scholarly journals Population dynamics of multi-host communities attacked by a common parasitoid

2021 ◽  
Author(s):  
Abhyudai Singh
Keyword(s):  
Population Dynamics ◽  
Functional Response ◽  
Host Species ◽  
Attack Rate ◽  
Host Density ◽  
Apparent Competition ◽  
Species Interaction ◽  
Type I ◽  
Type Iii ◽  
Time Formalism

AbstractWe model population dynamics of two host species attacked by a common parasitoid using a discrete-time formalism that captures their population densities from year to year. It is well known starting from the seminal work of Nicholson and Bailey that a constant parasitoid attack rate leads to an unstable host-parasitoid interaction. However, a Type III functional response, where the parasitoid attack rate accelerates with increasing host density stabilizes the population dynamics. We first consider a scenario where both host species are attacked by a parasitoid with the same Type III functional response. Our results show that sufficient fast acceleration of the parasitoid attack rate stabilizes the population dynamics of all three species. For two symmetric host species, the extent of acceleration needed to stabilize the three-species equilibrium is exactly the same as that needed for a single host-parasitoid interaction. However, asymmetry can lead to scenarios where the removal of a host species from a stable interaction destabilizes the interaction between the remaining host species and the parasitoid. Next, we consider a situation where one of the host species is attacked at a constant rate (i.e., Type I functional response), and the other species is attacked via a Type III functional response. We identify parameter regimes where a Type III functional response to just one of the host species stabilizes the three species interaction. In summary, our results show that a generalist parasitoid with a Type III functional response to one or many host species can play a key role in stabilizing population dynamics of host-parasitoid communities in apparent competition.

scholarly journals Fluctuations in population densities inform stability mechanisms in host-parasitoid interactions

2021 ◽  
Author(s):  
Abhyudai Singh
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Functional Response ◽  
Discrete Time ◽  
Host Population ◽  
Reproduction Rate ◽  
Population Densities ◽  
Type Iii ◽  
Time Formalism ◽  
Large Fluctuations

AbstractPopulation dynamics of host-parasitoid interactions has been traditionally studied using a discrete-time formalism starting from the classical work of Nicholson and Bailey. It is well known that differences in parasitism risk among individual hosts can stabilize the otherwise unstable equilibrium of the Nicholson-Bailey model. Here, we consider a stochastic formulation of these discrete-time models, where the host reproduction is a random variable that varies from year to year and drives fluctuations in population densities. Interestingly, our analysis reveals that there exists an optimal level of heterogeneity in parasitism risk that minimizes the extent of fluctuations in the host population density. Intuitively, low variation in parasitism risk drives large fluctuations in the host population density as the system is on the edge of stability. In contrast, high variation in parasitism risk makes the host equilibrium sensitive to the host reproduction rate, also leading to large fluctuations in the population density. Further results show that the correlation between the adult host and parasitoid densities is high for the same year, and gradually decays to zero as one considers cross-species correlations across different years. We next consider an alternative mechanism of stabilizing host-parasitoid population dynamics based on a Type III functional response, where the parasitoid attack rate accelerates with increasing host density. Intriguingly, this nonlinear functional response makes qualitatively different correlation signatures than those seen with heterogeneity in parasitism risk. In particular, a Type III functional response leads to uncorrelated adult and parasitoid densities in the same year, but high cross-species correlation across successive years. In summary, these results argue that the cross-correlation function between population densities contains signatures for uncovering mechanisms that stabilize consumer-resource population dynamics.

scholarly journals Stochasticity in host-parasitoid models informs mechanisms regulating population dynamics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abhyudai Singh
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Functional Response ◽  
Discrete Time ◽  
Host Population ◽  
Reproduction Rate ◽  
Population Densities ◽  
Type Iii ◽  
Time Formalism ◽  
Large Fluctuations

