Thermal responses of feeding rates differ across co-occurring predator species.

Changes in global temperature regimes are expected to transform species interactions in natural communities. However, predicting the consequences of warming on populations and communities is challenging because species interact with a range of community members. In theory, species should be adapted to their local temperature regimes, which might suggest a parallel shift across species interactions.

Strengthening of negative density dependence mediates population decline at high temperatures.

While temperature is well known to affect many life history traits of ectothermic organisms, any attempt to scale up these individual-level processes to population-level consequences must assume a relationship between temperature and the strength of per capita density dependence. Yet, theory has made contrasting predictions about this relationship, and we still need clear experimental tests to determine which relationship is realized in natural systems, especially in heterotrophs. Here, we experimentally isolated and quantified the thermal response of density dependence from the population dynamics of the herbivore Daphnia pulex.

Time is of the essence: A general framework for uncovering temporal structures of communities.

Ecological communities are inherently dynamic: species constantly turn over within years, months, weeks or even days. These temporal shifts in community composition determine essential aspects of species interactions and how energy, nutrients, information, diseases and perturbations 'flow' through systems. Yet, our understanding of community structure has relied heavily on static analyses not designed to capture critical features of this dynamic temporal dimension of communities.

Time-dependent interaction modification generated from plant-soil feedback.

Pairwise interactions between species can be modified by other community members, leading to emergent dynamics contingent on community composition. Despite the prevalence of such higher-order interactions, little is known about how they are linked to the timing and order of species' arrival. We generate population dynamics from a mechanistic plant-soil feedback model, then apply a general theoretical framework to show that the modification of a pairwise interaction by a third plant depends on its germination phenology.

Predation and competition drive trait diversity across space and time.

Competition should play a key role in shaping community assembly and thereby local and regional biodiversity patterns. However, identifying its relative importance and effects in natural communities is challenging because theory suggests that competition can lead to different and even opposing patterns depending on the underlying mechanisms. Here, we have taken a different approach: rather than attempting to indirectly infer competition from diversity patterns, we compared trait diversity patterns in odonate (dragonfly and damselfly) communities across different spatial and temporal scales along a natural competition-predation gradient.

Stage-mediated priority effects and season lengths shape long-term competition dynamics.

The relative arrival time of species can affect their interactions and thus determine which species persist in a community. Although this phenomenon, called priority effect, is widespread in natural communities, it is unclear how it depends on the length of growing season. Using a seasonal stage-structured model, we show that differences in stages of interacting species could generate priority effects by altering the strength of stabilizing and equalizing coexistence mechanisms, changing outcomes between exclusion, coexistence and positive frequency dependence.

Bridging theory and experiments of priority effects.

Priority effects play a key role in structuring natural communities, but considerable confusion remains about how they affect different ecological systems. Synthesizing previous studies, we show that this confusion arises because the mechanisms driving priority and the temporal scale at which they operate differ among studies, leading to divergent outcomes in species interactions and biodiversity patterns. We suggest grouping priority effects into two functional categories based on their mechanisms: frequency-dependent priority effects that arise from positive frequency dependence, and trait-dependent priority effects that arise from time-dependent changes in interacting traits.

Priority Effects Determine How Dispersal Affects Biodiversity in Seasonal Metacommunities.

AbstractThe arrival order of species frequently determines the outcome of their interactions. This phenomenon, called the priority effect, is ubiquitous in nature and determines local community structure, but we know surprisingly little about how it influences biodiversity across different spatial scales. Here, we use a seasonal metacommunity model to show that biodiversity patterns and the homogenizing effect of high dispersal depend on the specific mechanisms underlying priority effects.

Exploring Conditions That Strengthen or Weaken the Ecological and Evolutionary Consequences of Phenological Synchrony.

AbstractClimate change-driven phenological shifts alter the temporal distributions of natural populations and communities, but we have little understanding of how these shifts affect natural populations. Using agent-based models, we show that the interaction of within-population synchrony (individual variation in timing) and timing of interspecific interactions shapes ecological and evolutionary dynamics of populations within a seasonal cycle. Low-synchrony populations had lower survival and biomass but relatively stronger individuals.

Climate warming promotes pesticide resistance through expanding overwintering range of a global pest.

Climate change has the potential to change the distribution of pests globally and their resistance to pesticides, thereby threatening global food security in the 21st century. However, predicting where these changes occur and how they will influence current pest control efforts is a challenge. Using experimentally parameterised and field-tested models, we show that climate change over the past 50 years increased the overwintering range of a global agricultural insect pest, the diamondback moth (Plutella xylostella), by ~2.

Developmental Change in Predators Drives Different Community Configurations.

AbstractTheoreticians who first observed alternative stable states in simple ecological models warned of grave implications for unexpected and irreversible collapses of natural systems (i.e., regime shifts).

Ontogenetic diversity buffers communities against consequences of species loss.

Biodiversity can be measured at multiple organizational scales. While traditional studies have focused at taxonomic diversity, recent studies have emphasized the ecological importance of diversity within populations. However, it is unclear how these different scales of diversity interact to determine the consequence of species loss.

Within-host priority effects and epidemic timing determine outbreak severity in co-infected populations.

Co-infections of hosts by multiple pathogen species are ubiquitous, but predicting their impact on disease remains challenging. Interactions between co-infecting pathogens within hosts can alter pathogen transmission, with the impact on transmission typically dependent on the relative arrival order of pathogens within hosts (within-host priority effects). However, it is unclear how these within-host priority effects influence multi-pathogen epidemics, particularly when the arrival order of pathogens at the host-population scale varies.

