scholarly journals Nonlinear functional responses and ecological pleiotropy alter the strength of disruptive selection in consumers

2018 ◽  
Author(s):  
Kyle E. Coblentz
Keyword(s):  
Functional Response ◽  
Intraspecific Competition ◽  
Ecological Effects ◽  
Disruptive Selection ◽  
Feeding Rates ◽  
Functional Responses ◽  
Resource Model ◽  
Ecological Opportunity ◽  
Nonlinear Functional ◽  
Consumer Dependence

AbstractMuch of the theory on disruptive selection has focused on selection in generalist consumers caused by ecological opportunity through the availability of alternative resources and intraspecific competition for those resources. This theory, however, makes several ecologically unrealistic assumptions. First, this theory assumes that consumers have a linear, resource-dependent functional response, ignoring well-documented effects of resource handling times and consumer dependence. Second, this theory assumes that the trait under selection only influences the percapita attack rates of the consumer, ignoring other effects of the trait that may influence feeding rates and hence fitness. Here, I develop a one consumer-two resource model to investigate how nonlinear functional responses and ecological pleiotropy (traits that have multiple simultaneous ecological effects) influence the strength of disruptive selection. I find that handling times and interference among consumers are capable of altering disruptive selection by changing feeding rates differentially across consumer phenotypes. In particular, handling times cause a decrease in the strength of disruptive selection while the effects of interference depend on the mechanism through which interference occurs. The effects of handling times and interference, however, are dependent on whether and how ecological pleiotropy causes correlations between handling times or interference rates and attack rates. Overall, my results suggest that features defining the functional responses of consumers and the relationships among those features determine the likelihood and strength of disruptive selection. In particular, disruptive selection should be strongest in generalist populations composed of individual diet specialists who experience lower handling times and interference rates on the resources for which their attack rates are highest.

scholarly journals Permanence of Periodic Predator-Prey System with General Nonlinear Functional Response and Stage Structure for Both Predator and Prey

2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
Xuming Huang ◽  
Xiangzeng Kong ◽  
Wensheng Yang
Keyword(s):  
Functional Response ◽  
Prey Species ◽  
Stage Structure ◽  
Functional Responses ◽  
Nonlinear Functional ◽  
Predator Prey ◽  
Prey System

We study the permanence of periodic predator-prey system with general nonlinear functional responses and stage structure for both predator and prey and obtain that the predator and the prey species are permanent.

scholarly journals Pushing the switch: functional responses and prey switching by invasive lionfish may mediate their ecological impact

2021 ◽  
Author(s):  
Monica McCard ◽  
Josie South ◽  
Ross N. Cuthbert ◽  
James W. E. Dickey ◽  
Nathan McCard ◽  
...  
Keyword(s):  
Functional Response ◽  
Prey Species ◽  
Effective Means ◽  
Ecological Impact ◽  
Artemia Salina ◽  
Ecological Impacts ◽  
Feeding Rates ◽  
Functional Responses ◽  
Prey Switching ◽  
Frequency Dependent

AbstractBiodiversity is declining on a global scale and the spread of invasive alien species (IAS) is a major driver, particularly through predatory impacts. Thus, effective means of assessing and predicting the consequences of IAS predation on native prey population stability remains a vital goal for conservation. Here, we applied two classic ecological concepts, consumer functional response (FR) and prey switching, to predict and understand the ecological impacts of juveniles of the lionfish (Pterois volitans), a notorious and widespread marine invader. Functional responses and prey switching propensities were quantified towards three representative prey species: Artemia salina, Palaemonetes varians, and Gammarus oceanicus. Lionfish exhibited potentially destabilising Type II FRs towards individual prey species, owing to high consumption rates at low prey densities, whilst FR magnitudes differed among prey species. Functional response attack rates (a) were highest, and handling times (h) lowest, towards A. salina, followed by P. varians and then G. oceanicus. Maximum feeding rates (1/h) and functional response ratios (FRR; a/h) also followed this impact gradient for the three prey species. Lionfish, however, displayed a potentially population stabilising prey switching propensity (i.e. frequency-dependent predation) when multiple prey species were presented simultaneously, where disproportionately less of rare prey, and more of abundant prey, were consumed. Whilst FR and FRR magnitudes indicate marked per capita lionfish predatory impacts towards prey species, a strong prey switching propensity may reduce in-field impacts by offering low density prey refuge in biodiverse communities. Our results thus corroborate field patterns documenting variable impacts of lionfish, with prey extirpations less likely in diverse communities owing to frequency-dependent predation.

