James R Vonesh

Virginia Commonwealth University | VCU · Center for Environmental Studies

Life history theory predicts that organisms with complex life cycles should transition between life stages when the ratio of growth rate (g) to risk of mortality (l) in the current stage falls below that in the subsequent stage. Empirical support for this idea has been mixed. Implicit in both theory and empirical work is that the risk of mortality...

Top predators are known to play an important role in the assembly of communities via two mechanisms: (1) by altering the colonization (or emigration) patterns of prey through behavioral habitat selection, and (2) by altering vital rates (e.g. mortality, birth) of prey after colonization. While both these mechanisms act to determine assembly, resear...

The functional response is a critical link between consumer and resource dynamics, describing how a consumer's feeding rate varies with prey density. Functional response models often assume homogenous prey size and size-independent feeding rates. However, variation in prey size due to ontogeny and competition is ubiquitous, and predation rates are...

Predicting the combined effects of predators on shared prey has long been a focus of community ecology, yet quantitative predictions often fail. Failure to account for nonlinearity is one reason for this. Moreover, prey depletion in multiple predator effects (MPE) studies generates biased predictions in applications of common experimental and quant...

The Comparative Functional Response Approach (CFRA) was developed to provide a practical methodology by which short-term experiments can be used to forecast the longer-term impacts of a potential invading consumer. The CFRA makes inferences about potential invader impact based on comparisons of the functional responses of invader and native consume...

The Comparative Functional Response Approach (CFRA) was developed to provide a practical methodology by which short-term experiments can be used to forecast the longer-term impacts of a potential invading consumer. The CFRA makes inferences about potential invader impact based on comparisons of the functional responses of invader and native consume...

The North American rock pool mosquito, Aedes atropalpus, has reportedly decreased in abundance following the introduction of Ae. japonicus japonicus to the USA, but the specific mechanisms responsible for the reduction remain unclear. Thus, there is a need for field studies to improve our knowledge of natural rock pool systems where both species co...

Warming can impact consumer–resource interactions through multiple mechanisms. For example, warming can both alter the rate at which predators consume prey and the rate prey develop through vulnerable life stages. Thus, the overall effect of warming on consumer–resource interactions will depend upon the strength and asymmetry of warming effects on...

The native rock pool mosquito, Aedes atropalpus (Coquillett), and the invasive Aedes japonicus (Theobald) have been found in many types of artificial and natural containers throughout North America. Little is known about the ecology of these two species in habitats where they co‐occur, although multiple investigators have reported the decline of th...

To effectively manage landscapes that support species with complex life cycles, managers should consider how current practices affect habitats these organisms rely on in each life stage. Prescribed fire is a landscape level disturbance that may alter both aquatic and terrestrial habitat characteristics. However, our knowledge of the effects of fire...

Predators are not limited to prey from other species as they can cannibalise vulnerable individuals within their own population. The African clawed frog, Xenopus laevis (Daudin), is a predator with a broad diet, known to consume multiple prey species, including congeners and conspecifics. African clawed frogs occur in sympatry with the Endangered C...

Understanding the factors that shape the timing of life-history switch points (SPs, e.g. hatching, metamorphosis and maturation) is a fundamental question in evolutionary ecology. Previous studies examining this question from a fitness optimization perspective have advanced our understanding of why the timing of life-history transitions may vary ac...

Predators can play an important role in regulating prey abundance and diversity, determining food web structure and function, and contributing to important ecosystem services, including the regulation of agricultural pests and disease vectors. Thus, the ability to predict predator impact on prey is an important goal in ecology. Often, predators of...

Functional response data for Xenopus laevis of different size Columns describe 1. Predator size. 2. The density of prey used. 3. The total number of prey that survived after the experiment was completed. 4. The total number of prey eaten over the duration of the entire experiment.

Predators can directly or indirectly shape food webs through a combination of consumptive and non‐consumptive effects. Yet, how these effects vary across natural populations and their consequences for adjacent ecosystems remains poorly resolved. We examined links between terrestrial predators and aquatic ecosystems through their effects on a locall...

For organisms with complex life cycles, conditions experienced during early life stages may constrain later growth and survival. Conversely, compensatory mechanisms may attenuate negative effects from early life stages. We used the spotted salamander, Ambystoma maculatum, to test how aquatic larval density and terrestrial moisture influence juvenil...

