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Dispersal among local communities is fundamental to the metacommunity concept but is only important to the metacommunity structure if dispersal causes distortions of species abundances away from what local ecological conditions favour. We know from much previous work that dispersal can cause such abundance distortions. However, almost all previous theoretical studies have only considered one species alone or two interacting species (e.g. competitors or predator and prey). Moreover, a systematic analysis is needed of whether different dispersal strategies (e.g. passive dispersal versus demographic habitat selection) result in different abundance distortion patterns, how these distortion patterns change with local food web structure, and how the dispersal propensities of the interacting species might evolve in response to one another. In this article, we show using computer simulations and analytical models that abundance distortions occur in simple food webs with both passive dispersal and habitat selection, but habitat selection causes larger distortions. Additionally, patterns in the evolution of dispersal propensity in interacting species are very different for these two dispersal strategies. This study identifies that the dispersal strategies employed by interacting species critically shape how dispersal will influence metacommunity structure. This article is part of the theme issue 'Diversity-dependence of dispersal: interspecific interactions determine spatial dynamics'. [ABSTRACT FROM AUTHOR]

The importance of dispersal rates and distances has long been appreciated by ecologists and evolutionary biologists. An emerging field of research is revealing how temporal variation in dispersal can substantially influence ecological and evolutionary outcomes. We review how dispersal rates can temporally vary substantially in many ecosystems, a pattern that is particularly well‐documented for aquatic organisms but is likely pervasive in terrestrial ecosystems as well. We then synthesize the effects of temporal variation in dispersal on five key ecological and evolutionary processes: 1) metapopulation dynamics, 2) local adaptation, 3) range limits and range expansions, 4) species coexistence and 5) metacommunity dynamics. Our review demonstrates that temporal variation in dispersal is more than just statistical 'noise' but can in fact lead to different outcomes than expected were dispersal temporally constant. For example, increasing the magnitude of temporal variation in dispersal can lead to lower metapopulation growth rates, permit greater local adaptation, facilitate and accelerate range expansion, increase regional coexistence, and alter local and regional species diversity. These effects of temporal variation in dispersal can inform conservation and natural resource management decisions such as prioritization in spatial planning, management of spillover from domesticated or captive populations into native populations, and the design of effective control strategies for invasive species. [ABSTRACT FROM AUTHOR]

Humans greatly influence the ecosystems they live in and the lives of a wide range of taxa they share space with. Specifically, human hunting and harvesting has resulted in many species acclimating via diverse behavioral responses, often quite rapidly. This review provides insights into how hunting and harvesting can elicit behavioral changes. These responses emerge from a species' previous and evolving ability to assess risk imposed by hunters and respond accordingly; a predator–prey game thus ensues, where both players may change tactics over time. If hunting is persistent, and does not result in the taxa's extirpation, species are expected to develop adaptations to cope with hunting via natural selection by undergoing shifts in morphology and behavior. This review summarizes the various ways that human hunting intentionally and incidentally alters such evolutionary changes. These changes in turn can influence other species interactions and whole ecosystems. Additionally, alterations in behaviors can provide useful indicators for conservation and evolutionarily enlightened management strategies, and humans should use them to gain insights into our own socio-economic circumstances. [ABSTRACT FROM AUTHOR]

Reproductive mode may strongly impact adaptation in spatially varying populations linked by dispersal, especially when sexual and clonal offspring differ in dispersal. We determined how spatial structure affects adaptation in populations with mixed clonal and sexual reproduction. In a source-sink quantitative genetic deterministic model (with stabilizing selection around different optima), greater clonal reproduction or parent-offspring association (a measure of the part of the parent's phenotype other than the additive genetic component inherited by clonal offspring) increased the selective difference (difference between phenotypic optima) allowing sink populations to adapt. Given dispersal differences between clonally and sexually produced juveniles, adaptation increased with an increasing fraction of clonal dispersers. When considering migrational meltdown, partially clonal reproduction reduced cases where dispersal caused habitat loss. Stochastic individual-based simulations support these results, although the effect of differential dispersal was reversed, with decreased clonal dispersal allowing greater adaptation. These results parallel earlier findings that for an instantaneous shift in phenotypic optimum, increasing clonality allowed population persistence for a greater shift; here, selective change is spatial rather than temporal. These results may help explain the success of many partially clonal organisms in invading new habitats, complementing traditional explanations based on avoiding Allee effects. [ABSTRACT FROM AUTHOR]

Food has long been known to perform dual functions of nutrition and medicine, but mounting evidence suggests that complex host‐pathogen dynamics can emerge along continuous resource gradients. Empirical examples of nonmonotonic responses of infection with increasing host resources (e.g., low prevalence at low and high resource supply but high prevalence at intermediate resources) have been documented across the tree of life, but these dynamics, when observed, often are interpreted as nonintuitive, idiosyncratic features of pathogen and host biology. Here, by developing generalized versions of existing models of resource dependence for within‐ and among‐host infection dynamics, we provide a synthetic view of nonmonotonic infection dynamics. We demonstrate that where resources jointly impact two (or more) processes (e.g., growth, defense, transmission, mortality, predation), nonmonotonic infection dynamics, including alternative states, can emerge across a continuous resource supply gradient. We review the few empirical examples that concurrently measured resource effects on multiple rates and pair this with a wide range of examples in which resource dependence of multiple rates could generate nonmonotonic infection outcomes under realistic conditions. This review and generalized framework highlight the likely generality of such resource effects in natural systems and point to opportunities ripe for future empirical and theoretical work. [ABSTRACT FROM AUTHOR]

