### Abstract

Language | English |
---|---|

Pages | 194-204 |

Number of pages | 11 |

Journal | Journal of Animal Ecology |

Volume | 62 |

Issue number | 1 |

Publication status | Published - Jan 1993 |

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### Keywords

- probabilistic model
- parasitoids
- embedded markov chain

### Cite this

*Journal of Animal Ecology*,

*62*(1), 194-204.

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*Journal of Animal Ecology*, vol. 62, no. 1, pp. 194-204.

**A probabilistic model for the functional response of a parasitoid at the behavioural time scale.** / Casas, J.; Gurney, William; Nisbet, R.M.; Roux, O.

Research output: Contribution to journal › Article

TY - JOUR

T1 - A probabilistic model for the functional response of a parasitoid at the behavioural time scale

AU - Casas, J.

AU - Gurney, William

AU - Nisbet, R.M.

AU - Roux, O.

PY - 1993/1

Y1 - 1993/1

N2 - 1. The aim of this paper is to build a probabilistic model of the functional response of a parasitoid at the behavioural time-scale. The organism used is the eulophid Sympiesis sericeicornis Nees (Hymenoptera: Eulophidae), a polyphagous ectoparasitoid attacking the apple leaf-miner Phyllonorycter cydoniella (D. & S.) (Lepidoptera: Gracillariidae). We deal exclusively with the functional response at the level of a mined leaf and restrict our attention to the cases without superparasitism. 2. We use detailed observations of the behaviour and location of the parasitoid on a leaf to define four behavioural states: searching, hunting on a mine with an unparasitized host, ovipositing, and leaving the leaf. We describe the sequence of behavioural states visited by an embedded markov chain, which is fully determined by the one-step transition probability matrix and the initial probability distribution. 3. The key element of our model is the process of leaving the leaf. We postulate that this can occur only from the searching state, and happens either by necessity, because either available hosts or useable eggs are exhausted, or by choice. We find that the probability of leaving by choice is a monotone increasing function of the number of hosts parasitized. 4. We consider a cohort of females with initial eggload distributed according to a negative binomial distribution whose parameters we obtain from independent data. An exact multinomial test of our model on the data set from which the one-step transition probabilities are obtained gives excellent results. The domain of applicability of the model is extended by relaxing two important assumptions. We also apply the exact multinomial test to an independent data set and again obtain very good results. Sensitivity analysis demonstrates that the model is sensitive to changes in the value of only one parameter.

AB - 1. The aim of this paper is to build a probabilistic model of the functional response of a parasitoid at the behavioural time-scale. The organism used is the eulophid Sympiesis sericeicornis Nees (Hymenoptera: Eulophidae), a polyphagous ectoparasitoid attacking the apple leaf-miner Phyllonorycter cydoniella (D. & S.) (Lepidoptera: Gracillariidae). We deal exclusively with the functional response at the level of a mined leaf and restrict our attention to the cases without superparasitism. 2. We use detailed observations of the behaviour and location of the parasitoid on a leaf to define four behavioural states: searching, hunting on a mine with an unparasitized host, ovipositing, and leaving the leaf. We describe the sequence of behavioural states visited by an embedded markov chain, which is fully determined by the one-step transition probability matrix and the initial probability distribution. 3. The key element of our model is the process of leaving the leaf. We postulate that this can occur only from the searching state, and happens either by necessity, because either available hosts or useable eggs are exhausted, or by choice. We find that the probability of leaving by choice is a monotone increasing function of the number of hosts parasitized. 4. We consider a cohort of females with initial eggload distributed according to a negative binomial distribution whose parameters we obtain from independent data. An exact multinomial test of our model on the data set from which the one-step transition probabilities are obtained gives excellent results. The domain of applicability of the model is extended by relaxing two important assumptions. We also apply the exact multinomial test to an independent data set and again obtain very good results. Sensitivity analysis demonstrates that the model is sensitive to changes in the value of only one parameter.

KW - probabilistic model

KW - parasitoids

KW - embedded markov chain

UR - http://www.jstor.org/stable/5494

M3 - Article

VL - 62

SP - 194

EP - 204

JO - Journal of Animal Ecology

T2 - Journal of Animal Ecology

JF - Journal of Animal Ecology

SN - 0021-8790

IS - 1

ER -