Predators can play an important role in regulating prey abundance and diversity, determining food web structure and function, and contributing to important ecosystem services, including the regulation of agricultural pests and disease vectors. Thus, the ability to predict predator impact on prey is an important goal in ecology. Often predators of t...

Predators can play an important role in regulating prey abundance and diversity, determining food web structure and function, and contributing to important ecosystem services, including the regulation of agricultural pests and disease vectors. Thus, the ability to predict predator impact on prey is an important goal in ecology. Often predators of t...

Terrestrial eggs have evolved repeatedly in tropical anurans exposing embryos to the new threat of dehydration. Red-eyed treefrogs, Agalychnis callidryas, lay eggs on plants over water. Maternally provided water allows shaded eggs in humid sites to develop to hatching without rainfall, but unshaded eggs and those in less humid sites can die from de...

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Dick et al. (Biol Invasions, 2017) propose that the comparative functional response framework provides a unifying approach for the study of invasive species. We agree that functional responses are an important and powerful quantitative description of consumer effects on resources, and co-opting classical ecological theory to better predict invasive...

No abstract

[ Biol. Lett. 12 , 20160580. (Published online 21 December 2016) ([doi:10.1098/rsbl.2016.0580][2])][2] The penultimate sentence in the Results section contains an error. The sentence ‘ … declined 44%, 48% and 51% in the predator-free control … ’ should instead read ‘ … declined 44%, 48

Changes in predator diversity via extinction and invasion are increasingly widespread and can have important ecological and socio-economic consequences. Anticipating and managing these consequences requires understanding how predators shape ecological communities. Previous predator biodiversity research has focused on post-colonization processes. H...

Aim Understanding the scales over which land use affects animal populations is critical for conservation planning, and it can provide information about the mechanisms that underlie correlations between species distributions and land use. We used a citizen science database of anuran surveys to examine the relationship between road density, land use...

Mosquito egg traps, aquatic habitats baited with oviposition attractant and insecticide, are important tools for surveillance and control efforts in integrated vector management programs. The bioinsecticide Bacillus thuringiensis subsp. israelensis (Bti) is increasingly used as an environmentally friendly alternative to chemical insecticides and th...

Variation in predation risk plays an important role in shaping prey behavior, morphology, life history, population dynamics, and community structure in freshwater systems. Anuran larvae are important prey in freshwater communities and spatiotemporal variation in risk can arise from changes in the number and identity of predators; however, our under...

Changes in predator diversity via extinction and invasion are increasingly widespread and can have important ecological and socio-economic consequences. Anticipating and managing these consequences requires understanding how predators shape ecological communities. Previous predator biodiversity research has focused on post-colonization processes. H...

Many animals with complex life cycles can cope with environmental uncertainty by altering the timing of life history switch points through plasticity. Pond hydroperiod has important consequences for the fitness of aquatic organisms and many taxa alter the timing of life history switch points in response to habitat desiccation. For example, larval a...

To adaptively express inducible defenses, prey must gauge risk based on indirect cues of predation. However, the information contained in indirect cues that enable prey to fine-tune their phenotypes to variation in risk is still unclear. In aquatic systems, research has focused on cue concentration as the key variable driving threat-sensitive respo...

Background/Question/Methods Theory predicts that organisms with complex life cycles should minimize the ratio of growth rate (g) to risk of mortality (µ) when transitioning between life stages. However, the majority of studies have found no effect of predators on timing of or size at metamorphosis. Two things may contribute to this discrepancy. F...

Background/Question/Methods For organisms with complex life cycles, plastic responses to environmental variation in early life stages may have consequences for performance in subsequent life stages. In aquatic systems, variation in intraspecific density dependence and hydroperiod can have dramatic effects on the timing of metamorphosis and post-m...

Aim We map estimated historical population declines resulting from species‐specific models of sensitivity to habitat fragmentation for three forest‐dependent chameleons. Location East Usambara Mountains, Eastern Arc Mountains, Tanzania. Methods We surveyed three chameleon species ( Rhampholeon spinosus , Rhampholeon temporalis and Trioceros derem...

Many prey species face trade-offs in the timing of life history switch points like hatching and metamorphosis. Costs associated with transitioning early depend on the biotic and abiotic conditions found in the subsequent life stage. The red-eyed treefrog, Agalychnis callidryas, faces risks from predators in multiple, successive life stages, and can...