Habitat loss is often considered the greatest near‐term threat to biodiversity, while the impact of habitat fragmentation remains intensely debated. A key issue of this debate centers on the problem of scale–landscape or patch–at which to assess the consequences of fragmentation. Yet patterns are often confounded across scales, and experimental designs that could solve this scaling problem remain scarce. We conducted two field experiments in 30 experimental landscapes in which we manipulated habitat loss, fragmentation, and patch size for a community of four insect herbivores that specialize on the cactus Opuntia. In the first experiment, we destroyed 2088 Opuntia patches in either aggregated or random patterns and compared the relative effects of landscape‐scale loss and fragmentation to those of local patch size on species occurrence. This experiment focused on manipulating the relative separation of remaining patches, where we hypothesized that aggregated loss would disrupt dispersal more than random loss, leading to lower occurrence. In the second experiment, we destroyed 759 Opuntia patches to generate landscapes that varied in patch number and size for a given amount of habitat loss and assessed species occurrence. This experiment focused on manipulating the subdivision of remaining habitat, where we hypothesized that an increase in the number of patches for a given amount of loss would lead to negative effects on occurrence. For both, we expected that occurrence would increase with patch size. We find strong evidence for landscape‐scale effects of habitat fragmentation, with aggregated loss and a larger number of patches for a given amount of habitat loss leading to a lower frequency of patches occupied in landscapes. In both experiments, occurrence increased with patch size, yet interactions of patch size and landscape‐scale loss and fragmentation drove species occurrence in patches. Importantly, the direction of effects were consistent across scales and effects of patch size were sufficient to predict the effects of habitat loss and fragmentation across entire landscapes. Our experimental results suggest that changes at both the patch and landscape scales can impact populations, but that a long‐standing pattern—the patch‐size effect—captures much of the key variation shaping patterns of species occurrence. [ABSTRACT FROM AUTHOR]

Community structure depends jointly on species' responses to, and effects on, environmental factors. Many such factors, including detritus, are studied in ecosystem ecology. Detritus in terrestrial ecosystems is dominated by plant litter (nonliving organic material), which, in addition to its role in material cycling, can act as a niche factor modulating interactions among plants. Litter thus links traditional community and ecosystem processes, which are often studied separately. We explore this connection using population dynamics models of two plant species and a litter pool. We first find conditions determining the outcome of interactions between these species, highlighting the role that litter plays and the role of broader ecosystem parameters, such as decomposition rate. Species trade-offs in tolerance to direct competition and litter-based interference competition allow for coexistence, provided the litter-tolerant species produces more litter at the population level; otherwise, priority effects may result. When species coexist, litter-mediated interactions between plants disrupt the traditional relationship between biomass accumulation and decomposition. Increasing decomposition rate may have no effect on standing litter density and, in some cases, may even increase litter load. These results illustrate how ecosystem variables can influence community outcomes that then feed back to influence the ecosystem. [ABSTRACT FROM AUTHOR]

All individuals transition through various life stages over the course of their development and nearly all organisms must contend with infectious disease at some point in their lives. Yet the intersection of these two universal features of life—stage structure and infectious disease—and their joint effects on population dynamics are poorly understood. Here, we develop a two-stage population model in which density dependence acts on juvenile maturation, and infectious disease affects either juveniles or adults via reduction in maturation, reproduction, or survival. In the absence of disease, this form of density dependence can generate persistent population oscillations. We examine whether infectious disease further accentuates these oscillations (by augmenting their amplitude) or stabilizes them (by reducing their amplitude). We find that, for moderate transmission rates (a proxy for disease incidence), disease can stabilize dynamics. In contrast, fast disease transmission is not generally stabilizing, which is, at least in part, due to disease overexploitation of the infectious class. Hydra effects are possible in the model due to density overcompensation and occur when disease increases juvenile mortality or decreases adult fecundity (but do not occur when disease augments adult mortality or reduces maturation). Slow maturation, large disease-free population size, and strong density-dependent population regulation can each lower the transmission rate required for the infectious disease to invade the population. [ABSTRACT FROM AUTHOR]

Genetic connectivity lies at the heart of evolutionary theory, and landscape genetics has rapidly advanced to understand how gene flow can be impacted by the environment. Isolation by landscape resistance, often inferred through the use of circuit theory, is increasingly identified as being critical for predicting genetic connectivity across complex landscapes. Yet landscape impediments to migration can arise from fundamentally different processes, such as landscape gradients causing directional migration and mortality during migration, which can be challenging to address. Spatial absorbing Markov chains (SAMC) have been introduced to understand and predict these (and other) processes affecting connectivity in ecological settings, but the relationship of this framework to landscape genetics remains unclear.Here, we relate the SAMC to population genetics theory, provide simulations to interpret the extent to which the SAMC can predict genetic metrics and demonstrate how the SAMC can be applied to genomic data using an example with an endangered species, the Panama City crayfish Procambarus econfinae, where directional migration is hypothesized to occur.The use of the SAMC for landscape genetics can be justified based on similar grounds to using circuit theory, as we show how circuit theory is a special case of this framework. The SAMC can extend circuit‐theoretic connectivity modelling by quantifying both directional resistance to migration and acknowledging the difference between migration mortality and resistance to migration. Our empirical example highlights that the SAMC better predicts population structure than circuit theory and least‐cost analysis by acknowledging asymmetric environmental gradients (i.e. slope) and migration mortality in this species.These results provide a foundation for applying the SAMC to landscape genetics. This framework extends isolation‐by‐resistance modelling to account for some common processes that can impact gene flow, which can improve predicting genetic connectivity across complex landscapes. [ABSTRACT FROM AUTHOR]

