Abstract
A simulation model is used to examine the errors in estimating parasitized and nonparasitized host densities independently with Southwood's graphical technique. This technique is accurate when parasitoid attack occurs prior to the sampling period (e.g. the previous life stage of the host). When this is not the case, the parasitized host density is estimated accurately, but the unparasitized host density is over estimated by those individuals that are sampled as healthy prior to attack. This error is neglible at low levels of parasitism (<20% parasitized), but increases with increasing parasitism. Of the biological parameters tested, only the parasitoid attack pattern (shape of the parasitoid attack curve) has a significant influence on the magnitude of this error. A generalized simulation model is presented for evaluating errors in estimates of seasonal parasitism for specific host-parasitoid interactions.
Résumé
Un modèle de simulation est utilisé pour examiner les erreurs dans l'estimation des densités d'hôtes parasités et non parasités indépendamment avec la technique graphique de Southwood. Cette technique est exacte quand l'attaque du parasitoïde a lieu avant la période d'échantillonnage. Quand ceci n'est pas le cas, la densité d'hôtes parasités est estimée exactement mais la densité d'hôtes non parasités est surestimée par ces individus qui sont échantillonnés comme vivants avant l'attaque. Cette erreur est négligeable aux faibles niveaux de parasitisme (<20%), mais elle augmente avec l'accroissement du parasitisme. Des paramètres biologiques testés, seul le modèle d'attaque du parasitoïde (forme de la courbe d'attaque du parasitoïde) a une influence significative sur la valeur de cette erreur. Un modèle de simulation généralisé est présenté pour évaluer les erreurs dans l'estimation du parasitisme saisonnier pour les interactions spécifiques hôte-parasitoïde.
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University of Rhode Island, Agricultural Experiment Station Journal, Article Number 2479.
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Groden, E., Drummond, F.A., Casagrande, R.A. et al. Errors associated with estimating parasitism using a modified version of Southwood's graphical method. Entomophaga 35, 335–346 (1990). https://doi.org/10.1007/BF02375257
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DOI: https://doi.org/10.1007/BF02375257