A research team lead by Prof. Jianhua Jin from the School of Life Sciences discovered the first Northern Hemisphere megafossil of Dacrycarpus
Source: School of Life Sciences
Written by: School of Life Sciences
Edited by: Wang Dongmei
East Asia has several biodiversity hotpots and is a key region for understanding the origin and evolution of the biodiversity in the Northern Hemisphere. One of the characteristics of the East Asian flora is that it includes many Gondwana floristic elements which have been widely distributed in the Southern Hemisphere during the geological period. How do these species spread across the equator from the Southern Hemisphere to Asia?
Recently, the team of Prof. Jianhua Jin from the School of Life Sciences at Sun Yat-sen University reported the first Northern Hemisphere megafossil of
Dacrycarpus from the Miocene Erzitang Formation of the Guiping Basin, Guangxi, South China. They reviewed the phytogeographical history of
Dacrycarpus and analysised related geological and climatic events and plant physiological characteristics to discuss the possibility of biotic exchange between Asia and Australia.
Figure 1. Paleogeographical maps of different periods showing the previous macrofossil records, the change of land bridge and the possible immigration route of Dacrycarpus.
Since the late Oligocene, the island chain and ocean current changes caused by the Australian-Asian plate collision have provided land bridges and a suitable humid climate for this transequatorial migration. Moreover, the physiological characteristics of tolerance to being waterlogged and living in extreme environments increased chance of
Dacrycarpus arriving South China. Furthermore, they checked megafossil records of 150 genera of the Tropic Asia to Tropic Australia distribution taxa. The results show that the genus
Dacrycarpus was not the only group entering Asia by this way, suggesting that this event probably facilitated other biotic exchanges across the equator and contributed significantly to Neogene plant diversity in southern Asia, namely the
Dacrycarpus pattern (Figure 1). This study shows that the Australian-Asian plate collision events have promoted cross-equatorial biotic exchanges between the two continents since the late Oligocene, and greatly promoted the diversification of flora in East Asia.
Figure 2. Different organs of Dacrycarpus fossils from the Miocene of South China and modern species Dacrycarpus imbricatus (Blume) de Laubenfels.
Another highlight of this study is the discovery of mummified specimens allowing for the preservation of three-dimensional preserved dimorphic foliage, ovuliferous shoots and male cone with in situ pollen. This study presents the first data on the anatomical structure of seed cone and exine ultrastructure of Dacrycarpus in situ pollen grains from a fossil material using by CT scanning and ultrathin sectioning. Of all the living species, this fossil species shows a close similarity to D. imbricatus in morphological and anatomical characters (Figure 2). Combined with the ecological niche occupied by modern related taxa and the composition of the fossil flora, the studied region of southern China was probably covered by conifer-broadleaved mountain rainforests during the Miocene.
The above study has been published in National Science Review (IF=13.222) and Journal of Systematics and Evolution (IF=4.040). Xinkai Wu, Ph.D. student of the School of Life Sciences at Sun Yat-sen University, is the first author of the two papers, and Prof. Jianhua Jin from the School of Life Sciences at Sun Yat-sen University and Prof. Cheng Quan from Chang’an University are the co-corresponding authors of the two papers.
This study is funded by the Key International (Regional) Joint Research Project and the general project of the National Natural Science Foundation of China, and the middle-term assessment and the completion acceptance of the Key International (Regional) Joint Research Project are rated as excellent.
Link to the papers:
https://doi.org/10.1093/nsr/nwz060
https://doi.org/10.1111/jse.12534
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