The genus Calocedrus Kurz (Cupressaceae) is an evergreen conifer and also known as incense cedar. It contains three relict species and is discontinuously distributed in eastern Asia and western North America. The diversification of this relict genus in the Neogene of eastern Asia has remained unknown due to lack of fossil evidence. 

Prof. ZHOU Zhekun and his team of Xishuangbanna Tropical Botanical Garden (XTBG) discovered fossils from the upper Miocene of Wenshan basin, southeast Yunnan, South China. They recognized it as Calocedrus shengxianensis. The new fossil material included well-preserved leafy twigs and associated seed cones.  

The researchers compared the fossil species with the extant Calocedrus macrolepis. They then discussed the diversity of the genus in the late Miocene, differentiation of the genus in eastern Asia since the late Miocene, and leaf morphological responses and shifts with climatic change. They also made the reassignment of Fokienia shengxianensis as the fossil was originally described. 

Based on the comparisons, the fossil species showed most of similarities with the modern eastern Asian Calocedrus macrolepis Kurz. The differences between them lie primarily in the morphological features of the apex of lateral and (or) facial leaves. For example, the modern species has acute leaf apices, while the fossil one has blunt or obtuse leaf apices.  

With the global cooling and the uplift of the Qinghai–Tibet Plateau, the climatic change has led to morphological shifts of the leaves in Wenshan: the acute or acuminate leaf apices in the modern C. macrolepis compared to the blunt or obtuse ones in the late Miocene C. shengxianensis have evolved probably to adapt to the humid climate since the late Miocene.

The study entitled “Calocedrus shengxianensis, a late Miocene relative of C. macrolepis (Cupressaceae) from South China: Implications for paleoclimate and evolution of the genus” has been published online in Review of Palaeobotany and Palynology.

Fossil foliage of Calocedrus shengxianensis (He, Sun et Liu) Zhang et Zhou comb. nov.1–2. (Image by ZHANG Jianwei) 

Contact:
ZHOU Zhekun, Ph.D Principal Investigator 
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences,
Mengla, Yunnan 666303, China
Tel: 86 691 8716932
Fax: 86 691 8715070
E-mail: zhouzk@xtbg.ac.cn