundaries can have major consequences for community dynamics. Species with complex life histories often shift habitats during their life cycles and provide potent conduits coupling ecosystems. Thus, local interactions that affect predator abundance in one ecosystem (for example a larval habitat) may have reverberating effects in another (for example an adult habitat). Here we show that fish indirectly facilitate terrestrial plant reproduction through cascading trophic interactions across ecosystem boundaries. Fish reduce larval dragonfly abundances in ponds, leading to fewer adult dragonflies nearby. Adult dragonflies consume insect pollinators and alter their foraging behaviour. As a result, plants near ponds with fish receive more pollinator visits and are less pollen limited than plants near fish-free ponds. Our results confirm that strong species interactions can reverberate across ecosystems, and emphasize the importance of landscape-level processes in driving local species interactions. [ABSTRACT FROM AUTHOR]

Species-area relationships have been observed for virtually all major groups of macroorganisms that have been studied to date but have not been explored for microscopic phytoplankton algae, which are the dominant producers in many freshwater and marine ecosystems. Our analyses of data from 142 different natural ponds, lakes, and oceans and 239 experimental ecosystems reveal a strong species-area relationship with an exponent that is invariant across ecosystems that span >15 orders of magnitude in spatial extent. A striking result is that the species-area relationship derived from small-scale experimental studies correctly scales up to natural aquatic ecosystems. These results significantly broaden our knowledge of the effects of island size on biodiversity and also confirm the relevance of experimentally derived data to the analysis and understanding of larger-scale ecological patterns. In addition, they confirm that patterns in microbial diversity are strongly consistent with those that have been repeatedly reported in the literature for macroorganisms. [ABSTRACT FROM AUTHOR]

We examine the impact of temporal variation on adaptive evolution in ‘sink’ environments, where a species encounters conditions outside its niche. Sink populations persist because of recurrent immigration from sources. Prior studies have highlighted the importance of demographic constraints oil adaptive evolution in sinks and revealed that adaptation is less likely in harsher sinks. We examine two complementary models of population and evolutionary dynamics in sinks: a continuous state quantitative genetics model and an individual based model. In the former, genetic variance is fixed; in the latter, genetic variance varies because of mutation, drift, and sampling. In both models, a population in a constant harsh sink environment can exist in alternative states: local maladaptation (phenotype comparable to immigrants from the source) or adaptation (phenotype near the local optimum). Temporal variation permits transitions between these states. We show that moderate amounts of temporal variation can facilitate adaptive evolution in sinks, permitting niche evolution, particularly for slow or autocorrelated variation. Such patterns of temporal variation may particularly pertain to sinks caused by biotic interactions (e.g., predation). Our results are relevant to the evolutionary dynamics of species' ranges, the fate of exotic invasive species, and the evolutionary emergence of infectious diseases into novel hosts. [ABSTRACT FROM AUTHOR]

In the absence of other limiting factors, assemblages in which species share a common, effective natural enemy are not expected to persist. Although a variety of mechanisms have been postulated to explain the coexistence of species that share natural enemies, the role of productivity gradients has not been explored in detail. Here, we examine how enrichment can affect the outcome of apparent competition. We develop a structured resource/consumer/ natural enemy model in which the prey are exposed to attacks during a vulnerable life phase, the length of which depends on resource availability. With a single prey species, the model exhibits the "paradox of enrichment," with unstable dynamics at high levels of re-source productivity. We extend this model to consider two prey species linked by a shared predator, each with their own distinct resource base. We derive invasion and stability conditions and examine how enrichment influences prey species exclusion and coexistence. Contrary to expectations from simpler, prey-dependent models, apparent competition is not necessarily strong at high productivity, and prey species coexistence may thus be more likely in enriched environments. Further, the coexistence of apparent competitors may be facilitated by unstable dynamics. These results contrast with the standard theory that apparent competition in productive environments leads to nonpersistent interactions and that coexistence of multi-species interactions is more likely under equilibrial conditions. [ABSTRACT FROM AUTHOR]

Abstract This contribution proposes the meta-ecosystem concept as a natural extension of the metapopulation and metacommunity concepts. A meta-ecosystem is defined as a set of ecosystems connected by spatial flows of energy, materials and organisms across ecosystem boundaries. This concept provides a powerful theoretical tool to understand the emergent properties that arise from spatial coupling of local ecosystems, such as global source–sink constraints, diversity–productivity patterns, stabilization of ecosystem processes and indirect interactions at landscape or regional scales. The meta-ecosystem perspective thereby has the potential to integrate the perspectives of community and landscape ecology, to provide novel fundamental insights into the dynamics and functioning of ecosystems from local to global scales, and to increase our ability to predict the consequences of land-use changes on biodiversity and the provision of ecosystem services to human societies. [ABSTRACT FROM AUTHOR]