AbstractPopulation dynamics of host-parasitoid interactions have been traditionally studied using a discrete-time formalism starting from the classical work of Nicholson and Bailey. It is well known that differences in parasitism risk among individual hosts can stabilize the otherwise unstable equilibrium of the Nicholson-Bailey model. Here, we consider a stochastic formulation of these discrete-time models, where the host reproduction is a random variable that varies from year to year and drives fluctuations in population densities. Interestingly, our analysis reveals that there exists an optimal level of heterogeneity in parasitism risk that minimizes the extent of fluctuations in the host population density. Intuitively, low variation in parasitism risk drives large fluctuations in the host population density as the system is on the edge of stability. In contrast, high variation in parasitism risk makes the host equilibrium sensitive to the host reproduction rate, also leading to large fluctuations in the population density. Further results show that the correlation between the adult host and parasitoid densities is high for the same year, and gradually decays to zero as one considers cross-species correlations across different years. We next consider an alternative mechanism of stabilizing host-parasitoid population dynamics based on a Type III functional response, where the parasitoid attack rate accelerates with increasing host density. Intriguingly, this nonlinear functional response makes qualitatively different correlation signatures than those seen with heterogeneity in parasitism risk. In particular, a Type III functional response leads to uncorrelated adult and parasitoid densities in the same year, but high cross-species correlation across successive years. In summary, these results argue that the cross-correlation function between population densities contains signatures for uncovering mechanisms that stabilize consumer-resource population dynamics.

scholarly journals Effects of buprofezin and imidacloprid on the functional response of Eretmocerus mundus Mercet

2014 ◽  
Vol 50 (No. 3) ◽  
pp. 145-150 ◽  
Author(s):  
F. Sohrabi ◽  
P. Shishehbor ◽  
M. Saber ◽  
M.S. Mosaddegh
Keyword(s):  
Functional Response ◽  
Bemisia Tabaci ◽  
Natural Enemies ◽  
Attack Rate ◽  
Sublethal Effects ◽  
Handling Time ◽  
Type Ii ◽  
Type Iii ◽  
Eretmocerus Mundus

Eretmocerus mundus Mercet is one of the key natural enemies of Bemisia tabaci (Gennadius). In this study, the sublethal effects of LC<sub>25</sub> of imidacloprid and field-recommended concentration of buprofezin on the functional response of E. mundus to different densities of second instar B. tabaci nymphs were evaluated. The results revealed a type III functional response in the control and imidacloprid treatment. The type III functional response was altered into a type II by buprofezin. Although imidacloprid did not alter the type of functional response of E. mundus compared to the control, it negatively affected the handling time and maximum attack rate of the parasitoid. Therefore, the use of this insecticide should be evaluated carefully in IPM programs.

scholarly journals Warming can destabilise predator-prey interactions by shifting the functional response from Type III to Type II

2018 ◽  
Author(s):  
Uriah Daugaard ◽  
Owen Petchey ◽  
Frank Pennekamp
Keyword(s):  
Population Dynamics ◽  
Functional Response ◽  
Conversion Efficiency ◽  
Trophic Interactions ◽  
Clearance Rate ◽  
Temperature Effects ◽  
Type Ii ◽  
Predator Prey ◽  
Type Iii ◽  
Population Dynamic Model

The potential for climate change and temperature shifts to affect community stability remains relatively unknown. One mechanism by which temperature may affect stability is by altering trophic interactions. The functional response quantifies the per capita resource consumption by the consumer as a function of resource abundance and is a suitable framework for the description of nonlinear trophic interactions. We studied the effect of temperature on a ciliate predator-prey pair (Spathidium sp. and Dexiostoma campylum) by estimating warming effects on the functional response and on the associated conversion efficiency of the predator. We recorded prey and predator dynamics over 24 hours and at three temperature levels (15, 20 and 25 C). To these data we fitted a population dynamic model including the predator functional response, such that the functional response parameters (space clearance rate, handling time, and density dependence of space clearance rate) were estimated for each temperature separately. To evaluate the ecological significance of temperature effects on the functional response parameters we simulated predator-prey population dynamics. We considered the predator-prey system to be destabilised, if the prey was driven extinct by the predator. Effects of increased temperature included a transition of the functional response from a Type III to a Type II and an increase of the conversion efficiency of the predator. The simulated population dynamics showed a destabilisation of the system with warming, with greater risk of prey extinction at higher temperatures likely caused by the transition from a Type III to a Type II functional response. Warming-induced shifts from a Type III to II are not commonly considered in modelling studies that investigate how population dynamics respond to warming. Future studies should investigate the mechanism and generality of the effect we observed and simulate temperature effects in complex food webs including shifts in the type of the functional response as well as consider the possibility of a temperature dependent conversion efficiency.

