Temperature niche shift observed in a Lepidoptera population under allochronic divergence

Authors

  • H. SANTOS,

    1. Centro de Estudos Florestais (CEF), Instituto Superior de Agronomia (ISA), Technical University of Lisbon (UTL), Lisbon, Portugal
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  • M. R. PAIVA,

    1. Centro de Estudos Florestais (CEF), Instituto Superior de Agronomia (ISA), Technical University of Lisbon (UTL), Lisbon, Portugal
    2. DCEA, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, Caparica, Portugal
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  • C. TAVARES,

    1. Centro de Estudos Florestais (CEF), Instituto Superior de Agronomia (ISA), Technical University of Lisbon (UTL), Lisbon, Portugal
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  • C. KERDELHUÉ,

    1. INRA Centre de Bordeaux, UMR1202 BIOGECO, Cestas cedex, France
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    • Present address: INRA Centre de Montpellier, UMR CBGP (INRA/IRD/Cirad/Montpellier SupAgro), Campus International de Baillarguet, CS 30016, F-34988 Montferrier-sur-Lez cedex, France.

  • M. BRANCO

    1. Centro de Estudos Florestais (CEF), Instituto Superior de Agronomia (ISA), Technical University of Lisbon (UTL), Lisbon, Portugal
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Manuela Branco, Centro de Estudos Florestais, Instituto Superior de Agronomia, Technical University of Lisbon, Tapada da Ajuda, 1349-017 Lisbon, Portugal.
Tel.: +351 213653382; fax: +351 213653388; e-mail: mrbranco@isa.utl.pt

Abstract

A process of adaptive divergence for tolerance to high temperatures was identified using a rare model system, consisting of two sympatric populations of a Lepidoptera (Thaumetopoea pityocampa) with different life cycle timings, a ‘mutant’ population with summer larval development, Leiria SP, and the founder natural population, having winter larval development, Leiria WP. A third, allopatric population (Bordeaux WP) was also studied. First and second instar larvae were experimentally exposed to daily-cycles of heat treatment reaching maximum values of 36, 38, 40 and 42 °C; control groups placed at 25 °C. A lethal temperature effect was only significant at 42 °C, for Leiria SP, whereas all temperatures tested had a significant negative effect upon Leiria WP, thus indicating an upper threshold of survival c.a. 6 °C above that of the WP. Cox regression model, for pooled heat treatments, predicted mortality hazard to increase for Leiria WP (+108%) and Bordeaux WP (+78%) in contrast to Leiria SP; to increase by 24% for each additional °C; and to decrease by 53% from first to second instar larvae. High variability among individuals was observed, a population characteristic that may favour selection and consequent adaptation. Present findings provide an example of ecological differentiation, following a process of allochronic divergence. Results further contribute to a better understanding of the implications of climate change for ecological genetics.

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