Epsilon Open Archive

Abstract

Many species are expected to advance their phenology in response to global warming. As some interactions are dependent on the interacting species being synchronized in time, it is important to assess whether species shift their phenology in synchrony or not. Whether or not they do will dictate how communities and ecosystem functioning respond to climate change. Species-specific phenological responses could shift interaction strengths, with possible consequences for species fitness. In the context of a community of interacting species, phenological shifts can modify the interaction network and allow new interactions to occur and cause old interactions to disappear. In addition, if populations are locally adapted to temperature, then local communities might differ in their phenological response.

In this thesis, I aim to explore how temperature influence the phenology of different species and populations and how this is reflected in the structure of a community. To this aim, I focus on a tri-trophic community consisting of Quercus robur, its insect herbivores and associated parasitoids. I assess i) how temperature influence spring phenology of acorns and insects associated with Q. robur ii) how temperature influence the spring and autumn phenology of Q. robur, and whether oak genotypes differ in their response, and iii) how variation in Q. robur phenology is reflected in the structure of the insect community.

I detected that both species and populations differed in their response to temperature. I also found that overwintering temperatures influenced the timing of bud burst in Q. robur. In autumn, warm temperatures in spring advanced phenology, while leaf coloration was delayed for Q. robur growing at warmer locations. Interestingly, both the timing of spring and autumn phenology influenced the structure of the herbivore community, while Q. robur phenology had no detectable impact on the performance of herbivores in summer.

Overall, my findings suggest that temperature-induced changes in phenology can alter the temporal overlap between species, and that such changes affect the community structure. If the population-specific responses to temperature observed here extend widely across species, then local communities will differ in their response to temperature. With a changing climate, these patterns may result in changes in community structure for species active in spring and autumn, with different responses among local communities. This complicates current predictions regarding the biotic responses to ongoing climate change.