scholarly journals Quantifying predator dependence in the functional response of generalist predators

2016 ◽  
Author(s):  
Mark Novak ◽  
Christopher Wolf ◽  
Kyle Coblentz ◽  
Isaac Shepard
Keyword(s):  
Method Development ◽  
Field Experiments ◽  
Empirical Evaluation ◽  
Generalist Predators ◽  
Functional Responses ◽  
Predator Species ◽  
Ratio Dependence ◽  
Species Abundances ◽  
Ratio Dependent ◽  
Predator Dependence

AbstractA longstanding debate concerns whether functional responses are best described by prey-dependent versus ratio-dependent models. Theory suggests that ratio dependence can explain many food web patterns left unexplained by simple prey-dependent models. However, for logistical reasons, ratio dependence and predator dependence more generally have seen infrequent empirical evaluation and then only so in specialist predators, which are rare in nature. Here we develop an approach to simultaneously estimate the prey-specific attack rates and predator-specific interference rates of predators interacting with arbitrary numbers of prey and predator species. We apply the approach to field surveys and two field experiments involving two intertidal whelks and their full suite of potential prey. Our study provides strong evidence for the presence of weak predator dependence that is closer to being prey dependent than ratio dependent over manipulated and natural ranges of species abundances. It also indicates how, for generalist predators, even the qualitative nature of predator dependence can be prey-specific.Author contributionsCW contributed to method development, KC and IS performed the caging experiment, and MN conceived of the study, carried out the fieldwork and analyses, and wrote the manuscript.

scholarly journals Evaluating the Impact of Two Generalist Predators on the Leafhopper Erasmoneura vulnerata Population Density

Insects ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 321
Author(s):  
Stefan Cristian Prazaru ◽  
Giulia Zanettin ◽  
Alberto Pozzebon ◽  
Paola Tirello ◽  
Francesco Toffoletto ◽  
...  
Keyword(s):  
Field Experiments ◽  
Field Studies ◽  
Generalist Predators ◽  
Predator Species ◽  
Potted Plants ◽  
Naturally Occurring ◽  
Orius Majusculus ◽  
Limited Effectiveness ◽  
Pest Outbreaks ◽  
The Impact

Outbreaks of the Nearctic leafhopper Erasmoneura vulnerata represent a threat to vinegrowers in Southern Europe, in particular in North-eastern Italy. The pest outbreaks are frequent in organic vineyards because insecticides labeled for organic viticulture show limited effectiveness towards leafhoppers. On the other hand, the naturally occurring predators and parasitoids of E. vulnerata in vineyards are often not able to keep leafhopper densities at acceptable levels for vine-growers. In this study, we evaluated the potential of two generalist, commercially available predators, Chrysoperla carnea and Orius majusculus, in suppressing E. vulnerata. Laboratory and semi-field experiments were carried out to evaluate both species’ predation capacity on E. vulnerata nymphs. The experiments were conducted on grapevine leaves inside Petri dishes (laboratory) and on potted and caged grapevines (semi-field); in both experiments, the leaves or potted plants were infested with E. vulnerata nymphs prior to predator releases. Both predator species exhibited a remarkable voracity and significantly reduced leafhopper densities in laboratory and semi-field experiments. Therefore, field studies were carried out over two growing seasons in two vineyards. We released 4 O. majusculus adults and 30 C. carnea larvae per m2 of canopy. Predator releases in vineyards reduced leafhopper densities by about 30% compared to the control plots. Results obtained in this study showed that the two predators have a potential to suppress the pest density, but more research is required to define appropriate predator–prey release ratios and release timing. Studies on intraguild interactions and competition with naturally occurring predators are also suggested.

scholarly journals Studies Aimed at Evaluating the Impact of Generalist Predators on the Leafhopper Erasmoneura vulnerata Populations

2021 ◽  
Author(s):  
Stefan Cristian Prazaru ◽  
Giulia Zanettin ◽  
Alberto Pozzebon ◽  
Paola Tirello ◽  
Francesco Toffoletto ◽  
...  
Keyword(s):  
Field Experiments ◽  
Generalist Predators ◽  
Recent Issue ◽  
Predator Species ◽  
Naturally Occurring ◽  
Orius Majusculus ◽  
Limited Effectiveness ◽  
North Eastern ◽  
Predation Capacity ◽  
The Impact

