The Experts below are selected from a list of 81 Experts worldwide ranked by ideXlab platform

Priyanga Amarasekare - One of the best experts on this subject based on the ideXlab platform.

  • Effects of temperature on Consumer-Resource Interactions.
    The Journal of animal ecology, 2015
    Co-Authors: Priyanga Amarasekare
    Abstract:

    Understanding how temperature variation influences the negative (e.g. self-limitation) and positive (e.g. saturating functional responses) feedback processes that characterize Consumer-Resource Interactions is an important research priority. Previous work on this topic has yielded conflicting outcomes with some studies predicting that warming should increase Consumer-Resource oscillations and others predicting that warming should decrease Consumer-Resource oscillations. Here, I develop a Consumer-Resource model that both synthesizes previous findings in a common framework and yields novel insights about temperature effects on Consumer-Resource dynamics. I report three key findings. First, when the resource species' birth rate exhibits a unimodal temperature response, as demonstrated by a large number of empirical studies, the temperature range over which the Consumer-Resource Interaction can persist is determined by the lower and upper temperature limits to the resource species' reproduction. This contrasts with the predictions of previous studies, which assume that the birth rate exhibits a monotonic temperature response, that consumer extinction is determined by temperature effects on consumer species' traits, rather than the resource species' traits. Secondly, the comparative analysis I have conducted shows that whether warming leads to an increase or decrease in Consumer-Resource oscillations depends on the manner in which temperature affects intraspecific competition. When the strength of self-limitation increases monotonically with temperature, warming causes a decrease in Consumer-Resource oscillations. However, if self-limitation is strongest at temperatures physiologically optimal for reproduction, a scenario previously unanalysed by theory but amply substantiated by empirical data, warming can cause an increase in Consumer-Resource oscillations. Thirdly, the model yields testable comparative predictions about Consumer-Resource dynamics under alternative hypotheses for how temperature affects competitive and resource acquisition traits. Importantly, it does so through empirically quantifiable metrics for predicting temperature effects on consumer viability and Consumer-Resource oscillations, which obviates the need for parameterizing complex dynamical models. Tests of these metrics with empirical data on a host-parasitoid Interaction yield realistic estimates of temperature limits for consumer persistence and the propensity for Consumer-Resource oscillations, highlighting their utility in predicting temperature effects, particularly warming, on Consumer-Resource Interactions in both natural and agricultural settings.

  • A metric for quantifying the oscillatory tendency of Consumer-Resource Interactions.
    The American naturalist, 2014
    Co-Authors: Chris Johnson, Priyanga Amarasekare
    Abstract:

    The oscillatory tendency of Consumer-Resource Interactions is a key determinant of food-web persistence. Here, we develop a metric for quantifying oscillatory tendency that scales the positive feedback effects of saturating functional responses with the negative feedback effects of self-limitation. We use this metric to predict the oscillatory tendency of a pairwise Interaction, tritrophic chain, and tritrophic web. This framework yields two key predictions. First, the oscillatory tendency of any food web increases with the number of trophic links with long handling times regardless of the magnitude of attack rates. Attack rates influence oscillatory tendency only when handling times are short. Second, the realized oscillatory tendency of a trophic link depends on how the product of the attack rate and handling time scales with the strength of self-limitation. Importantly, our metric allows calculations of the critical self-limitation strength at which a Consumer-Resource Interaction moves from stable to oscillatory dynamics. Our data analysis reveals that the majority (77%) of Interactions involve low attack rates and handling times, requiring only a modest level of self-limitation to suppress oscillations. Only 23% of the Interactions exhibit a strong oscillatory tendency, consistent with previous findings, based on time-series data, that 30% of Consumer-Resource Interactions in nature exhibit oscillations.

Akihiko Mougi - One of the best experts on this subject based on the ideXlab platform.

  • Population cycles emerging through multiple Interaction types.
    Royal Society open science, 2017
    Co-Authors: Naoya Mitani, Akihiko Mougi
    Abstract:

    Cyclic dynamics of populations are outstanding and widespread phenomena across many taxa. Previous theoretical studies have mainly focused on the Consumer-Resource Interaction as the driving force for such cycling. However, natural ecosystems comprise diverse types of species Interactions, but their roles in population dynamics remains unclear. Here, using a four-species hybrid module with antagonistic, mutualistic and competitive Interactions, we analytically showed that the system with major Interaction types can drive population cycles. Stronger Interactions easily cause cycling, and even when sub-modules with possible combinations of two Interactions are stabilized by weak Interactions, the system with all Interaction types can cause unstable population oscillations. Diversity of Interaction types allows to add mutualists to the list of drivers of oscillations in a focal species' population size, when they act in conjunction to other drivers.