Environmental fluctuations are pervasive in nature, but the influence of nondirectional temporal variation on range limits has received scant attention. We synthesize insights from the literature and use simple models to make conceptual points about the potentially wide range of ecological and evolutionary effects of temporal variation on range limits. Because organisms respond nonlinearly to environmental conditions, temporal variation can directionally alter long-term growth rates, either to shrink or to expand ranges. We illustrate this diversity of outcomes with a model of competition along a mortality gradient. Temporal variation can permit transitions between alternative states, potentially facilitating range expansion. We show this for variation in dispersal, using simple source-sink population models (with strong Allee effects, or with gene flow hampering local adaptation). Temporal variation enhances extinction risk owing to demographic stochasticity, rare events, and loss of genetic variation, all tending to shrink ranges. However, specific adaptations to exploit variation (including dispersal) may permit larger ranges than in similar but constant environments. Grappling with temporal variation is essential both to understand eco-evolutionary dynamics at range limits and to guide conservation and management strategies. This article is part of the theme issue 'Species' ranges in the face of changing environments (Part II)'. [ABSTRACT FROM AUTHOR]

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]

Adaptive habitat construction is a process by which individuals alter their environment so as to increase their (inclusive) fitness. Such alterations are a subset of the myriad ways that individuals condition their environment. We present an individual‐based model of habitat construction to explore what factors might favor selection when the benefits of environmental alterations are shared by individuals of the same species. Our results confirm the predictions of inclusive fitness and group selection theory and expectations based on previous models that construction will be more favored when its benefits are more likely to be directed to self or near kin. We found that temporal variation had no effect on the evolution of construction. For spatial heterogeneity, construction was disfavored when the spatial pattern of movement did not match the spatial pattern of environmental heterogeneity, especially when there was spatial heterogeneity in the optimal amount of construction. Under those conditions, very strong selection was necessary to favor genetic differentiation of construction propensity among demes. We put forth a constitutive theory for the evolution of adaptive habitat construction that unifies our model with previous verbal and quantitative models into a formal conceptual framework. [ABSTRACT FROM AUTHOR]

Trait adaptation to a heterogeneous environment can occur through six modes: genetic differentiation of those traits, a jack‐of‐all‐trades phenotypic uniformity, diversified bet‐hedging, phenotypic plasticity, habitat choice, and habitat construction. A key question is what circumstances favor one mode over another, and how they might interact if a system can express more than one mode at a time. We examined the joint evolution of habitat choice and habitat construction using individual‐based simulations. We manipulated when during the life cycle construction occurred and the fitness value of construction. We found that for our model habitat construction was nearly always favored over habitat choice, especially if construction happened after dispersal. Because of the ways that the various modes of adaptation interact with each other, there is no simple answer as to which will be favored; it depends on details of the biology and ecology of a given system. [ABSTRACT FROM AUTHOR]

Plant litter can alter ecosystems and promote plant invasions by altering resource availability, depositing phytotoxins, and transmitting microorganisms to living plants. Transmission of microorganisms from invasive plant litter to live plants may gain importance as invasive plants, which often escape pathogens upon introduction to a new range, acquire new pathogens over time. It is unclear, however, if invasive plant litter affects native plant communities by promoting disease. Microstegium vimineum is an invasive grass that suppresses native populations, in part through litter production, and has acquired new fungal leaf spot diseases since its introduction to the United States. In a greenhouse experiment, we evaluated how M. vimineum litter and its pathogens mediated competition with the native grass Elymus virginicus. M. vimineum litter promoted disease on E. virginicus and suppressed establishment and biomass of both species. Litter had stronger negative effects on E. virginicus than M. vimineum, increasing the relative biomass of M. vimineum. Live plant competition reduced biomass of both species and live M. vimineum increased disease incidence on E. virginicus. Altogether, invasive grass litter suppressed both species, ultimately favoring the invasive species in competition, and increased disease incidence on the native species. [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]

Metapopulation capacity provides an analytic tool to quantify the impact of landscape configuration on metapopulation persistence, which has proven powerful in biological conservation. Yet surprisingly few efforts have been made to apply this approach to multispecies systems. Here, we extend metapopulation capacity theory to predict the persistence of trophically interacting species. Our results demonstrate that metapopulation capacity could be used to predict the persistence of trophic systems such as prey-predator pairs and food chains in fragmented landscapes. In particular, we derive explicit predictions for food chain length as a function of metapopulation capacity, top-down control, and population dynamical parameters. Under certain assumptions, we show that the fraction of empty patches for the basal species provides a useful indicator to predict the length of food chains that a fragmented landscape can support and confirm this prediction for a host-parasitoid interaction. We further show that the impact of habitat changes on biodiversity can be predicted from changes in metapopulation capacity or approximately by changes in the fraction of empty patches. Our study provides an important step toward a spatially explicit theory of trophic metacommunities and a useful tool for predicting their responses to habitat changes. [ABSTRACT FROM AUTHOR]

Emigration propensity (i.e., the tendency to leave undisturbed patches) is a key life‐history trait of organisms in metapopulations with local extinctions and colonizations. Metapopulation models of dispersal evolution typically assume that patch disturbance kills all individuals within the patch, thus causing local extinction. However, individuals may instead be able to leave a patch when it is disturbed, either by fleeing before being killed or simply because the disturbance destroys the patch without causing mortality. This scenario may pertain to a wide range of organisms from horizontally transmitted symbionts, to aquatic insects inhabiting temporary ponds, to vertebrates living in fragmented forests. We generalized a Levins‐type metapopulation model of dispersal evolution by adding a new parameter of disturbance escape probability, which incorporates a second source of dispersal into the model: disturbance‐induced emigration. We show that disturbance escape expands the domain of metapopulation viability and selects for lower rates of emigration propensity when disturbance rates are high. The fitness gains from disturbance‐induced emigration are generally moderate, suggesting that disturbance escape might act more as a complementary dispersal strategy rather than a replacement to emigration propensity, at least for metapopulations that meet the assumptions of the Levins‐type model. Yet disturbance‐induced emigration may in some circumstances rescue a metapopulation from long‐term extinction when the combination of high disturbance rates and low local population growth rates compromises its viability. Further, a metapopulation could persist exclusively by disturbance escape if local carrying capacities are large enough to counterbalance two sources of mortality: mortality driven by disturbance and mortality during dispersal. This study opens two promising research lines: (1) the investigation of disturbance escape in metapopulations of ephemeral habitats with unsaturated populations and non‐equilibrium dynamics and (2) the incorporation of information costs to investigate the joint evolution of disturbance escape and emigration propensity. [ABSTRACT FROM AUTHOR]