Outbreaks of the Nearctic leafhopper Erasmoneura vulnerata represent a recent issue for winegrowers in Southern Europe, in particular in North-eastern Italy. Problems are frequent in organic vineyards because insecticides labeled for organic viticulture show limited effectiveness towards leafhoppers. On the other hand, the response by naturally occurring predators and parasitoids to E. vulnerata populations in vineyards is often unable to keep leafhopper densities under levels that are acceptable for winegrowers. Here we evaluated the potential of two generalist predators, i.e., Chrysoperla carnea and Orius majusculus, in controlling E. vulnerata populations. Laboratory and semi-field experiments were carried out to evaluate both species' predation capacity on E. vulnerata nymphs. Then, predators were released in vineyards colonized by large E. vulnerata populations. Both predator species exhibited a remarkable voracity in the laboratory and significantly reduced leafhopper densities in semi-field experiments. Predator releases in vineyards reduced leafhopper densities by about 30%. Results obtained in laboratory, semi-field, and field experiments are discussed to implement these biocontrol agents' use in pest control tactics.

scholarly journals Ratio-Dependence in Predator-Prey Systems as an Edge and Basic Minimal Model of Predator Interference

2021 ◽  
Vol 9 ◽  
Author(s):  
Yuri V. Tyutyunov ◽  
Lyudmila I. Titova
Keyword(s):  
Volterra Model ◽  
Strong Impact ◽  
Natural Ecosystems ◽  
Functional Responses ◽  
Predator Prey ◽  
Ratio Dependence ◽  
Predator Interference ◽  
Trophic Function ◽  
Ratio Dependent ◽  
Predator Prey Models

The functional response (trophic function or individual ration) quantifies the average amount of prey consumed per unit of time by a single predator. Since the seminal Lotka-Volterra model, it is a key element of the predation theory. Holling has enhanced the theory by classifying prey-dependent functional responses into three types that long remained a generally accepted basis of modeling predator-prey interactions. However, contradictions between the observed dynamics of natural ecosystems and the properties of predator-prey models with Holling-type trophic functions, such as the paradox of enrichment, the paradox of biological control, and the paradoxical enrichment response mediated by trophic cascades, required further improvement of the theory. This led to the idea of the inclusion of predator interference into the trophic function. Various functional responses depending on both prey and predator densities have been suggested and compared in their performance to fit observed data. At the end of the 1980s, Arditi and Ginzburg stimulated a lively debate having a strong impact on predation theory. They proposed the concept of a spectrum of predator-dependent trophic functions, with two opposite edges being the prey-dependent and the ratio-dependent cases, and they suggested revising the theory by using the ratio-dependent edge of the spectrum as a null model of predator interference. Ratio-dependence offers the simplest way of accounting for mutual interference in predator-prey models, resolving the abovementioned contradictions between theory and natural observations. Depending on the practical needs and the availability of observations, the more detailed models can be built on this theoretical basis.

scholarly journals Can Generalist Predators Control Bemisia tabaci?

Insects ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 823
Author(s):  
Arash Kheirodin ◽  
Alvin M. Simmons ◽  
Jesusa C. Legaspi ◽  
Erin E. Grabarczyk ◽  
Michael D. Toews ◽  
...  
Keyword(s):  
Bemisia Tabaci ◽  
Natural Enemies ◽  
Cropping Systems ◽  
Review Literature ◽  
Generalist Predators ◽  
Generalist Predator ◽  
Predator Species ◽  
Molecular Gut Content Analysis ◽  
Biocontrol Potential ◽  
Substantial Control

The whitefly, Bemisia tabaci, has developed resistance to many insecticides, renewing interest in the biological control of this global pest. Generalist predators might contribute to whitefly suppression if they commonly occur in infested fields and generally complement rather than interfere with specialized natural enemies. Here, we review literature from the last 20 years, across US cropping systems, which considers the impacts of generalist predators on B. tabaci. Laboratory feeding trials and molecular gut content analysis suggest that at least 30 different generalist predator species willingly and/or regularly feed on these whiteflies. Nine of these predators appear to be particularly impactful, and a higher abundance of a few of these predator species has been shown to correlate with greater B. tabaci predation in the field. Predator species often occupy complementary feeding niches, which would be expected to strengthen biocontrol, although intraguild predation is also common and might be disruptive. Overall, our review suggests that a bio-diverse community of generalist predators commonly attacks B. tabaci, with the potential to exert substantial control in the field. The key challenge will be to develop reduced-spray plans so that generalist predators, and other more specialized natural enemies, are abundant enough that their biocontrol potential is realized.