The natural world is variable both in space and in time, but little ecological theory has been explicitly devoted to analyzing the consequences of both kinds of variability operating simultaneously. This issue is examined relative to the indirect interaction of apparent competition, which can limit the membership of prey communities. One limiting case that provides a useful starting point is to imagine that a local community is influenced by coupling with an external source landscape, but has little reciprocal influence on that landscape. There usually will be some rate of input of a locally inferior species that suffices to ‘swamp’ a superior species and drive it to extinction. We use simple models of apparent competition to show that when one superimposes upon this scenario temporal fluctuations, mediated through shifts in parameter values, such variation can either magnify the importance of the external input, or reduce it, depending on which component of the system experiences variation. We examine this in the case of both slow variation (for which we suggest a protocol that may be useful in a wide range of ecological models), and fast variation. The theoretical studies presented here provide examples of the rich range of outcomes that may arise due to temporal variability in spatially heterogeneous landscapes. [ABSTRACT FROM AUTHOR]

Ecologists increasingly recognize that a consideration of spatial dynamics is essential for resolving many classical problems in community ecology. In the present paper, I argue that understanding how trophic interactions influence population stability can have important implications for the expression of spatial processes. I use two examples to illustrate this point. The first example has to do with spatial determinants of food chain length. Prior theoretical and empirical work has suggested that colonization–extinction dynamics can influence food chain length, at least for specialist consumers. I briefly review evidence and prior theory that food chain length is sensitive to area. A metacommunity scenario, in which each of various patches can have a food chain varying in length (but in which a consumer is not present on a patch unless its required resource is also present), shows that alternative landscape states are possible. This possibility arises if top predators moderate unstable interactions between intermediate predators and basal resources. The second example has to do with the impact of recurrent immigration on the stability of persistent populations. Immigration can either stabilize or destabilize local population dynamics. Moreover, an increase in immigration can decrease average population size for unstable populations with direct density-dependence, or in predator–prey systems with saturating functional responses. These theoretical models suggest that the interplay of temporal variation and spatial fluxes can lead to novel qualitative phenomena. [ABSTRACT FROM AUTHOR]

Interspecific interactions reflect the cumulative consequences of individual behavioral acts. The foraging decisions made by predators influence the way in which predation shapes the structure of prey communities. Alternative prey species co-occurring in a patch embedded in a matrix of many similar patches may interact through a shared mobile predator in two distinct ways. First, the functional response by an individual predator foraging in the patch to one prey species may be affected by the density of a second prey species in the patch (e.g., any time spent handling one prey reduces the time available for capturing other prey). Second, the presence of a second prey species may alter the propensity of predators to aggregate or remain in a given patch. We argue that this aggregative numerical response can in many circumstances generate -, - interactions (apparent competition) between prey species that otherwise would not interact. This is most likely if predators use a simple optimality criterion for prey selectivity within patches and the marginal-value theorem for deciding when to enter and leave patches. By contrast, if predators have suboptimal diets within patches but leave in accord with the marginal-value theorem, alternative prey may experience a +, - interaction; and, if predators use patches independently of prey availability, a +, + interaction between alternative prey can occur. Hence, the qualitative character of the interaction between alternative prey in a patchy environment depends on the degree to which predators do, or do not, match the canonical predictions of optimal foraging theory. [ABSTRACT FROM AUTHOR]

Yogi Berra is often credited * with having opined that ‘prediction is very difficult, especially about the future’. There is no discipline for which this statement holds with more force than invasion biology, where it has been historically very challenging to predict the fate of introduced species ( Williamson 2006 ). Some species after introduction quickly go extinct. Other relatively similar species may persist, but with little spread from their initial beachheads. Yet others can become aggressive invaders, with devastating consequences for native communities and ecosystems. This lack of predictability may of course sometimes reflect a simple lack of knowledge, both about key features of a species’ basic biology, and about the environmental and community milieu in which invasion occurs ( Williamson 2006 ). However, unpredictability may also arise from a fundamental fact about populations of living organisms – they almost always contain genetic variation, and so are not fixed entities responding to an environmental template, but instead labile in how they cope with the environment, over many spatial and temporal scales. Chance vicissitudes in the origination, maintenance and spatial organization of genetic variation could play a large role in generating the observed unpredictability in the fates of introduced species. The degree to which a particular introduced species becomes ‘invasive’– to the extent of coming to the attention of worried land managers, governmental officials and the public – may reflect in part its capacity for adaptive evolution across a wide range of environmental conditions. [ABSTRACT FROM AUTHOR]

The article focuses on the problem of understanding the stability of complex food webs. It was emphasized that ecological communities are among the most complex entities studied by scientists, as they are composed of thousands of species with many distinct lifestyles, interacting in a myriad of ways.

