Masterarbeit

Traits to Live or Traits to Die? – Tracing the Development of Functional Diversity in Trees During Cenozoic Climate Change

Vincent Wilkens (03/2023-09/2023)

Betreuer: Carl Beierkuhnlein, Anna Walentowitz

The native tree flora of northwestern Europe today represents the aftermath of a series of climate-induced extinction events spanning the Cenozoic era (66 Ma – present). The evolutionary pressures have varied both in tempo and in nature, from long-term cooling that began in the Middle Eocene, to accelerated cooling during the Plio-Pleistocene transition, which then culminated in repeated glacial cycles over the Pleistocene. The contemporary challenge of adapting European forests to current and future climate change demands an understanding of how trees have responded to different climatic changes in the past. The purpose of this study is to investigate trends in the evolution of genus-level diversity in trees over the course of the Cenozoic. Namely, I test the hypothesis that the selective processes by which some genera persisted, while others perished, were not random, but driven by favorable or unfavorable traits. I explore changes in trait values associated with different climatic changes. I show that the evolutionary outcomes of genera can be predicted with high accuracy using traits alone amid climatic changes of rapid tempo (over less than a few million years), such as during the Plio-Pleistocene transition and subsequent glaciations, but not over long-term cooling that spanned tens of millions of years from the Eocene to the Pliocene. Traits such as photosynthetic rate, lifespan, leaf density, stem specific density, and height were found to be highly correlated with probability of survival. These results underscore the risk posed by future rapid warming scenarios, projected to take place on a timescale even shorter than the rapid climatic changes that devastated European tree diversity during the Plio- Pleistocene transition.