How parasite interaction strategies alter virulence evolution in multi-parasite communities.

The majority of organisms host multiple parasite species, each of which can interact with hosts and competitors through a diverse range of direct and indirect mechanisms. These within-host interactions can directly alter the mortality rate of coinfected hosts and alter the evolution of virulence (parasite-induced host mortality). Yet we still know little about how within-host interactions affect the evolution of parasite virulence in multi-parasite communities.

Shifts in phenological mean and synchrony interact to shape competitive outcomes.

Climate change-induced phenological shifts are ubiquitous and have the potential to disrupt natural communities by changing the timing of species interactions. Shifts in first and/or mean phenological date are well documented, but recent studies indicate that shifts in synchrony (individual variation around these metrics) can be just as common. However, we know little about how both types of phenological shifts interact to affect species interactions and communities.

Phenotype-Environment Matching Predicts Both Positive and Negative Effects of Intraspecific Variation.

Natural populations can vary considerably in their genotypic and/or phenotypic diversity. Differences in this intraspecific diversity can have important consequences for contemporary ecological dynamics, but the direction and magnitude of these effects appear inconsistent across studies and systems. Here we proposed and tested the hypothesis that context-dependent ecological effects of altering phenotypic variance are predictable and arise from the relationship between a population's mean phenotype and the local environmental optimum.

Opportunities for behavioral rescue under rapid environmental change.

Laboratory measurements of physiological and demographic tolerances are important in understanding the impact of climate change on species diversity; however, it has been recognized that forecasts based solely on these laboratory estimates overestimate risk by omitting the capacity for species to utilize microclimatic variation via behavioral adjustments in activity patterns or habitat choice. The complex, and often context-dependent nature, of microclimate utilization has been an impediment to the advancement of general predictive models. Here, we overcome this impediment and estimate the potential impact of warming on the fitness of ectotherms using a benefit/cost trade-off derived from the simple and broadly documented thermal performance curve and a generalized cost function.

The role of seasonal timing and phenological shifts for species coexistence.

Shifts in the phenologies of coexistence species are altering the temporal structure of natural communities worldwide. However, predicting how these changes affect the structure and long-term dynamics of natural communities is challenging because phenology and coexistence theory have largely proceeded independently. Here, I propose a conceptual framework that incorporates seasonal timing of species interactions into a well-studied competition model to examine how changes in phenologies influence long-term dynamics of natural communities.

Within-Host Priority Effects Systematically Alter Pathogen Coexistence.

Coinfection of host populations alters pathogen prevalence, host mortality, and pathogen evolution. Because pathogens compete for limiting resources, whether multiple pathogens can coexist in a host population can depend on their within-host interactions, which, in turn, can depend on the order in which pathogens infect hosts (within-host priority effects). However, the consequences of within-host priority effects for pathogen coexistence have not been tested.

Prey Limitation Drives Variation in Allometric Scaling of Predator-Prey Interactions.

Ecologists have long searched for a universal size-scaling constant that governs trophic interactions. Although this is an appealing theoretical concept, predator-prey size ratios (PPSRs) vary strikingly across and within natural food webs, meaning that predators deviate from their optimal prey size by consuming relatively larger or smaller prey. Here we suggest that this unexpected variation in allometric scaling of trophic interactions can be predicted by gradients of prey limitation consistent with predictions from optimal foraging theory.

Resource limitation alters effects of phenological shifts on inter-specific competition.

Phenological shifts can alter the relative arrival time of competing species in natural communities, but predicting the consequences for species interactions and community dynamics is a major challenge. Here we show that differences in relative arrival time can lead to predictable priority effects that alter the outcome of competitive interactions. By experimentally manipulating the relative arrival time of two competing tadpole species across a resource gradient, we found that delaying relative arrival of a species reduced the interaction asymmetry between species and could even reverse competitive dominance.

Drivers of individual niche variation in coexisting species.

Although neglected by classic niche theory, individual variation is now recognized as a prevalent phenomenon in nature with evolutionary and ecological relevance. Recent theory suggests that differences in individual variation across competitors can affect species coexistence and community patterns. However, the degree of individual variation is flexible across wild populations and we still know little about the ecological drivers of this variation across populations of single species and, especially, across coexisting species.

Shifts in phenological distributions reshape interaction potential in natural communities.

Climate change has changed the phenologies of species worldwide, but it remains unclear how these phenological changes will affect species interactions and the structure of natural communities. Using a novel approach to analyse long-term data of 66 amphibian species pairs across eight communities, we demonstrate that phenological shifts can significantly alter the interaction potential of coexisting competitors. Importantly, these changes in interaction potential were mediated by non-uniform, species-specific shifts in entire phenological distributions and consequently could not be captured by metrics traditionally used to quantify phenological shifts.

Nonlinear effects of phenological shifts link interannual variation to species interactions.

The vast majority of species interactions are seasonally structured and depend on species' relative phenologies. However, differences in the phenologies of species naturally vary across years and are altered by ongoing climate change around the world. By combining experiments that shifted the relative hatching of two competing tadpole species across a productivity gradient with simulations of inter-annual variation in arrival times I tested how phenological variation across years can alter the strength and outcome of interspecific competition.