  • Supplementary material from "Population cycles emerging through multiple Interaction types"
    2017
    Co-Authors: Naoya Mitani, Akihiko Mougi
    Abstract:

    Cyclic dynamics of populations are outstanding and widespread phenomena across many taxa. Previous theoretical studies have mainly focused on the consumer–resource Interaction as the driving force for such cycling. However, natural ecosystems comprise diverse types of species Interactions, but their roles in population dynamics remains unclear. Here, using a four-species hybrid module with antagonistic, mutualistic and competitive Interactions, we analytically showed that the system with major Interaction types can drive population cycles. Stronger Interactions easily cause cycling, and even when sub-modules with possible combinations of two Interactions are stabilized by weak Interactions, the system with all Interaction types can cause unstable population oscillations. Diversity of Interaction types allows to add mutualists to the list of drivers of oscillations in a focal species' population size, when they act in conjunction to other drivers.

Kevin S. Mccann - One of the best experts on this subject based on the ideXlab platform.

  • Daphnia inhibits the emergence of spatial pattern in a simple consumer–resource system
    Ecology, 2017
    Co-Authors: Gustavo S. Betini, Kevin S. Mccann, Tal Avgar, John M. Fryxell
    Abstract:

    Spatial self-organization can occur in many ecosystems with important effects on food web dynamics and the maintenance of biodiversity. The Consumer-Resource Interaction is known to generate spatial patterning, but only a few empirical studies have investigated the effect of the consumer on resource distribution. Here we report results from a large aquatic mesocosm experiment used to investigate the effect of the consumer Daphnia magna on the distribution of its resource, the green algae Chlorella vulgaris. We maintained large tanks with capacity for 26 ,000 L with either algae or both algae and Daphnia in different temperature conditions. We found that the presence of D. magna inhibited spatial structure in algal distribution that arose as a consequence of increasing temperature. We conjecture that this homogenization effect might be caused by a combination of high mobility combined with high rates of algal consumption by Daphnia. Our study emphasizes the importance of both local constraints on growth and behavioral responses in either promoting or suppressing spatial self-organization in natural populations.

  • The duality of stability: towards a stochastic theory of species Interactions
    Theoretical Ecology, 2016
    Co-Authors: Gabriel Gellner, Kevin S. Mccann, Alan Hastings
    Abstract:

    Understanding the dynamics of ecological systems using stability concepts has been a key driver in ecological research from the inception of the field. Despite the tremendous effort put into this area, progress has been limited due to the bewildering number of metrics used to describe ecological stability. Here, we seek to resolve some of the confusion by unfolding the dynamics of a simple Consumer-Resource Interaction module. In what follows, we first review common dynamical metrics of stability (CV, eigenvalues). We argue using the classical type II Consumer-Resource model as an example where the empirical stability metric, CV, hides two different, but important, aspects of stability: (i) stability due to mean population density processes and (ii) stability due to population density variance processes. We then employ a simple stochastic Consumer-Resource framework in order to elucidate (i) when we expect these two different aspects of stability to arise in ecological systems and, importantly, highlight (ii) the fact that these two different aspects of stability respond differentially, but predictably, to changes in fundamental parameters that govern biomass flux and loss in any Consumer-Resource Interaction (e.g., attack rates, carrying capacity, mortality).

  • Weak Interactions and Instability Cascades
    Scientific reports, 2015
    Co-Authors: Taku Kadoya, Kevin S. Mccann
    Abstract:

    Food web theory states that a weak interactor which is positioned in the food web such that it tends to deflect, or mute, energy away from a potentially oscillating Consumer-Resource Interaction often enhances community persistence and stability. Here we examine how adding other weak Interactions (predation/harvesting) on the stabilizing weak interactor alters the stability of food web using a set of well-established food web models/modules. We show that such “weak on weak” Interaction chains drive an indirect dynamic cascade that can rapidly ignite a distant Consumer-Resource oscillator. Nonetheless, we also show that the “weak on weak” Interactions are still more stable than the food web without them, and so weak Interactions still generally act to stabilize food webs. Rather, these results are best interpreted to say that the degree of the stabilizing effect of a given important weak Interaction can be severely compromised by other weak Interactions (including weak harvesting).

  • Lagged Consumer-Resource Dynamics
    Food Webs (MPB-50), 2011
    Co-Authors: Kevin S. Mccann
    Abstract:

    This chapter examines the influence of biological lags on consumer–resource dynamics, with particular emphasis on how consumer–resource cycles, or the lack thereof, interact with population level dynamical phenomena. It first considers discrete consumer–resource Interactions before discussing the dynamics of stage-structured consumer–resource Interactions. It then explains how stage structure promotes the possibility of alternative stable states and changes consumer–resource Interaction strength. It also shows how a change in population structure affects food web Interactions and/or the strengths of food webs. Finally, it reviews empirical results that show how stage structure and food web Interaction influence ecological stability. The chapter argues that weak and inherently stable consumer–resource Interactions can mute a potentially unstable population level phenomenon, and that a dynamically decoupled stable stage class can strongly stabilize other stages and the consumer–resource Interaction.