scholarly journals Global redistribution and local migration in semi-discrete host-parasitoid population dynamic models

2019 ◽  
Author(s):  
Brooks Emerick ◽  
Abhyudai Singh
Keyword(s):  
Population Dynamics ◽  
Functional Response ◽  
Dynamic Models ◽  
Constant Density ◽  
Spatial Effects ◽  
Modeling Framework ◽  
Type Iii ◽  
Stable Coexistence ◽  
Vulnerable Period ◽  
Parasitoid Population

ABSTRACTHost-parasitoid population dynamics is often probed using a semi-discrete/hybrid modeling framework. Here, the update functions in the discrete-time model connecting year-to-year changes in the population densities are obtained by solving ordinary differential equations that mechanistically describe interactions when hosts become vulnerable to parasitoid attacks. We use this semi-discrete formalism to study two key spatial effects: local movement (migration) of parasitoids between patches during the vulnerable period; and yearly redistribution of populations across patches outside the vulnerable period. Our results show that in the absence of any redistribution, constant density-independent migration and parasitoid attack rates are unable to stabilize an otherwise unstable host-parasitoid population dynamics. Interestingly, inclusion of host redistribution (but not parasitoid redistribution) before the start of the vulnerable period can lead to stable coexistence of both species. Next, we consider a Type-III functional response (parasitoid attack rate increases with host density), where the absence of any spatial effects leads to a neutrally stable host-parasitoid equilibrium. As before, density-independent parasitoid migration by itself is again insufficient to stabilize the population dynamics and host redistribution provides a stabilizing influence. Finally, we show that a Type-III functional response combined with density-dependent parasitoid migration leads to stable coexistence, even in the absence of population redistributions. In summary, we have systematically characterized parameter regimes leading to stable/unstable population dynamics with different forms of spatial heterogeneity coupled to the parasitoid’s functional response using mechanistically formulated semi-discrete models.

AN IMPROVEMENT OF THE HOLLING TYPE III FUNCTIONAL RESPONSE IN ENTOMOPHAGOUS SPECIES MODEL

2007 ◽  
Vol 15 (04) ◽  
pp. 515-524 ◽  
Author(s):  
T. CABELLO ◽  
M. GÁMEZ ◽  
Z. VARGA
Keyword(s):  
Biological Control ◽  
Functional Response ◽  
Type I ◽  
Parasitoid Species ◽  
Predator Species ◽  
Predator Prey ◽  
Type Iii ◽  
Prey System ◽  
Biological Interpretation ◽  
Chelonus Blackburni

In this study, we analyze the functional response for a parasitoid-host and a predator-prey system, as a tool of biological control of pests to evaluate the potential of bio-control agents. A possible biological interpretation was given to the adjustment coefficients of type I and II functional response by Hassell.1 Based on this, we propose new expressions for type III in terms of a new parameter that we call entomophagous potential (parasitoid or predator), providing examples using actual data from trials carried out previously for parasitoid species Chelonus blackburni Cameron (Hym.: Braconidae) and predator species Joppeicus paradoxus Puton (Het.: Joppeicidae). The novelty of the paper consists in the fact that these new expressions for Holling type III functional response have a biological interpretation, and result in a better fit to data than Hassel's model.

scholarly journals Revisiting the influence of learning in predator functional response, how it can lead to shapes different from type III.

