Host-plant use in the range expansion of the pine processionary moth, Thaumetopoea pityocampa |
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Authors: | MICHAEL STASTNY REA BATTISTI EDOARDO PETRUCCO-TOFFOLO FREDRIK SCHLYTER STIG LARSSON |
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Institution: | Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, U.S.A.;, Department of Environmental Agronomy –Entomology, University of Padova, Agripolis, Legnaro, Italy;, Chemical Ecology, Department of Crop Sciences, Swedish University of Agricultural Sciences, Alnarp, Sweden;, and Department of Entomology, Swedish University of Agricultural Sciences, Uppsala, Sweden |
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Abstract: | Abstract. 1. During range expansions of phytophagous insects, secondary or novel hosts may allow colonisation of areas without primary hosts. Because plant species often differ in their relative attractiveness and suitability for insects, insect preference for, and performance on, these hosts can determine recruitment potential in the current and future expansion areas. 2. This study explores the relative roles of female preference and larval performance in an important pine defoliator, Thaumetopoea pityocampa (Denis & Schiffermüller) (Lepidoptera, Notodontidae), which colonises three Pinus species at its current range margin in the Italian Alps: P. nigra (primary host), P. sylvestris (secondary host), and P. mugo (novel host). 3. Host use patterns in multiple insect populations were studied through choice and no-choice oviposition experiments in cages, field surveys of mixed stands, and laboratory and field monitoring of larval growth and mortality. It was predicted that a specific life-history trait – time limitation of short-lived females to lay a single batch of eggs – would act as a component of female performance, and lead to similar rates of host acceptance in no-choice settings. 4. In the choice experiment, P. nigra was accepted the most frequently while P. sylvestris was accepted the least frequently, confirming nest density patterns in the field. Contrary to prediction, females remained discriminating in no-choice settings in spite of time limitation. In contrast, relative growth rate (RGR) and mortality of larvae did not differ significantly among the three hosts, highlighting a discrepancy between female preference and larval performance. 5. Recruitment potential of T. pityocampa in future expansion into stands of P. sylvestris and P. mugo is evaluated by combining host quality, conservatism in oviposition behaviour, habitat suitability, and the opportunity for local adaptation. |
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Keywords: | Female longevity host plants host preference larval performance life history oviposition Pinus nigra Pinus sylvestris Pinus mugo range expansion |
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