Predators can influence the host-parasite dynamics of their prey via nonconsumptive effects.

Ecological communities are partly structured by indirect interactions, where one species can indirectly affect another by altering its interactions with a third species. In the absence of direct predation, nonconsumptive effects of predators on prey have important implications for subsequent community interactions. To better understand these interactions, we used a -parasite-predator cue system to evaluate if predation risk affects responses to a parasite.

Gender underlies the formation of STEM research groups.

Research groups are the cornerstone of scientific research, yet little is known about how these groups are formed and how their organization is influenced by the gender of the research group leader. This represents an important gap in our understanding of the processes shaping gender structure within universities and the academic fields they represent. Here, we report the results of an email survey sent to department chairs and discipline-specific listservs.

Abundance and traits link predator ontogeny to prey communities.

Function and abundances shape species interactions and thus ecological communities. While communities are often summarized as the mean function of each species, intraspecific variation in traits and thus function is an important driver of community composition. Ontogeny is a common source of intraspecific variation, but while age-related functional changes can alter species interactions, so too can the effects of those functions on the density of the focal organism.

Ecological and Evolutionary Stochasticity Shape Natural Selection.

The distribution of biodiversity depends on the combined and interactive effects of ecological and evolutionary processes. The joint contribution of these processes has focused almost exclusively on deterministic effects, even though mechanisms that increase the importance of random ecological processes are expected to also increase the importance of random evolutionary processes. Here we manipulate the sizes of old field fragments to generate correlated sampling effects for a focal population (a gall maker) and its enemy community.

Ecological rigidity and the hardness of selection in the wild.

Hutchinson's ecological theater and evolutionary play is a classical view of evolutionary ecology-ecology provides a template in which evolution occurs. An opposing view is that ecological and evolutionary changes are like two actors on a stage, intertwined by density and frequency dependence. These opposing views correspond to hard and soft selection, respectively.

Urbanization reshapes a food web.

Cities represent humanity's most intense impact on our planet, with more than half of all humans now residing in urban areas. Indeed, urbanization has well-understood impacts on both individual species and general patterns of biodiversity. However, species do not exist in isolation, but are instead members of complex interaction networks that shape patterns of diversity and influence ecosystem services.

Individual and Population Differences Shape Species Interactions and Natural Selection.

Trait variation is central to our understanding of species interactions, and trait variation arising within species is increasingly recognized as an important component of community ecology. Ecologists generally consider intraspecific variation either among or within populations, yet these differences can interact to create patterns of species interactions. These differences can also affect species interactions by altering processes occurring at distinct scales.

Trait variation across biological scales shapes community structure and ecosystem function.

Trait variation underlies our understanding of the patterns and importance of biodiversity, yet we have a poor understanding of how variation at different levels of biological organization structures communities and ecosystems. Here, we use a mesocosm experiment to test for the effects of a larval dragonfly functional trait on community and ecosystem dynamics by creating artificial populations to mirror within- and between-population trait variation observed in our study area. Specifically, we manipulate variation in activity rate, a key functional trait shaping food webs, across three levels of biological organization: within-populations (differences in trait variation in a population), among-populations (differences in population mean trait values), and among-species (species-level differences of co-occurring dragonflies).

Host traits and competitive ability jointly structure disease dynamics and community assembly.

Parasitism and competition are both ubiquitous interactions in ecological communities. The ability of host species to interact directly via competition and indirectly through shared parasites suggests that host traits related to competition and parasitism are likely important in structuring communities and disease dynamics. Specifically, those host traits affecting competition and those mediating parasitism are often correlated either because of trade-offs (in resource acquisition or resource allocation) or condition dependence, yet the consequences of these trait relationships for community and epidemiological dynamics are poorly understood.

Indirect Interactions Shape Selection in a Multispecies Food Web.

Species do not live, interact, or evolve in isolation but are instead members of complex ecological communities. In ecological terms, complex multispecies interactions can be understood by considering indirect effects that are mediated by changes in traits and abundances of intermediate species. Interestingly, traits and abundances are also central to our understanding of phenotypic selection, suggesting that indirect effects may be extended to understand evolution in complex communities.

Sexual dimorphism in a top predator () drives aquatic prey community assembly.

Intraspecific variation can have important consequences for the structure and function of ecological communities, and serves to link community ecology to evolutionary processes. Differences between the sexes are an overwhelmingly common form of intraspecific variation, but its community-level consequences have never been experimentally investigated. Here, we manipulate the sex ratio of a sexually dimorphic predacious newt in aquatic mesocosms, then track their impact on prey communities.