2021 ◽  
Author(s):  
Octavio Bruzzone ◽  
María Aguirre ◽  
Jorge Hill ◽  
Eduardo Virla ◽  
Guillermo Logarzo
Keyword(s):  
Functional Response ◽  
Learning Curves ◽  
Point Of View ◽  
Type I ◽  
Alternative Prey ◽  
Sigmoid Function ◽  
Functional Responses ◽  
Type Iii ◽  
Predator Learning ◽  
Biological Taxa

Abstract Predator/Parasitoid functional response is one of the main tools used to study predation behaviour, and in assessing the potential of biological control candidates. It is generally accepted that predator learning in prey searching and manipulation can produce the appearance of type III functional response. Holling proposed that in the presence of alternative prey, at some point the predator would shift the preferred prey, leading to the appearance of a sigmoid function that characterized that functional response. This is supported by the analogy between enzyme kinetics and functional response that Holling used as the basis for developing this theory. However, after several decades, sigmoidal functional responses appear in the absence of alternative prey in most of the biological taxa studied. Here, we propose modelling the effect of learning on the functional response by using the explicit incorporation of learning curves in the parameters of the Holling functional response, the attack rate (a), and the manipulation time (h). We then study how the variation in the parameters of the learning curves causes variations in the shape of the functional response curve. We found that the functional response product of learning can be either type I, II or III, depending on what parameters act on the organism, and how much it can learn throughout the length of the study. Therefore the presence of other types of curves should not be automatically associated with the absence of learning. These results are important from an ecological point of view because when type III functional response is associated with learning, it is generally accepted that it can operate as a stabilizing factor in population dynamics. Our results, to the contrary, suggest that depending on how it acts, it may even be destabilizing by generating the appearance of functional responses close to type I.

Methionine-Specific Staining of Collagen

1982 ◽  
Vol 40 ◽  
pp. 294-295
Author(s):  
E.M. Kuhn ◽  
K.D. Marenus ◽  
M. Beer
Keyword(s):  
Amino Acids ◽  
Collagen Fibers ◽  
Type Iii Collagen ◽  
Type I ◽  
Electron Microscopic ◽  
Good Correspondence ◽  
Specific Staining ◽  
Type Iii ◽  
Different Types ◽  
Sulfur Containing

Fibers composed of different types of collagen cannot be differentiated by conventional electron microscopic stains. We are developing staining procedures aimed at identifying collagen fibers of different types.Pt(Gly-L-Met)Cl binds specifically to sulfur-containing amino acids. Different collagens have methionine (met) residues at somewhat different positions. A good correspondence has been reported between known met positions and Pt(GLM) bands in rat Type I SLS (collagen aggregates in which molecules lie adjacent to each other in exact register). We have confirmed this relationship in Type III collagen SLS (Fig. 1).

Labelling of non-A, non-B hepatitis infected chimpanzee hepatocytes with nuclease-gold conjugates

1984 ◽  
Vol 42 ◽  
pp. 250-251
Author(s):  
G. D. Gagne ◽  
M. F. Miller ◽  
D. A. Peterson
Keyword(s):  
Endoplasmic Reticulum ◽  
Experimental Infection ◽  
Uranyl Acetate ◽  
Type I ◽  
Cellular Injury ◽  
Type Ii ◽  
Tubular Structures ◽  
Type Iii ◽  
Type Iv ◽  
Infected Chimpanzee

Experimental infection of chimpanzees with non-A, non-B hepatitis (NANB) or with delta agent hepatitis results in the appearance of characteristic cytoplasmic alterations in the hepatocytes. These alterations include spongelike inclusions (Type I), attached convoluted membranes (Type II), tubular structures (Type III), and microtubular aggregates (Type IV) (Fig. 1). Type I, II and III structures are, by association, believed to be derived from endoplasmic reticulum and may be morphogenetically related. Type IV structures are generally observed free in the cytoplasm but sometimes in the vicinity of type III structures. It is not known whether these structures are somehow involved in the replication and/or assembly of the putative NANB virus or whether they are simply nonspecific responses to cellular injury. When treated with uranyl acetate, type I, II and III structures stain intensely as if they might contain nucleic acids. If these structures do correspond to intermediates in the replication of a virus, one might expect them to contain DNA or RNA and the present study was undertaken to explore this possibility.

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