Why do oaks (Quercus spp.) have lobed leaves?

Poster presented at the XX International Botanical Conference, Madrid, Spain, July 21–27, 2024.

Authors:

Kristel van Zuijlen¹, Thomas Denk¹

Affiliation:

1. Swedish Museum of Natural History, Stockholm, Sweden

Abstract:

Lobed leaves are a characteristic feature of oak trees (Quercus L., Fagaceae) although only a subset of the more than 400 species do possess such leaves. Oaks became abundant in the northern hemisphere during the early Eocene (ca. 50 million years, myrs, ago) but the first records of deeply lobed leaves are only known from Oligocene deposits, at least 15 myrs later. Lobed leaves started to radiate during the Eocene-Oligocene transition (EOT, ca. 34 myrs ago), which denotes the most dramatic global drop in temperature during the past 65 million years. We aim to assess how lobed leaves and other leaf characteristics are distributed across the global oak phylogeny and how their distribution is constrained by climate. To do this, we compiled leaf traits and climate envelopes for all modern oak species. We then used the extensive leaf fossil record and past climate reconstructions to trace the origin of lobed oak leaves.