Aim: The positive relationship between species richness and area—the species–area relationship (SAR)—is a key principle in ecology. Previous studies show large variation in the SAR across taxa collectively indicating the necessity of a taxon‐focused approach to accurately evaluate biodiversity scaling patterns. Ants are ideal for this given their global distribution and role in ecosystem functioning. Using data from insular ant communities, this study quantified and investigated various attributes of ant SARs and reviewed the SAR literature for ant faunas, world‐wide, to identify specific areas for improvement. Location: Islands around the world. Taxon: Ants (Hymenoptera: Formicidae). Methods: We aggregated data on species richness and island characteristics from previous studies on ant SARs to evaluate effects of climate, biogeographic realm, and latitude on slope values from these studies. A multimodel inference approach was used to determine the form of the different SARs, and whether there were any differences between mainland and insular SARs. We also assessed differences between mainland and insular SAR slopes and intercepts. To seek a general slope coefficient for ants, we used a mixed‐effect model. Finally, we tested for potential thresholds in the global insular SAR using piecewise regression models. Results: There was a negative relationship between SAR slopes and precipitation in both mainland and insular SARs, while SAR slopes and intercept values were higher in mainland compared to insular systems. Strong evidence of thresholds emerged in the global insular SAR. Finally, a general slope of 0.16 was observed for insular systems, which is lower than found in previous studies. Main Conclusions: A taxon‐focused approach proves to showcase unexpected patterns in the SAR. Ant diversity increases faster across area in mainland areas compared to true islands. The influences of climate and biogeographic realms on the ant SAR warrant deeper study. Our review highlights knowledge gaps in the ant SAR that also extend to other taxa, such as the effects of nonnative species on the SAR. [ABSTRACT FROM AUTHOR]

Habitat construction and phenotypic plasticity are alternative responses to variable environments. We explored evolution along an environmental gradient of habitat construction alone and in combination with phenotypic plasticity using individual‐based simulations that manipulated the fitness benefit of construction and whether construction maintained or eliminated that gradient. Construction was favored when its benefits were more likely to flow to the immediate offspring of the constructing individuals. Habitat construction and phenotypic plasticity traded off against each other or plasticity was selected against, depending on how the optimum environment varied and with the fitness value of construction. When selection favored differences in the amount of construction along the environmental gradient, genetic differentiation for habitat construction increased as the fitness value of construction increased. The degree to which each adaptive response was likely to evolve also depended on the precise ordering of life history events. Adaptive habitat construction does not always occur and may be selected against. [ABSTRACT FROM AUTHOR]

Threshold nonlinearities in the relationship between island area and species richness can result in dramatic declines in richness with a seemingly small decline in area near the threshold. What is not known, is whether threshold declines in richness are also accompanied by nonlinear changes in functional trait space and non‐random shifts of trait group composition in response to declining area.Plant species richness was recorded, and four functional diversity (FD) indices calculated based on 12 traits for 76 tree species in 5,082 plots (5 × 5 m) on 29 islands in the Thousand Island Lake region, Zhejiang, China. We tested for threshold nonlinearities in richness and FD relationships using segmented regression, with randomized resampling using a null model to account for potential sampling artefacts. We clustered tree species into trait groupings based on trait dissimilarity, and used multinomial segmented models to test whether threshold area effects on FD were associated with shifts in trait group composition.Species richness and three of the four FD indices showed significant threshold nonlinearities with declining island area below a threshold of ca 1.16–6.88 ha. K‐means clustering identified two trait groups, reflecting species at the 'fast' versus 'slow' ends of the trait spectrum. Significant area thresholds in trait group composition were driven by increasing relative richness, but decreasing relative abundance, of species with resource‐conservation traits on islands below the threshold.Synthesis. We found a threshold collapse in richness on islands below c. 1 ha, resulting in a significant decrease in functional trait space (functional richness) and an increase in the degree of niche differentiation among species in the community (functional divergence) on small islands. Threshold effects were associated with non‐random re‐assembly of trait group composition, favouring the relative richness of species at the 'slow' resource‐conservation end of the trait spectrum, but the relative abundance of a few species with 'fast' resource‐acquisition traits. These results suggest that disturbance‐driven dynamics potentially drive a functional shift in the ecosystem state at a critical threshold. We show that a minimum critical habitat area is required to maintain functional diversity in woody plant communities. [ABSTRACT FROM AUTHOR]

Evolutionary rescue occurs when genetic change allows a population to persist in response to an environmental change that would otherwise have led to extinction. Most studies of evolutionary rescue assume that species have either fully clonal or fully sexual reproduction; however, many species have partially clonal reproductive strategies in which they reproduce both clonally and sexually. Furthermore, the few evolutionary rescue studies that have evaluated partially clonal reproduction did not consider fluctuations in the environment, which are nearly ubiquitous in nature. Here, we use individual‐based simulations to investigate how environmental fluctuations (either uncorrelated or positively autocorrelated) influence the effect of clonality on evolutionary rescue. We show that, for moderate magnitudes of environmental fluctuations, as was found in the absence of fluctuations, increasing the degree of clonality increases the probability of population persistence in response to an abrupt environmental change, but decreases persistence in response to a continuous, directional environmental change. However, with large magnitudes of fluctuations, both the benefits of clonality following a step change and the detrimental effects of clonality following a continuous, directional change are generally reduced; in fact, in the latter scenario, increasing clonality can even become beneficial if environmental fluctuations are autocorrelated. We also show that increased generational overlap dampens the effects of environmental fluctuations. Overall, we demonstrate that understanding the evolutionary rescue of partially clonal organisms requires not only knowledge of the species life history and the type of environmental change, but also an understanding of the magnitude and autocorrelation of environmental fluctuations. [ABSTRACT FROM AUTHOR]