Ontogeny and Consistent Individual Differences Mediate Trophic Interactions.

Ecologists use species traits to predict responses to environmental change and, ultimately, to understand the composition of biological communities. However, this ignores known and substantial intraspecific variation that can have important consequences for species interactions and community composition. This within-species variation results from two distinct sources: ontogeny and consistent individual differences.

Predator macroevolution drives trophic cascades and ecosystem functioning.

Biologists now recognize that ecology can drive evolution, and that evolution in turn produces ecological patterns. I extend this thinking to include longer time scales, suggesting that macroevolutionary transitions can create phenotypic differences among species, which then have predictable impacts on species interactions, community assembly and ecosystem functioning. Repeated speciation can exacerbate these patterns by creating communities with similar phenotypes and hence ecological impacts.

Consumer-resource interactions along urbanization gradients drive natural selection.

Urbanization is an important component of global change. Urbanization affects species interactions, but the evolutionary implications are rarely studied. We investigate the evolutionary consequences of a common pattern: the loss of high trophic-level species in urban areas.

Physiology underlies the assembly of ecological communities.

Trait-based community ecology promises an understanding of the factors that determine species abundances and distributions across habitats. However, ecologists are often faced with large suites of potentially important traits, making generalizations across ecosystems and species difficult or even impossible. Here, we hypothesize that key traits structuring ecological communities may be causally dependent on common physiological mechanisms and that elucidating these mechanisms can help us understand the distributions of traits and species across habitats.

Animal behaviour and algal camouflage jointly structure predation and selection.

Trait variation can structure interactions between individuals, thus shaping selection. Although antipredator strategies are an important component of many aquatic systems, how multiple antipredator traits interact to influence consumption and selection remains contentious. Here, I use a common larval dragonfly (Epitheca canis) and its predator (Anax junius) to test for the joint effects of activity rate and algal camouflage on predation and survival selection.

Keystone Individuals Alter Ecological and Evolutionary Consumer-Resource Dynamics.

Intraspecific variation is central to our understanding of evolution and ecology, but these fields generally consider either the mean trait value or its variance. Alternatively, the keystone individual concept from behavioral ecology posits that a single individual with an extreme phenotype can have disproportionate and irreplaceable effects on group dynamics. Here, I generalize this concept to include nonbehavioral traits and broader ecological and evolutionary dynamics.

An invasive herbivore structures plant competitive dynamics.

Species interactions are central to our understanding of ecological communities, but may change rapidly with the introduction of invasive species. Invasive species can alter species interactions and community dynamics directly by having larger detrimental effects on some species than others, or indirectly by changing the ways in which native species compete among themselves. We tested the direct and indirect effects of an invasive aphid herbivore on a native aphid species and two host milkweed species.

Cannibalism by damselflies increases with rising temperature.

Trophic interactions are likely to change under climate warming. These interactions can be altered directly by changing consumption rates, or indirectly by altering growth rates and size asymmetries among individuals that in turn affect feeding. Understanding these processes is particularly important for intraspecific interactions, as direct and indirect changes may exacerbate antagonistic interactions.

Predator personality structures prey communities and trophic cascades.

Intraspecific variation is central to our understanding of evolution and population ecology, yet its consequences for community ecology are poorly understood. Animal personality - consistent individual differences in suites of behaviours - may be particularly important for trophic dynamics, where predator personality can determine activity rates and patterns of attack. We used mesocosms with aquatic food webs in which the top predator (dragonfly nymphs) varied in activity and subsequent attack rates on zooplankton, and tested the effects of predator personality.

Host-parasitoid evolution in a metacommunity.

Patch size and isolation are predicted to alter both species diversity and evolution; yet, there are few empirical examples of eco-evolutionary feedback in metacommunities. We tested three hypotheses about eco-evolutionary feedback in a gall-forming fly, Eurosta solidaginis and two of its natural enemies that select for opposite traits: (i) specialization and poor dispersal ability constrain a subset of natural enemies from occupying small and isolated patches, (ii) this constraint alters selection on the gall fly, causing phenotypic shifts towards traits resistant to generalist and dispersive enemies in small and isolated patches, and (iii) reduced dispersal evolves in small, isolated populations. We sampled patches in a natural metacommunity and found support for all hypotheses; Eurosta's specialist wasp parasitoid attacked fewer galls in small and isolated patches, generating a selection gradient that favoured small galls resistant to predation by a dispersive and generalist bird predator.