The adaptation of generalist predators’ diet in a multi-prey context: insights from new functional responses

Ecology ◽  
2016 ◽  
Vol 97 (7) ◽  
pp. 1832-1841 ◽  
Author(s):  
Virgile Baudrot ◽  
Antoine Perasso ◽  
Clémentine Fritsch ◽  
Patrick Giraudoux ◽  
Francis Raoul
Keyword(s):  
Generalist Predators ◽  
Functional Responses

scholarly journals Ratio-dependent functional responses - tests with the zooplanktivore Mysis mixta

2001 ◽  
Vol 216 ◽  
pp. 181-189 ◽  
Author(s):  
S Hansson ◽  
BT De Stasio ◽  
E Gorokhova ◽  
MA Mohammadian
Keyword(s):  
Functional Responses ◽  
Mysis Mixta ◽  
Ratio Dependent

scholarly journals Photosynthetic resistance and resilience under drought and rewatering in maize plants

2020 ◽  
Author(s):  
Miao Qi ◽  
Xiaodi Liu ◽  
Yibo Li ◽  
He Song ◽  
Feng Zhang ◽  
...  
Keyword(s):  
Climate Change ◽  
Functional Traits ◽  
Crop Production ◽  
Field Experiments ◽  
Leaf Age ◽  
Radiative Energy ◽  
Future Climate Change ◽  
Severe Drought ◽  
Functional Responses ◽  
Precipitation Regimes

AbstractAbnormally altered precipitation patterns induced by climate change have profound global effects on crop production. However, the plant functional responses to various precipitation regimes remain unclear. Here, greenhouse and field experiments were conducted to determine how maize plant functional traits respond to drought, flooding, and rewatering. Drought and flooding hampered photosynthetic capacity, particularly when severe and/or prolonged. Most photosynthetic traits recovered after rewatering, with few compensatory responses. Rewatering often elicited high photosynthetic resilience in plants exposed to severe drought at the end of plant development, with the response strongly depending on the drought severity/duration and plant growth stage. The associations of chlorophyll concentrations with photosynthetically functional activities were stronger during post-tasselling than pre-tasselling, implying an involvement of leaf age/senescence in responses to episodic drought and subsequent rewatering. Coordinated changes in chlorophyll content, gas exchange, fluorescence parameters (PSII quantum efficiency and photochemical/non-photochemical radiative energy dissipation) possibly contributed to the enhanced drought resistance and resilience and suggested a possible regulative trade-off. These findings provide fundamental insights into how plants regulate their functional traits to deal with sporadic alterations in precipitation. Breeding and management of plants with high resistance and resilience traits could help crop production under future climate change.

scholarly journals Dynamics of a three species ratio-dependent food chain model with diffusion and double free boundaries

2020 ◽  
Vol 15 ◽  
pp. 62
Author(s):  
Dawei Zhang ◽  
Beiping Duan ◽  
Binxiang Dai
Keyword(s):  
Food Chain ◽  
Dimensional Space ◽  
Chain Model ◽  
Time Behavior ◽  
Free Boundaries ◽  
Top Predator ◽  
Predator Species ◽  
Spreading And Vanishing ◽  
Ratio Dependent ◽  
Food Chain Model

This paper focuses on the dynamics of a three species ratio-dependent food chain model with diffusion and double free boundaries in one dimensional space, in which the free boundaries represent expanding fronts of top predator species. The existence, uniqueness and estimates of the global solution are discussed firstly. Then we prove a spreading–vanishing dichotomy, specifically, the top predator species either successfully spreads to the entire space as time t goes to infinity and survives in the new environment, or fails to establish and dies out in the long run. The long time behavior of the three species and criteria for spreading and vanishing are also obtained. Besides, our simulations illustrate the impacts of initial occupying area and expanding capability on the dynamics of top predator for free boundaries.

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