As the only direct evidence of past life, fossils provide important information on the interactions between plants and environmental change. Comparing closely related fossils from different geological periods is an efficient method to understand how plants respond to climatic change across a large scale.
In the recent study, Prof. Zhou's group investigated detailed micro-morphology of a dominant element in Neogene fossil sites, Quercus delavayi complex- one oak species- to answer this question.
The results showed that Quercus delavayi complex from different periods share similar leaf morphology, but differ with respect to trichome and stomatal densities. The stomatal density of the Q. delavayi complex was the highest during the late Miocene, declined in the late Pliocene, and then increased during the present epoch.
These values showed an inverse relationship with atmospheric CO2 concentrations. Since the late Miocene, a gradual reduction in trichome base density has occurred in this complex. This trend is the opposite of that of precipitation, indicating that increased trichome density is not an adaptation to dry environments.
These results are important to understand the relationship between plant evolution and climatic change which are important to predict the fate of current biodiversity in a changing environment.
The study is published in Chinese science bulletin.