scholarly journals Hidden layers of density dependence in consumer feeding rates

2020 ◽  
Author(s):  
Daniel B. Stouffer ◽  
Mark Novak
Keyword(s):  
Density Dependence ◽  
Functional Response ◽  
Species Interactions ◽  
Feeding Rates ◽  
Functional Responses ◽  
Response Models ◽  
Multiple Resources ◽  
Functional Response Models ◽  
Biotic Environment ◽  
Insight Into

AbstractFunctional responses relate a consumer’s feeding rates to variation in its abiotic and biotic environment, providing insight into consumer behavior and fitness, and underpinning population and food-web dynamics. Despite their broad relevance and long-standing history, we show here that the types of density dependence found in classic resource- and consumer-dependent functional-response models equate to strong and often untenable assumptions about the independence of processes underlying feeding rates. We first demonstrate mathematically how to quantify non-independence between feeding and consumer interference and between feeding on multiple resources. We then analyze two large collections of functional-response datasets to show that non-independence is pervasive and borne out in previously-hidden forms of density dependence. Our results provide a new lens through which to view variation in consumer feeding rates and disentangle the biological underpinnings of species interactions in multi-species contexts.

scholarly journals Systematic bias in studies of consumer functional responses

2020 ◽  
Author(s):  
Mark Novak ◽  
Daniel B. Stouffer
Keyword(s):  
Functional Response ◽  
Nonlinear Models ◽  
Systematic Bias ◽  
Functional Responses ◽  
Response Models ◽  
Point Estimates ◽  
Resource Interactions ◽  
Functional Response Models ◽  
Consumer Dependence ◽  
Insight Into

AbstractFunctional responses are a cornerstone to our understanding of consumer-resource interactions, so how to best describe them using models has been actively debated. Here we focus on the consumer dependence of functional responses to evidence systematic bias in the statistical comparison of functional-response models and the estimation of their parameters. Both forms of bias are universal to nonlinear models (irrespective of consumer dependence) and are rooted in a lack of sufficient replication. Using a large compilation of published datasets, we show that – due to the prevalence of low sample size studies – neither the overall frequency by which alternative models achieve top rank nor the frequency distribution of parameter point estimates should be treated as providing insight into the general form or central tendency of consumer interference. We call for renewed clarity in the varied purposes that motivate the study of functional responses, purposes that can compete with each other in dictating the design, analysis, and interpretation of functional-response experiments.

scholarly journals Functional Response and Intraspecific Competition in the Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

Insects ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 806
Author(s):  
Qilin Ren ◽  
Muhammad Haseeb ◽  
Jingyu Fan ◽  
Pengxiang Wu ◽  
Tianqi Tian ◽  
...  
Keyword(s):  
Pest Management ◽  
Functional Response ◽  
Intraspecific Competition ◽  
Management Strategies ◽  
Fall Armyworm ◽  
Handling Time ◽  
Search Rate ◽  
Functional Responses ◽  
Practical Applications ◽  
Larval Stages

Functional responses of the fall armyworm (FAW) larvae at each stage, and their intraspecific competition associated with cannibalism, provide insights into developing pest management strategies for the FAW. To help use insecticides more sparingly, the functional response and intraspecific competition of the FAW larvae were evaluated under the laboratory conditions. The results showed that all stages of the FAW larvae displayed a type II functional response to diet. Based on Holling’s disc equation, the search rate (a) and handling time (Th) of sixth instar larvae (a = 0.493; Th = 0.37 min) were the highest, and the shortest of all larval stages, respectively. Intraspecific competition curves fitted the data for fourth to sixth larval stages of the FAW, and the coefficient of intraspecific competition (m) assessed by the intraspecific competition equation were highest for fifth instar larvae (m = 0.48). The present study indicates that 5th and 6th instar larvae can cause the most plant damage (accounted for 88.9% of larval consumption), and these stages should be the focus of any pest management strategy. Intraspecific competition, especially cannibalism, impacts the feeding patterns of the FAW larvae and needs close attention. Understanding the functional response and intraspecific competition of the FAW larvae contributes greatly to practical applications of insecticides, increasing the effectiveness of chemical sprays and decreasing ecological damage.