Hyperparasitism denotes the natural phenomenon where a parasite infecting a host is in turn infected by its own parasite. Hyperparasites can shape the dynamics of host-parasite interactions and often have a deleterious impact on pathogens, an important class of parasites, causing a reduction in their virulence and transmission rate. Hyperparasitism thus could be an important tool of biological control. However, host-parasite-hyperparasite systems have so far been outside the mainstream of modeling studies, especially those dealing with eco-evolutionary aspects of species interactions. Here, we theoretically explore the evolution of life-history traits in a generic host-parasite-hyperparasite system, focusing on parasite virulence and the positive impact that hyperparasitism has on the host population. We also explore the coevolution of life-history traits of the parasite and hyperparasite, using adaptive dynamics and quantitative genetics frameworks to identify evolutionarily singular strategies. We find that in the presence of hyperparasites, the evolutionarily optimal pathogen virulence generally shifts toward more virulent strains. However, even in this case the use of hyperparasites in biocontrol could be justified, since overall host mortality decreases. An intriguing possible outcome of the evolution of the hyperparasite can be its evolutionary suicide. [ABSTRACT FROM AUTHOR]

Substantial environmental change can force a population onto a path towards extinction, but under some conditions, adaptation by natural selection can rescue the population and allow it to persist. This process, known as evolutionary rescue, is believed to be less likely to occur with greater magnitudes of random environmental fluctuations because environmental variation decreases expected population size, increases variance in population size and increases evolutionary lag. However, previous studies of evolutionary rescue in fluctuating environments have only considered scenarios in which evolutionary rescue was likely to occur. We extend these studies to assess how baseline extinction risk (which we manipulated via changes in the initial population size, degree of environmental change or mutation rate) influences the effects of environmental variation on evolutionary rescue following an abrupt environmental change. Using a combination of analytical models and stochastic simulations, we show that autocorrelated environmental variation hinders evolutionary rescue in low-extinction-risk scenarios but facilitates rescue in high-risk scenarios. In these high-risk cases, the chance of a run of good years counteracts the otherwise negative effects of environmental variation on evolutionary demography. These findings can inform the development of effective conservation practices that consider evolutionary responses to abrupt environmental changes. [ABSTRACT FROM AUTHOR]

Non-native invasive plants can establish in natural areas, where they can be ecologically damaging and costly to manage. Like cultivated plants, invasive plants can experience a relatively disease-free period upon introduction and accumulate pathogens over time. Diseases of invasive plant populations are infrequently studied compared to diseases of agriculture, forestry, and even native plant populations. We evaluated similarities and differences in the processes that are likely to affect pathogen accumulation and disease in invasive plants compared to cultivated plants, which are the dominant focus of the field of plant pathology. Invasive plants experience more genetic, biotic, and abiotic variation across space and over time than cultivated plants, which is expected to stabilize the ecological and evolutionary dynamics of interactions with pathogens and possibly weaken the efficacy of infectious disease in their control. Although disease is expected to be context dependent, the widespread distribution of invasive plants makes them important pathogen reservoirs. Research on invasive plant diseases can both protect crops and help manage invasive plant populations. [ABSTRACT FROM AUTHOR]

Aim: We evaluated different facets of beta diversity (taxonomic, phylogenetic and functional), and its components (spatial turnover and nestedness), of a stream macroalgal metacommunity, as well as the effect of local environmental variables, types of biome and spatial factors on these facets and components. Location: Ten natural areas of southern Brazil, covering the main biomes represented in the region. Taxon: Stream macroalgae. Methods: We analysed a macroalgal data set collected in 105 stream segments using a dissimilarity partitioning approach to decompose total beta diversity into spatial turnover and nestedness components. Furthermore, we assessed the effects of local environmental variables, biome type and spatial factors on beta diversity components by performing distance‐based redundancy analysis (db‐RDA), and its partial version (db‐pRDA). Taxonomic data were tabulated considering four different species incidence matrices: total macroalgae; only green algae; only red algae and only cyanobacteria. Results: For taxonomic and phylogenetic facets, very high values of total beta diversity were found for all species incidence matrices, with spatial turnover (species replacement) accounting for almost all this diversity; nestedness had extremely low values. For functional diversity, total beta diversity was again high and spatial turnover was greater than nestedness, but nestedness (the tendency for less diverse locations to contain a subset of those in higher diversity locations) was considerably higher than that observed for taxonomic and phylogenetic facets. In regard to taxonomic and phylogenetic facets, total beta diversity and spatial turnover were, in general, significantly related to local environmental variables, biome type and spatial factors for total macroalgae and green algae, whereas they were significantly related to types of biome and space for red algae, and only to local environment for cyanobacteria. Main conclusions: Our results showed that spatial turnover was the main component of beta diversity, regardless of the facet and macroalgal species incidence matrix, and that the relative influence of local environmental variables, types of biome and spatial factors on the total beta diversity and its spatial turnover component can vary according to the facet considered and by algal group. [ABSTRACT FROM AUTHOR]

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Environmental factors control spatial distributions and local abundances in distinct – but overlapping – ways. Osorio‐Olivera et al. examine when environments near the geometric center of a species' ecological niche – which they assume to be optimal for growth when rare – also harbor the greatest number of individuals on average at equilibrium, and when not. Transient dynamics, Allee effects and metapopulation dynamics can cloud this relationship. In this brief piece I sketch a number of further ways in which this relationship can break down, including asymmetry in the shape of the niche, spatial variation in density dependence, and nonlinear feedbacks with the environment. [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]