  • Consumer-Resource Dynamics: Building Consumptive Food Webs
    Food Webs (MPB-50), 2011
    Co-Authors: Kevin S. Mccann
    Abstract:

    This chapter examines the dynamics of consumer–resource Interaction, one of the fundamental building blocks of food webs. In particular, it considers how consumer–resource systems that are nonexcitable and excitable respond to changes in Interaction strength. The chapter begins with a discussion of two classes of Interaction-strength metrics: the first focuses on instantaneous rates of change in one species with respect to another species; the second follows the longer-term influence of the removal of (or change in) one species on the density of another focal species. Continuous consumer–resource models are then described, after which two underlying mechanisms that are behind the stabilization of consumer–resource Interactions are analyzed. The chapter concludes with a review of microcosm experiments and empirical data that show consistency with the proposed consumer–resource theory.

Diane S. Srivastava - One of the best experts on this subject based on the ideXlab platform.

  • biogeographic context dependence of trophic cascade strength in bromeliad food webs
    Ecology, 2019
    Co-Authors: Robin M. Lecraw, Diane S. Srivastava
    Abstract:

    Ecosystem functions and the biomass of lower trophic levels are frequently controlled by predators. The strength of top‐down control in these trophic cascades can be affected by the identity and diversity of predators, prey, and resources, as well as environmental conditions such as temperature, moisture, and nutrient loading, which can all impact Interaction strength between trophic levels. Few studies have been able to replicate a complete community over a large geographic area to compare the full trophic cascade in a manipulative experiment. Here, we identify geographic dependency in trophic cascade strength, and the driving factors and specific mechanisms behind it, by combining geographically replicated experiments with a novel approach of community analogues of common garden and transplant experiments. We studied a predator–detritivore–detritus food web in bromeliads in Puerto Rico, Costa Rica, and Brazil. We found that Interaction strengths between resources, consumers, and predators were strongly site‐specific, but the exact mechanism differed between trophic levels. Large bodied predators created strong Interaction strengths between predator and consumer trophic levels, reducing consumer abundance regardless of the geographic location, whereas small‐bodied predators created weak Interactions with no impact on consumer abundances in any site. In contrast, the Interaction strength between consumers and resources varied among sites, depending on the dominant species of leaf detritus. More labile leaf species in Costa Rica created a strong consumer–resource Interaction and therefore strong trophic cascade, whereas tougher leaf species in Brazil created a weak consumer–resource Interaction, and an overall weaker trophic cascade. Our study highlights the importance of replicating experiments over geographic scales to understand general patterns of ecological processes.

Naoya Mitani - One of the best experts on this subject based on the ideXlab platform.

  • Population cycles emerging through multiple Interaction types.
    Royal Society open science, 2017
    Co-Authors: Naoya Mitani, Akihiko Mougi
    Abstract:

    Cyclic dynamics of populations are outstanding and widespread phenomena across many taxa. Previous theoretical studies have mainly focused on the Consumer-Resource Interaction as the driving force for such cycling. However, natural ecosystems comprise diverse types of species Interactions, but their roles in population dynamics remains unclear. Here, using a four-species hybrid module with antagonistic, mutualistic and competitive Interactions, we analytically showed that the system with major Interaction types can drive population cycles. Stronger Interactions easily cause cycling, and even when sub-modules with possible combinations of two Interactions are stabilized by weak Interactions, the system with all Interaction types can cause unstable population oscillations. Diversity of Interaction types allows to add mutualists to the list of drivers of oscillations in a focal species' population size, when they act in conjunction to other drivers.

  • Supplementary material from "Population cycles emerging through multiple Interaction types"
    2017
    Co-Authors: Naoya Mitani, Akihiko Mougi
    Abstract:

    Cyclic dynamics of populations are outstanding and widespread phenomena across many taxa. Previous theoretical studies have mainly focused on the consumer–resource Interaction as the driving force for such cycling. However, natural ecosystems comprise diverse types of species Interactions, but their roles in population dynamics remains unclear. Here, using a four-species hybrid module with antagonistic, mutualistic and competitive Interactions, we analytically showed that the system with major Interaction types can drive population cycles. Stronger Interactions easily cause cycling, and even when sub-modules with possible combinations of two Interactions are stabilized by weak Interactions, the system with all Interaction types can cause unstable population oscillations. Diversity of Interaction types allows to add mutualists to the list of drivers of oscillations in a focal species' population size, when they act in conjunction to other drivers.