There is no consensus on when biotic interactions impact the range limits of species. Starting from MacArthur’s use of invasibility to understand how biotic interactions influence coexistence, here we examine how biotic interactions shape species distributions. Range limits emerge from how birth, death, and movement rates vary with the environment. We clarify some basic issues revolving around niche definitions, illustrated with simple resource–consumer theory. We then highlight two different avenues for linking community theory and range theory; the first based on calculating the effects of biotic interactions on range limits across scales and landscape configurations, and the second based on aggregate measures of diffuse interactions and network strength. We conclude with suggestions for a future research agenda. [ABSTRACT FROM AUTHOR]

Much of the focus in evolutionary biology has been on the adaptive differentiation among organisms. It is equally important to understand the processes that result in similarities of structure among systems. Here, we discuss examples of similarities occurring at different ecological scales, from predator–prey relations (attack rates and handling times) through communities (food-web structures) to ecosystem properties. Selection among systemic configurations or patterns that differ in their intrinsic stability should lead generally to increased representation of relatively stable structures. Such nonadaptive, but selective processes that shape ecological communities offer an enticing mechanism for generating widely observed similarities, and have sparked new interest in stability properties. This nonadaptive systemic selection operates not in opposition to, but in parallel with, adaptive evolution. [ABSTRACT FROM AUTHOR]

Predator-prey interactions are ubiquitous and powerful forces that structure ecological communities. 1–3 Habitat complexity has been shown to be particularly important in regulating the strength of predator-prey interactions. 4–6 While it is well established that changes in habitat structure can alter the efficacy of predatory and anti-predatory behaviors, 7–9 little is known about the consequences of engineering activity by prey species who modify the external environment to reduce their own predation risk. Using field surveys and manipulative experiments, we evaluated how habitat modification by Brandt's voles (Lasiopodomys brandtii) influences predation risk from a principal avian predator (shrike; Lanius spp.) in a steppe grassland, located in Inner Mongolia, China. We found that voles actively modify habitat structure by cutting down a large, unpalatable bunchgrass species (Achnatherum splendens) in the presence of shrikes, a behavior that disappeared when these avian predators were excluded experimentally. The damage activities of these voless dramatically decreased the volume of unpalatable grasses, which in turn reduced visitations by shrikes and thus mortality rates. Our study shows that herbivorous prey that act as ecosystem engineers can directly reduce their own predation risk by modifying habitat structure. Given the ubiquity of predation risks faced by consumers, and the likely ability of many consumers to alter the habitat structure in which they live, the interplay between predation risk and ecosystem engineering may be an important but unappreciated mechanism at play in natural communities. [Display omitted] • Voles modified habitat structure by destroying a large, unpalatable bunchgrass • Damage activities of voles decreased the plant volume of the bunchgrasses • Vole damage activities were enhanced at the presence of the predatory birds • Habitat modifications by voles reduced predation risk and increased vole survival Zhong et al. show that by damaging a large, unpalatable bunch grass, Brandt's voles in steppe grasslands in China can reduce the predation risk from avian predators (Lanius spp.) probably due to improved vision. Habitat modifications by voles can reduce the visiting frequency of avian predators and thus increase the survival of voles. [ABSTRACT FROM AUTHOR]

Until recently, large apex consumers were ubiquitous across the globe and had been for millions of years. The loss of these animals may be humankind's most pervasive influence on nature. Although such losses are widely viewed as an ethical and aesthetic problem, recent research reveals extensive cascading effects of their disappearance in marine, terrestrial, and freshwater ecosystems worldwide. This empirical work supports tong-standing theory about the role of top-down forcing in ecosystems but also highlights the unanticipated impacts of trophic cascades on processes as diverse as the dynamics of disease, wildfire, carbon sequestration, invasive species, and biogeochemical cycles. These findings emphasize the urgent need for interdisciplinary research to forecast the effects of trophic downgrading on process, function, and resilience in global ecosystems. [ABSTRACT FROM AUTHOR]

Predicting the impacts of climate change on species is one of the biggest challenges that ecologists face. Predictions routinely focus on the direct effects of climate change on individual species, yet interactions between species can strongly influence how climate change affects organisms at every scale by altering their individual fitness, geographic ranges and the structure and dynamics of their community. Failure to incorporate these interactions limits the ability to predict responses of species to climate change. We propose a framework based on ideas from global-change biology, community ecology, and invasion biology that uses community modules to assess how species interactions shape responses to climate change. [Copyright &y& Elsevier]

Many models of local species interactions predict the occurrence of priority effects due to alternative stable equilibria (ASE). However, few empirical examples of ASE have been shown. One possible explanation for the disparity is that local ASE are difficult to maintain regionally in patch dynamic models. Here we examine two possible mechanisms for regional coexistence of species engaged in local ASE. Biotically generated heterogeneity (e.g., habitat modification that favors further invasion by conspecifics) results in regional exclusion of one species at equilibrium. In contrast, abiotic heterogeneity due to spatial variation in resource supply ratios generates local-scale ASE and ensures regional coexistence with sufficiently broad environmental gradients. Abiotic heterogeneity can result in a species that is the dominant competitor over some of its range being excluded if the area where it is dominant is too small. Biotic heterogeneity can lead to alternative stable landscapes or regional priority effects, while abiotic heterogeneity results in regional determinism. Broad environmental gradients in resource supply favor regional coexistence of species that exhibit local ASE. [Copyright &y& Elsevier]