Background/Question/Methods Habitat loss and fragmentation represent significant threats to amphibians. Fragmentation is particularly harmful because many amphibians migrate between aquatic and terrestrial habitats, and even narrow bands of unsuitable habitat can act as barriers to movement. Additionally, amphibians are slow-moving and prone to r...

Background/Question/Methods Despite general appreciation for the importance of predators in ecosystems and recognition of global changes in predator species richness, we lack a general framework for predicting how compositional changes in predator communities influence prey populations. Current statistical models for predicting the relationship be...

Most animals metamorphose, changing morphology, physiology, behavior and ecological interactions. Size- and habitat-dependent mortality risk is thought to affect the evolution and plastic expression of metamorphic timing, and high predation during the morphological transition is posited as a critical selective force shaping complex life cycles. Non...

Herbivores can both consume and facilitate primary producers with important consequences for community structure. How differences in herbivore foraging ecology alter the relative importance of such effects is not well understood, especially in tropical lentic systems. To address this issue, we manipulated the density of two herbivores with differen...

The non-consumptive effects of predators on prey can affect prey phenotypes, potentially having important consequences for communities due to trait-mediated indirect interactions. Predicting non-consumptive effects and their impacts on communities can be difficult because predators can affect resources directly through nutrient cycling and indirect...

Environmentally cued plasticity in hatching timing is widespread in animals. As with later life-history switch points, plasticity in hatching timing may have carryover effects that affect subsequent interactions with predators and competitors. Moreover, the strength of such effects of hatching plasticity may be context dependent. We used red-eyed t...

In animals with complex life cycles, fitness trade-offs across life stages determine the optimal time for transitions between stages. If these trade-offs vary predictably, adaptive plasticity in the timing of life history transitions may evolve. For instance, embryos of many species are capable of accelerating hatching to escape from egg predation...

Community ecology aims to understand how species interactions shape species diversity and abundance. Although less studied than predatory or competitive interactions, facilitative interactions can be important in communities associated with ephemeral microhabitats. Successful recruitment from these habitats requires species to rapidly colonize, dev...

To effectively balance investment in predator defenses versus other traits, organisms must accurately assess predation risk. Chemical cues caused by predation events are indicators of risk for prey in a wide variety of systems, but the relationship between how prey perceive risk in relation to the amount of prey consumed by predators is poorly unde...

Background/Question/Methods The ability of predators to alter the size structure of prey populations via consumption is well documented and can have important consequences for population and community dynamics. Predators can also alter prey size via non-consumptive mechanisms. Prey often experience reduced growth in response to indirect cues of r...

Background/Question/Methods Phenotypic plasticity allows organisms to respond to environmental change and persist in unpredictable environments. Hydroperiod is a critical driver of the ecology of aquatic habitats. Understanding how organisms respond to variation in hydroperiod is especially critical since climate change is expected to alter tempe...

Background/Question/Methods Habitat modification in the form of fragmentation and loss is a leading cause of biodiversity decline. The basic predictions from island biogeography theory that species richness and population size decrease with declining area and increased isolation have received considerable support. However much of this research ha...

Background/Question/Methods The quality and quantity of resource inputs from terrestrial habitats to aquatic habitats is important for structuring aquatic communities. Water-filled tree holes contain obligate and preferential residents highly affected by leaf litter input. Considering the loss of tree diversity and replacement of native species w...

Defensive modifications in prey traits that reduce predation risk can also have negative effects on prey fitness. Such nonconsumptive effects (NCEs) of predators are common, often quite strong, and can even dominate the net effect of predators. We develop an intuitive graphical model to identify and explore the conditions promoting strong NCEs. The...

Spatial contagion occurs when the perceived suitability of neighbouring habitat patches is not independent. As a result, organisms may colonize less-preferred patches near preferred patches and avoid preferred patches near non-preferred patches. Spatial contagion may thus alter colonization dynamics as well as the type and frequency of post-coloniz...

Adult aquatic insects are a common resource for many terrestrial predators, often considered to subsidize terrestrial food webs. However, larval aquatic insects themselves consume both aquatic primary producers and allochthonous terrestrial detritus, suggesting that adults could provide aquatic subsidy and/or recycled terrestrial energy to terrestr...

Individual and relative body size are key determinants of ecological performance, shaping the strength and types of interactions within and among species. Size-dependent performance is particularly important for iteroparous species with overlapping cohorts, determining the ability of new cohorts to invade habitats with older, larger conspecifics. W...

