1 Phenotypic biomarkers of climatic impacts on declining insect populations: a key role for 2 decadal drought, thermal buffering and amplification effects and host plant dynamics 3 4 Jofre Carnicer1,2*, Constantí Stefanescu2,3, Maria Vives-Ingla1, Carlos López2, Sofia Cortizas1, 5 Christopher Wheat4, Roger Vila5, Joan Llusià2, Josep Peñuelas2 6 7 1Department of Evolutionary Biology, Ecology and Environmental Sciences, University of Barcelona, 8 08028 Barcelona, Spain 9 2CREAF, Global Ecology Unit, Autonomous University of Barcelona, 08193 Cerdanyola del Vallès, 10 Spain 11 3Natural History Museum of Granollers, E-08402 Granollers, Spain 12 4Department of Zoology (Population Genetics), University of Stockholm, Svante Arrheniusväg 13 18B, Stockholm University, S-10691 Stockholm, Sweden 14 5Institute of Evolutionary Biology (CSIC-UPF), 08003 Barcelona, Spain 15 16 Corresponding author:
[email protected] 17 18 Running head: Phenotypic biomarkers of climate impacts and insect population declines. 19 20 Keywords: climate change, butterflies, phenotypic biomarker, multiannual drought, thermal 21 buffering, host plant, Pieris napi. 22 23 Type of paper: primary research article. 24 25 26 27 1 1 Abstract 2 3 1. Widespread population declines have been reported for diverse Mediterranean 4 butterflies over the last three decades, and have been significantly associated to 5 increased global change impacts. The specific landscape and climatic drivers of these 6 declines remain uncertain for most declining species. 7 2. Here we analyse whether plastic phenotypic traits of a model butterfly species (Pieris 8 napi) perform as reliable biomarkers of vulnerability to extreme temperature impacts in 9 natural populations, showing contrasting trends in thermally exposed and thermally 10 buffered populations.