The role of biotic interactions in shaping the distribution and abundance of species should be particularly pronounced in symbionts. Indeed, symbionts have a dual niche composed of traits of their individual hosts and the abiotic environment external to the host, and often combine active dispersal at finer scales with host‐mediated dispersal at broader scales. The biotic complexity in the determinants of species distribution and abundance should be even more pronounced for hyper symbionts (symbionts of other symbionts).We use a chain of symbiosis to explore the relative influence of nested biotic interactions and the abiotic environment on occupancy and abundance of a hypersymbiont.Our empirical system is the epibiont ciliate Lagenophrys discoidea, which attaches to an ostracod that is itself ectosymbiotic on crayfish (the basal host). We applied multimodel selection and variance partitioning for GLMM to assess the relative importance of (a) traits of symbiotic hosts (ostracod sex and abundance), (b) traits of basal hosts (crayfish body weight, abundance and intermoult stage), (c) the abiotic environment (water chemistry and climate) and (d) geospatial autocorrelation patterns (capturing potential effects of crayfish dispersal among localities).Our models explained about half of the variation in prevalence and abundance of the hypersymbiont. Variation in prevalence was partly explained, in decreasing order of importance (18%–4%) by shared effects of symbiotic host traits and the abiotic environment, pure fixed effects of symbiotic hosts, abiotic environment and geospatial patterns (traits of basal hosts were not relevant). Hypersymbiont abundance was most strongly explained by random effects of host traits (mainly the symbiotic host), in addition to weaker fixed effects (mostly abiotic environment).Our results highlight the major role of the interplay between abundance of symbiotic hosts and water physico‐chemistry in regulating populations of a hypersymbiotic ciliate, which is likely critical for dispersal dynamics, availability of attachment resources and suitability of on‐host living conditions for the ciliate. We also found moderate signal of regulation by the basal host, for which we propose three mechanisms: (a) modulation of microhabitat suitability (crayfish‐created water currents); (b) concentration of symbiotic hosts within crayfish; and (c) dispersal mediated by crayfish. [ABSTRACT FROM AUTHOR]

Populations subject to substantial environmental change that decreases absolute fitness (expected number of offspring per individual) to less than one must adapt to persist. The probability of adaptive evolutionary rescue may be influenced by factors intrinsic to the organism itself, or by features specific to the individual population and its environment. An important question (given the increasing prevalence of environmental change) is the predictability of evolutionary rescue. We used an individual-based simulation model and a related analytic model to examine population persistence, given a continuously changing environment that leads to a linear change in the optimum for a phenotypic trait under selection. Population persistence was not well predicted by the population genetics at the start of environmental change, which contrasts strongly with the results shown in prior work for persistence after a sudden environmental change. Larger populations, which had a greater scope for the generation and maintenance of beneficial genetic variation, showed a clear advantage, but increasing the rate of environmental change always decreased the probability of persistence. Extinctions occurred throughout the period of continuous change, and populations that went extinct showed little sign of their eventual fate until shortly before extinction. Partially clonal populations showed less predictability and greater vulnerability to extinction when impacted by continuous change than did fully sexual populations—any advantage gained by the initial transmission of well-adapted phenotypes via clonal reproduction is lost as the phenotypic optimum continues to shift and the generation of novel variation is required for continuous adaptation. [ABSTRACT FROM AUTHOR]

Predicting connectivity, or how landscapes alter movement, is essential for understanding the scope for species persistence with environmental change. Although it is well known that movement is risky, connectivity modelling often conflates behavioural responses to the matrix through which animals disperse with mortality risk. We derive new connectivity models using random walk theory, based on the concept of spatial absorbing Markov chains. These models decompose the role of matrix on movement behaviour and mortality risk, can incorporate species distribution to predict the amount of flow, and provide both short‐ and long‐term analytical solutions for multiple connectivity metrics. We validate the framework using data on movement of an insect herbivore in 15 experimental landscapes. Our results demonstrate that disentangling the roles of movement behaviour and mortality risk is fundamental to accurately interpreting landscape connectivity, and that spatial absorbing Markov chains provide a generalisable and powerful framework with which to do so. [ABSTRACT FROM AUTHOR]

In nature, rates of dispersal vary greatly over time, yet most theoretical explorations of ecological and evolutionary dynamics to date have assumed constant movement rates. Here we examine how a particular pattern of temporal variation—periodic pulses of immigration—influences adaptation to a harsh environment, in which a species experiences conditions outside its niche requirements. Using both deterministic models and stochastic individual-based simulations, we show that for many ecological and genetic scenarios, temporally spacing out immigration events increases the probability that local adaptation is sufficient for persistence (i.e., niche evolution). When immigration events are too frequent, gene flow can hamper local adaptation in sexual species, but sufficiently infrequent pulses of immigration allow for repeated opportunities for adaptation with temporary escapes from gene flow during which local selection is unleashed. We develop versions of our models with and without density dependence for three different assumptions about the genetics underlying fitness (haploid, diploid, and quantitative genetic variation) so that our results may be applicable to a wide range of natural systems. Our study adds to a growing body of literature showing that temporal variation in migration rates can have significant effects on local adaptation and is among the first to show how such variation affects niche evolution. [ABSTRACT FROM AUTHOR]

COMMENTARY Towardecoevolutionarydynamics Karl Sigmund a,1 and Robert D. Holt b  AsbiologistAndrewHendryrecentlywrote,"research initiatives in ecology and evolution have periodically dated but never married" (1). Maynard Smith was the first to apply this insight to the frequency-dependent selection of phenotypic traits, using game theory (5). Ecoevolution The relation of evolution with ecology seems more promising (1, 9).Thesuccessofagiventraitoftendependsonthefrequencyof some trait in another population, as well as on population densities. Evolutionary Game Theory Often, the success of a trait depends on the trait values of other members of its population, and on their abundance. [Extracted from the article]