scholarly journals Impacts of non-native fishes under a seasonal temperature gradient are forecasted using functional responses and abundances

NeoBiota ◽  
2019 ◽  
Vol 49 ◽  
pp. 57-75 ◽  
Author(s):  
Lubabalo Mofu ◽  
Ross N. Cuthbert ◽  
Tatenda Dalu ◽  
Darragh J. Woodford ◽  
Ryan J. Wasserman ◽  
...  
Keyword(s):  
Functional Response ◽  
Fish Species ◽  
Ecological Impacts ◽  
Seasonal Temperature ◽  
Relative Impact ◽  
Feeding Rates ◽  
Functional Responses ◽  
Mozambique Tilapia ◽  
Western Mosquitofish ◽  
Native Fishes

Developing predictive methods to forecast the impacts of existing and emerging invasive species is of critical importance to biodiversity conservation. However, invader impacts are context-dependent, making reliable and robust predictions challenging. In particular, it is unclear how temporal variabilities in relation to temperature regime shifts influence invader ecological impacts. In the present study, we quantify the functional responses of three coexisting freshwater fishes: the native freshwater River Goby Glossogobiuscallidus, and the non-native Mozambique Tilapia Oreochromismossambicus and Western Mosquitofish Gambusiaaffinis, under two temperature treatments using chironomid larvae as prey. This was used along with fish abundance data to determine temporal differences in ecological impacts of each fish species between seasons (i.e. at two corresponding temperatures). All three fish species exhibited potentially population-destabilizing Type II functional responses. Their maximum feeding rates were consistently higher in the warm temperature treatment, whereas attack rates tended to be reduced. Non-native Mozambique Tilapia had the highest maximum feeding rate under both temperature treatments (18 °C and 25 °C), followed by the non-native Western Mosquitofish and lastly the native River Goby, suggesting greater per capita impacts on native prey by non-native fishes. The predatory fish abundances differed significantly according to season, with native River Goby and non-native Mozambique Tilapia generally more abundant than non-native Western Mosquitofish. By multiplying functional response maximum feeding rates with abundances of each fish species across the seasonal gradient, the relative impact potential of non-native Mozambique Tilapia was consistently higher compared to that of native gobies. Western Mosquitofish impacts were less apparent, owing to their low abundances. We demonstrate how seasonal temperature fluctuations affect the relative impact capacities of introduced species and the utility of consumer functional response and the relative impact potential metric in impact forecasting.

scholarly journals Functional responses of a cosmopolitan invader demonstrate intraspecific variability in consumer-resource dynamics

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5634 ◽  
Author(s):  
Brett R. Howard ◽  
Daniel Barrios-O’Neill ◽  
Mhairi E. Alexander ◽  
Jaimie T.A. Dick ◽  
Thomas W. Therriault ◽  
...  
Keyword(s):  
South Africa ◽  
Northern Ireland ◽  
Functional Response ◽  
Ecological Impacts ◽  
Green Crab ◽  
Response Analysis ◽  
Feeding Rates ◽  
Functional Responses ◽  
Resource Dynamics ◽  
Consumer Resource

