title: Temperature niche shift observed in a Lepidoptera population under allochronic divergence.
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.
authors.affiliation: Centro de Estudos Florestais (CEF), Instituto Superior de Agronomia (ISA), Technical University of Lisbon (UTL), Lisbon, Portugal.
authors.forename: H
authors.initials: H
authors.lastname: Santos
authors.forename: M R
authors.initials: MR
authors.lastname: Paiva
authors.forename: C
authors.initials: C
authors.lastname: Tavares
authors.forename: C
authors.initials: C
authors.lastname: Kerdelhué
authors.forename: M
authors.initials: M
authors.lastname: Branco
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D005075:Biological Evolution; D006358:Hot Temperature; D007814:Larva / Q000502:physiology; D007915:Lepidoptera / Q000502:physiology*; D011110:Polymorphism, Genetic; D012621:Seasons