Warmer springs disrupt the synchrony of oak and winter moth phenology.

Spring temperatures have increased over the past 25 years, to which a wide variety of organisms have responded. The outstanding question is whether these responses match the temperature-induced shift of the selection pressures acting on these organisms. Organisms have evolved response mechanisms that are only adaptive given the existing relationship between the cues organisms use and the selection pressures acting on them. Global warming may disrupt ecosystem interactions because it alters these relationships and micro-evolution may be slow in tracking these changes. In particular, such shifts have serious consequences for ecosystem functioning for the tight multitrophic interactions involved in the timing of reproduction and growth. We determined the response of winter moth (Operophtera brumata) egg hatching and oak (Quercus robur) bud burst to temperature, a system with strong selection on synchronization. We show that there has been poor synchrony in recent warm springs, which is due to an increase in spring temperatures without a decrease in the incidence of freezing spells in winter. This is a clear warning that such changes in temperature patterns may affect ecosystem interactions more strongly than changes in mean temperature.