Exotic species are often predicted to successfully invade when their functional traits differ from species in recipient communities. Many studies have related trait differences among natives and invaders to competitive outcomes. Few studies, however, have tested whether functionally similar invaders have similar competitive impacts on natives. We investigated interactions in communities of a native annual forb Waitzia acuminata (Asteraceae) and two invasive annual grasses that are ecologically similar and co-occur in southwestern Australia. Using a combination of field and laboratory experiments and several performance measures, we assessed impacts of these grasses on W. acuminata. We also examined differences among species in their responses to intraspecific versus interspecific competition, including their frequency dependence. The two similar exotic grasses differed in interaction impacts, with one facilitating and the other suppressing the native. In general, intraspecific competition was stronger than interspecific competition for the native, while evidence of competition was weak for the exotics. These patterns may reflect that W. acuminata does well in these communities due to the combined impacts of stabilization and facilitation, whereas the exotics benefit from limited stabilization (mediated by their weak intraspecific competition) or weak interspecific competition with W. acuminata. We found divergent impacts of the exotic species despite their similar functional traits. We demonstrate that a native species may benefit from interactions with an exotic "benefactor" species, highlighting the potential importance of positive interactions in invaded communities. Our findings underscore the necessity of considering neutral and positive interactions in addition to competition in understanding invasion dynamics in real plant communities. [ABSTRACT FROM AUTHOR]

Explaining the maintenance of tropical forest diversity under the countervailing forces of drift and competition poses a major challenge to ecological theory. Janzen-Connell effects, in which host-specific natural enemies restrict the recruitment of juveniles near conspecific adults, provide a potential mechanism. Janzen-Connell is strongly supported empirically, but existing theory does not address the stable coexistence of hundreds of species. Here we use high-performance computing and analytical models to demonstrate that tropical forest diversity can be maintained nearly indefinitely in a prolonged state of transient dynamics due to distance-responsive natural enemies. Further, we show that Janzen-Connell effects lead to community regulation of diversity by imposing a diversitydependent cost to commonness and benefit to rarity. The resulting species-area and rank-abundance relationships are consistent with empirical results. Diversity maintenance over long time spans does not require dispersal from an external metacommunity, speciation, or resource niche partitioning, only a small zone around conspecific adults in which saplings fail to recruit. We conclude that the Janzen-Connell mechanism can explain the maintenance of tropical tree diversity while not precluding the operation of other nichebased mechanisms such as resource partitioning. [ABSTRACT FROM AUTHOR]

Natural enemies, that is, species that inflict harm on others while feeding on them, are fundamental drivers of biodiversity dynamics and represent a substantial portion of biodiversity as well. Along the life history of the Earth, natural enemies have been involved in probably some of the most productive mechanisms of biodiversity genesis; that is, adaptive radiation mediated by enemy-victim coevolutionary processes. At ecological timescales, natural enemies are a fundamental piece of food webs and can contribute to biodiversity preservation by promoting stability and coexistence at lower trophic levels through top-down regulation mechanisms. However, natural enemies often produce dramatic losses of biodiversity, especially when humans are involved. [ABSTRACT FROM AUTHOR]

This paper introduces a novel partial differential equation immuno-eco-epidemiological model of competition in which one species is affected by a disease while another can compete with it directly and by lowering the first species' immune response to the infection, a mode of competition termed stress-induced competition. When the disease is chronic, and the within-host dynamics are rapid, we reduce the partial differential equation model (PDE) to a three-dimensional ordinary differential equation (ODE) model. The ODE model exhibits backward bifurcation and sustained oscillations caused by the stress-induced competition. Furthermore, the ODE model, although not a special case of the PDE model, is useful for detecting backward bifurcation and oscillations in the PDE model. Backward bifurcation related to stress-induced competition allows the second species to persist for values of its invasion number below one. Furthermore, stress-induced competition leads to destabilization of the coexistence equilibrium and sustained oscillations in the PDE model. We suggest that complex systems such as this one may be studied by appropriately designed simple ODE models. [ABSTRACT FROM AUTHOR]

Successful public health regimes for COVID-19 push below unity longterm regional Rt --the average number of secondary cases caused by an infectious individual. We use a susceptible-infectious-recovered (SIR) model for two coupled populations to make the conceptual point that asynchronous, variable local control, together with movement between populations, elevates long-term regional Rt, and cumulative cases, and may even prevent disease eradication that is otherwise possible. For effective pandemic mitigation strategies, it is critical that models encompass both spatiotemporal heterogeneity in transmission and movement. [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]

The article focuses on role of emergence and accumulation of pathogens on non-native plant invaders in promoting native species recovery. It states findings of a study indicating accumulation of pathogens and reduced performance of a widespread invader due to infectious disease, and mentions that s research published in the issue which concludes that pathogen accumulation cannot reverse the impacts of invasive plants. It notes that outcome of pathogen emergence is difficult to predict.

