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ABSTRACT: Pest suppression is an important ecosystem service provided by biodiversity, though antagonistic interactions may jeopardize its impact on pest suppression. Hyperparasitoids may release herbivore populations from natural enemy pressure and lead to outbreaks directly due to parasitism as well as indirect through behavioural interference. In a previous study we reported that in native populations of Euproctis chrysorrhoea L. (Lymantriidae) primary parasitism was very low and outbreaks were more likely in coastal habitats than inland. Here we hypothesise that hyperparasitoids are the underlying cause of such patterns by reporting data on direct hyperparasitism rates as well as seasonal patterns of parasitoid attack. Of the 17 primary parasitoids attacking E. chrysorrhoea, three were found to be hyperparasitized. Hyperparasitoids attack the most important E. chrysorrhoea primary parasitoids which may explain the pattern of moth density in some habitats. Seasonal patterns of parasitoids attack and flight also help to understand antagonistic interactions among E. chrysorrhoea parasitoids. We discuss the implications of our work in the context of pest control in diverse ecosystems. (C) 2011 Elsevier Inc. All rights reserved.
Biological Control 02/2012; 60(2):123-131. · 2.00 Impact Factor
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ABSTRACT: 1. Life table studies have been an essential tool for the comprehension of insect population dynamics, although their use has been methodologically biased by a primary focus on mortality factors, especially natural enemies. Thus, studies in natural populations may relegate important mortality sources to the ‘unknown’ or ‘residual’ mortality categories. To overcome this limitation, life tables may be complemented by combining them with other approaches.2. The aim of the present study was to provide insights into browntail moth Euproctis chrysorrhoea L. (Lepidoptera: Lymantriidae) local outbreaks by combining life table data and statistical modelling. First, E. chrysorrhoea population density, mortality dynamics, net reproductive rate, and reproductive potential were compared in two different Mediterranean habitats (i.e. coastal and inland). Second, we investigated the relationship of reproductive potential as well as residual mortality (i.e. not associated to any specific mortality agent) with several variables likely to play an important role in E. chrysorrhoea population dynamics. As an innovative approach, the relationship was modelled by means of generalised additive modelling (GAM models) in a multi-model inference framework.3. The present results on E. chrysorrhoea density and life table analyses suggest that local outbreaks are more likely in coastal habitats where higher mortality was compensated by higher reproductive potential. GAMs turned out to be an effective way to gain a deep understanding of this pattern. Residual mortality was positively and non-linearly related to population density, whereas reproductive potential was not significantly related to any of the variables studied.4. The present study was an attempt to gain a deep understanding of the information derived from descriptive life tables.
Ecological Entomology 03/2011; 36(2):188 - 199. · 2.00 Impact Factor
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ABSTRACT: The browntail moth Euproctis chrysorrhoea is a highly polyphagous univoltine forest pest. Although its young larvae usually overwinter in diapause from early autumn to the beginning of spring, winter larval feeding has been reported when this species feeds on the evergreen woody shrub strawberry tree Arbutus unedo. The present study investigated life-history traits of four populations of E. chrysorrhoea feeding on A. unedo, including phenology of the different life stages, larval feeding activity and diapause incidence. By modelling the relationship between larval size and host plant leaf persistence, elevation and mean annual temperature, we also studied larval development in ten populations of this species sampled from a range of geographical locations in Spain, from both A. unedo and deciduous hosts. The results obtained revealed that on A. unedo, E. chrysorrhoea phenology has shifted: from October to March, A. unedo larvae doubled their size, whereas, on deciduous Ulmus minor and Quercus faginea, larval size did not change. General linear models demonstrated that such differences were not related to environmental variables. We also found that on A. unedo larval feeding was arrested for 2 months, with this period representing a true diapause. The results obtained in the present study suggest that E. chrysorrhoea populations are phenologically adapted to their local host plants, and that the presence of foliage is a key element in the phenological shift reported on A. unedo. These results may have implications with respect to the formation of E. chrysorrhoea host races.
Agricultural and Forest Entomology 11/2010; 12(4):381-388. · 1.60 Impact Factor
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ABSTRACT: Size and age thresholds for pupation are important life history traits of insects. They are the ultimate consequences of the underlying physiological mechanism that optimize resource allocation. Such thresholds may have a plastic response under time-varying environmental conditions, developmental polymorphism (i.e., plasticity in the number of instars before pupation) being a common strategy adopted by insects to overcome this challenging situation. In this study, we systematically explore the variables related with both age and size thresholds for pupation and developmental polymorphism in the browntail moth, Euproctis chrysorrhoea (Lepidoptera: Lymantriidae), by rearing a group of caterpillars under conditions that either emulate larval diapause or prevent it. As an innovative approach, we evaluated the importance of predictor variables by means of generalized linear modeling in a multi-model inference framework. Our results show that (i) rearing conditions affect fitness, (ii) rearing conditions, size of hatchlings, size and age at maturity and sex are related to the number of instars before pupation, and (iii) there are both age and size thresholds for pupation which differ between sexes and between larvae reared under different conditions. Results are discussed in the context of lepidopteran plasticity in life history traits and its relationship with optimal molting strategies.
Journal of insect physiology 08/2009; 55(10):952-8. · 2.24 Impact Factor
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ABSTRACT: The preimaginal stages of T peregrina are described. The egg displays a sculptured chorion, which is found only on those deposited externally. The immature larvae are characterized by their peculiarities in (a) a setose ring on the thoracic and abdominal segments, (b) an anal notch and (c) size and the sensory structures of the head capsule. The final instar is described and illustrated. Morphological structures of diagnostic value are discussed. The most salient character shown by the mature larva of this species lies in the epistoma, which is complete.
Florida Entomologist 03/2007; 90(1):180-183. · 1.36 Impact Factor