Metamorphosis dramatically changes morphology, physiology, behavior and performance. As anurans change from aquatic tadpoles to terrestrial juveniles, they pass through a period of poor locomotor performance and high predation risk, and individuals behaviorally determine when they shift habitats. Red-eyed treefrogs, Agalychnis callidryas, alter whe...

Harvesting of chameleons from the East Usambara Mountains of Tanzania for the exotic pet trade is of concern due to the high rates of habitat loss in this region and the fact that many of the species are endemic or near endemic to this isolated montane forest. Export of the majority of chameleons found in the East Usambaras is regulated by their li...

At last, a book that will allow you to identify most of the amphibians found in the world famous biodiversity hotspots of the Eastern Arc Mountains and Coastal Forests of Tanzania and Kenya. This guide allows both the English and the Swahili reader to identify and obtain natural history and conservation information for the 122 species of amphibians...

Background/Question/Methods The nonlethal effects of predators on prey phenotype and performance can propagate through foodwebs to affect the outcome of predator-prey interactions (trait mediated interactions; TMIs). To produce effective defensive phenotypes requires environmental cues that indicate both presence of predators and the level of ris...

Background/Question/Methods Prey frequently alter their phenotype in response to perceived predation risk in order to reduce vulnerability. Differences in the costs and benefits of such plastic responses to predators can lead to differences in non-consumptive predator effects. Such differences can occur between taxa or through ontogeny for a give...

Background/Question/Methods Organisms often exhibit strong habitat preferences, but the relative importance of habitat preference for predicting species’ distributions can be strongly dependent upon the spatial configuration of patches in the landscape. Patch clustering can lead to increased colonization of both preferred and non-preferred patche...

1. Cross-ecosystem movements of resources, including detritus, nutrients and living prey, can strongly influence food web dynamics in recipient habitats. Variation in resource inputs is thought to be driven by factors external to the recipient habitat (e.g. donor habitat productivity and boundary conditions). However, inputs of or by ‘active’ livin...

Experimental studies in temperate regions have revealed that competition and predation interact to shape aquatic communities. Predators typically reduce the effect of competition on growth and competitors provide alternative prey subjects, which may also alter predation. Here, we examine the independent and combined effects of competition and preda...

The global resurgence and emergence of new mosquito-borne diseases and increasing resistance of mosquitoes to chemical pesticides have prompted renewed interest in biocontrol methods that use aquatic predators of mos-quito larvae. For disease vectors with complex life cycles, like mosquitoes, in which adults are terrestrial and choose aquatic habit...

Life history theory and empirical studies suggest that large size or earlier metamorphosis are suitable proxies for increased lifetime fitness. Thus, across a gradient of larval habitat quality, individuals with similar phenotypes for these traits should exhibit similar post-metamorphic performance. Here we examine this paradigm by testing for diff...

Predators can have remote effects on prey populations that are connected by migration (i.e. prey metapopulations) because predator-mediated changes in prey behavior and abundance effectively transmit the impact of predators into predator-free prey populations. Behavioral changes in prey that might give rise to remote effects are altered rates of mi...

Background/Question/Methods Resource subsidies can strongly affect food web structure and dynamics. Along with habitat shape and boundary permeability, relative productivities of donor and recipient habitats have been suggested to influence when and where subsidies are important. Yet, empirical support for this spatial framework is lacking. We sug...

Background/Question/Methods Most animals undergo substantial changes in body size and morphology during ontogeny. Body size determines many aspects of ecological performance, including foraging rate, fecundity, range size and predation risk. Size structure in prey populations can strongly influence predator-prey interactions, and prey size select...

Background/Question/Methods Most species have complex life cycles in which they are vulnerable to different suites of predators as they shift habitats through ontogeny. While these predators, separated in time and space, do not interact directly, they may still interact indirectly via their effects on the density and traits of their shared prey. F...

Background/Question/Methods As organisms with complex life cycles transition between life-stages, trade-offs in risks and opportunities focus selection from two sequential, potentially variable environments. Plasticity in the timing of life history switch points, such as hatching and metamorphosis, is phylogenetically widespread and allows organi...

Background/Question/Methods The assembly of communities can be shaped pre-colonization by processes like habitat selection as well as post-colonization by processes such as species interactions. The relative importance of processes operating at these two scales for communities that inhabit ephemeral, patchy microhabitats are poorly understood and...