Most species have one or more natural enemies, e.g., predators, parasites, pathogens, and herbivores, among others. These species in turn typically attack multiple victim species. This leads to the possibility of indirect interactions among those victims, both positive and negative. The term apparent competition commonly denotes negative indirect interactions between victim species that arise because they share a natural enemy. This indirect interaction, which in principle can be reflected in many facets of the distribution and abundance of individual species and more broadly govern the structure of ecological communities in time and space, pervades many natural ecosystems. It also is a central theme in many applied ecological problems, including the control of agricultural pests, harvesting, the conservation of endangered species, and the dynamics of emerging diseases. At one end of the scale of life, apparent competition characterizes intriguing aspects of dynamics within individual organisms-for example, the immune system is akin in many ways to a predator that can induce negative indirect interactions among different pathogens. At intermediate scales of biological organization, the existence and strength of apparent competition depend upon many contingent details of individual behavior and life history, as well as the community and spatial context within which indirect interactions play out. At the broadest scale of macroecology and macroevolution, apparent competition may play a major, if poorly understood, role in the evolution of species' geographical ranges and adaptive radiations. [ABSTRACT FROM AUTHOR]

We used an individual-based simulation model to examine the role of phenotypic plasticity on persistence and adaptation to two patterns of environmental variation, a single, abrupt step change and continual, linear change. Our model tested the assumptions and predictions of the theory of genetic assimilation, explored the evolutionary dynamics of the Baldwin effect, and provided expectations for the evolutionary response to climate change. We found that genetic assimilation as originally postulated is not likely to occur because the replacement of plasticity by fixed genetic effects takes much longer than the environment is likely to remain stable. On the other hand, trait plasticity as an enhancement to continual evolutionary change may be an important evolutionary mechanism as long as plasticity has little or no costs. Whether or not plasticity helps or hinders evolutionary rescue following a step change in the environment depends on whether plasticity is costly. For linear environmental change, noncostly plasticity always decreases extinction rates, while costly plasticity can create a fitness drag and increase the chance of extinction. Thus, with changing climates plasticity can enhance adaptation and prevent extinction under some conditions, but not others. [ABSTRACT FROM AUTHOR]

Evolutionary lag--the difference between mean and optimal phenotype in the current environment--is of keen interest in light of rapid environmental change. Many ecologically important organisms have life histories that include stage structure and both sexual and clonal reproduction, yet how stage structure and clonality interplay to govern a population's rate of evolution and evolutionary lag is unknown. Effects of clonal reproduction on mean phenotype partition into two portions: one that is phenotype dependent, and another that is genotype dependent. This partitioning is governed by the association between the nonadditive genetic plus random environmental component of phenotype of clonal offspring and their parents. While clonality slows phenotypic evolution toward an optimum, it can dramatically increase population survival after a sudden step change in optimal phenotype. Increased adult survival slows phenotypic evolution but facilitates population survival after a step change; this positive effect can, however, be lost given survival-fecundity trade-offs. Simulations indicate that the benefits of increased clonality under environmental change greatly depend on the nature of that change: increasing population persistence under a step change while decreasing population persistence under a continuous linear change requiring de novo variation. The impact of clonality on the probability of persistence for species in a changing world is thus inexorably linked to the temporal texture of the change they experience. [ABSTRACT FROM AUTHOR]

Herbivory has long been recognized as a significant driver of plant population dynamics, yet its effects along environmental gradients are unclear. Understanding how weather modulates plant-insect interactions can be particularly important for predicting the consequences of exotic insect invasions, and an explicit consideration of weather may help explain why the impact can vary greatly across space and time. We surveyed two native prickly pear cactus species (genus Opuntia) in the Florida panhandle, USA, and their specialist insect herbivores (the invasive South American cactus moth, Cactoblastis cactorum, and three native insect species) for five years across six sites. We used generalized linear mixed models to assess the impact of herbivory and weather on plant relative growth rate ( RGR) and sexual reproduction, and we used Fisher's exact test to estimate the impact of herbivory on survival. Weather variables (precipitation and temperature) were consistently significant predictors of vital rate variation for both cactus species, in contrast to the limited and varied impacts of insect herbivory. Weather only significantly influenced the impact of herbivory on Opuntia humifusa fruit production. The relationships of RGR and fruit production with precipitation suggest that precipitation serves as a cue in determining the trade-off in the allocation of resources to growth or fruit production. The presence of the native bug explained vital rate variation for both cactus species, whereas the invasive moth explained variation only for O. stricta. Despite the inconsistent effect of herbivory across vital rates and cactus species, almost half of O. stricta plants declined in size, and the invasive insect negatively affected RGR and fruit production. Given that fruit production was strongly size-dependent, this suggests that O. stricta populations at the locations surveyed are transitioning to a size distribution of predominantly smaller sizes and with reduced sexual reproduction potential. [ABSTRACT FROM AUTHOR]

Ilkka Hanski is most widely known for his seminal contributions to metapopulation ecology, both theoretical and empirical. But he also made many important and wide-ranging contributions to other arenas of ecological inquiry, including in particular predator-prey, host-parasitoid, and host-pathogen interactions. This paper provides an overview of his work in trophic ecology, ranging from individual behavior of foraging predators and fleeing prey, up to effects of spatial patchiness on the persistence of specialist natural enemies, and even the determinants of food chain length. In recent years, his work on food web interactions took on an increasingly genetic and evolutionary slant. In this paper, I also return to two theoretical models that I discussed over the years with Ilkka, where we contemplated carrying out collaborative work, but never managed to do so. The first of these models involves how habitat patchiness might moderate apparent competition between prey species. The second of these has to do with splicing evolutionary dynamics into metapopulation models, so as to craft hypotheses about how food chain length might be influenced by the coevolutionary struggle between predators and their prey. I developed simple models of the sort we should have explored together, in the style we would have used at the time of our conversations on these themes, in homage to my memory of our interactions. [ABSTRACT FROM AUTHOR]

It is widely recognized that ecological dynamics influence evolutionary dynamics, and conversely that evolutionary changes alter ecological processes. Because fragmentation impacts all biological levels (from individuals to ecosystems) through isolation and reduced habitat size, it strongly affects the links among evolutionary and ecological processes such as population dynamics, local adaptation, dispersal and speciation. Here, we review our current knowledge of the eco-evolutionary dynamics in fragmented landscapes, focusing on both theory and experimental studies. We then suggest future experimental directions to study eco-evolutionary dynamics and/or feedbacks in fragmented landscapes, especially to bridge the gap between theoretical predictions and experimental validations. [ABSTRACT FROM AUTHOR]