Background Variability in the ecological impacts of invasive species across their geographical ranges may decrease the accuracy of risk assessments. Comparative functional response analysis can be used to estimate invasive consumer-resource dynamics, explain impact variability, and thus potentially inform impact predictions. The European green crab (Carcinus maenas) has been introduced on multiple continents beyond its native range, although its ecological impacts appear to vary among populations and regions. Our aim was to test whether consumer-resource dynamics under standardized conditions are similarly variable across the current geographic distribution of green crab, and to identify correlated morphological features. Methods Crabs were collected from multiple populations within both native (Northern Ireland) and invasive regions (South Africa and Canada). Their functional responses to local mussels (Mytilus spp.) were tested. Attack rates and handling times were compared among green crab populations within each region, and among regions (Pacific Canada, Atlantic Canada, South Africa, and Northern Ireland). The effect of predator and prey morphology on prey consumption was investigated. Results Across regions, green crabs consumed prey according to a Type II (hyperbolic) functional response curve. Attack rates (i.e., the rate at which a predator finds and attacks prey), handling times and maximum feeding rates differed among regions. There was a trend toward higher attack rates in invasive than in native populations. Green crabs from Canada had lower handling times and thus higher maximum feeding rates than those from South Africa and Northern Ireland. Canadian and Northern Ireland crabs had significantly larger claws than South African crabs. Claw size was a more important predictor of the proportion of mussels killed than prey shell strength. Discussion The differences in functional response between regions reflect observed impacts of green crabs in the wild. This suggests that an understanding of consumer–resource dynamics (e.g., the per capita measure of predation), derived from simple, standardized experiments, might yield useful predictions of invader impacts across geographical ranges.

scholarly journals Functional response of Harmonia axyridis preying on Acyrthosiphon pisum nymphs: the effect of temperature

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yasir Islam ◽  
Farhan Mahmood Shah ◽  
Xu Rubing ◽  
Muhammad Razaq ◽  
Miao Yabo ◽  
...  
Keyword(s):  
Functional Response ◽  
High Performance ◽  
Acyrthosiphon Pisum ◽  
Harmonia Axyridis ◽  
Effect Of Temperature ◽  
Functional Responses ◽  
Aphid Control ◽  
Host Aphid ◽  
Predator Foraging

AbstractIn the current study, we investigated the functional response of Harmonia axyridis adults and larvae foraging on Acyrthosiphon pisum nymphs at temperatures between 15 and 35 °C. Logistic regression and Roger’s random predator models were employed to determine the type and parameters of the functional response. Harmonia axyridis larvae and adults exhibited Type II functional responses to A. pisum, and warming increased both the predation activity and host aphid control mortality. Female and 4th instar H. axyridis consumed the most aphids. For fourth instar larvae and female H. axyridis adults, the successful attack rates were 0.23 ± 0.014 h−1 and 0.25 ± 0.015 h−1; the handling times were 0.13 ± 0.005 h and 0.16 ± 0.004 h; and the estimated maximum predation rates were 181.28 ± 14.54 and 153.85 ± 4.06, respectively. These findings accentuate the high performance of 4th instar and female H. axyridis and the role of temperature in their efficiency. Further, we discussed such temperature-driven shifts in predation and prey mortality concerning prey-predator foraging interactions towards biological control.

scholarly journals Applying predator-prey theory to modelling immune-mediated, within-host interspecific parasite interactions

Parasitology ◽  
2010 ◽  
Vol 137 (6) ◽  
pp. 1027-1038 ◽  
Author(s):  
ANDY FENTON ◽  
SARAH E. PERKINS
Keyword(s):  
Functional Response ◽  
Interspecific Interactions ◽  
Parasite Load ◽  
Multiple Infections ◽  
Functional Responses ◽  
Predator Prey ◽  
Immune Activity ◽  
Parasite Communities ◽  
Immune Mediated ◽  
Predator Prey Models

SUMMARYPredator-prey models are often applied to the interactions between host immunity and parasite growth. A key component of these models is the immune system's functional response, the relationship between immune activity and parasite load. Typically, models assume a simple, linear functional response. However, based on the mechanistic interactions between parasites and immunity we argue that alternative forms are more likely, resulting in very different predictions, ranging from parasite exclusion to chronic infection. By extending this framework to consider multiple infections we show that combinations of parasites eliciting different functional responses greatly affect community stability. Indeed, some parasites may stabilize other species that would be unstable if infecting alone. Therefore hosts' immune systems may have adapted to tolerate certain parasites, rather than clear them and risk erratic parasite dynamics. We urge for more detailed empirical information relating immune activity to parasite load to enable better predictions of the dynamic consequences of immune-mediated interspecific interactions within parasite communities.

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