Seasonal timing in a warming world: Plasticity of seasonal timing of growth and reproduction

In seasonal environments the timing of various biological processes is crucial for growth, survival and reproductive success of an individual. Nowadays, rapid large-scale climate change is altering species’ seasonal timing (phenology) in many eco¬systems. In this thesis Lucia Salis focuses on the study of seasonal timing in the food chain of the oak-winter moth-great tit. As temperature increased over the last decades, both phenologies of the host plant, the oak, and the herbivorous insect, the winter moth, have advanced. However, timing of egg-hatching in the winter moth has advanced more than the oak bud burst leading to the phenological mismatch and increased selection for later egg-hatching. In turn, as a result of the earlier phenology of the insects, a phenological mismatch has occurred between the great tit offspring’s food demand and the peak in caterpillars’ biomass, leading to enhanced selection for earlier egg-laying on the birds. The work presented in this thesis show that winter moth have adapted to warmer temperatures via microevolutionary shift in timing of egg-hatching. Next, the influence of temperature and photoperiod on the phenology of the entire life-cycle in the winter moth and the timing of reproduction in the great tit is investigated. Finally, this research deepens our understanding of the mechanisms underlying seasonal timing and ultimately forecast the rate of adaptation to changing conditions