Fossil leaves of Ficus microtrivia and ficus trivia leaves (2) in the Miocene Wenshan flora(1); fossil and live species have fine veined adenotic structures on the surface (3-5)
(1) Fig wedge leaf growing on limestone bare rock; (2) Emerging limestone shrub vegetation in southeast Yunnan
According to the Xishuangbanna Tropical Botanical Garden of the Chinese Academy of Sciences (Huang Jian): Ficus is one of the most diverse and widely distributed woody plants, with more than 750 species in the world, of which nearly 2/3 species are distributed in tropical Asia.uux.cn The habitats and morphologies of Ficus are extremely diverse, widely distributed in various tropical and subtropical vegetation types from wet to arid, and their morphology and habits have a high correlation with the position of the system within the genus.
In southwest China and Southeast Asia, there are the most typical lime karst (also known as karst) landforms, which have unique geological landforms and physical and chemical properties, drought and high calcium are its most important characteristics, and the vegetation covered on it is also different from the zonal vegetation in terms of species composition and physiological ecology. The most typical is shrub-type vegetation composed of shrubs that grow in bare rock crevices, and many ficus plants are the dominant taxa in this vegetation type. There has been debate as to whether this vegetation is the top of human disturbance or natural succession.
Assistant researcher Huang Jian of the Paleoecology Research Group of Banna Botanical Garden has conducted long-term paleobotanical research in the Wenshan Basin, the core of the lime karst area in southeast Yunnan, and recently found a leaf fossil of ficus species in it. Through the study and summary of the leaf vein structure characteristics of the plants of the genus Ficus, the leaf vein patterns of the genus Ficus are divided into four types, and the leaf vein characteristics of each subgenera are summarized. After leaf structure reconstruction and modern species comparison, it was determined that the ficus fossil in the Wenshan flora belonged to the subgenus Fig (Subgen. Ficus), whose nearest living relative is Ficus trivia. Ficus cuneiformis and similar taxa are distributed in southwest China and northern Vietnam, growing only in shrublands on limestone ridges. Combined with other endemic limestone shrubs found in flora, it is suggested that this type of vegetation already existed in the Miocene (about 15 million years ago) and may have developed on harsher standing conditions. At the same time, the structure of the "veinlets gland" observed on the surface of fossil leaves is exactly consistent with the surface of some existing banyan leaves, and the main function of this structure may be calcium drainage, which is an adaptation to limestone habitats. The species diversity of the Wenshan flora is much higher than that of the ancient flora in the adjacent area, and the diversity of habitats (the simultaneous existence of limestone vegetation and non-limestone vegetation) is an important reason.
The findings, titled A fossil fig from the Miocene of southwestern China: Indication of persistent deep time karst vegetation, were published in the international paleobotanical journal Review of Palaeobotany and Palynology.
The research was funded by the National Fund of China (U1502231, 41661134049), the "Western Light" Young Talents Project of the Chinese Academy of Sciences, the "135" Project Direction I of Banna Park (2017XTBG-F01), and the Southeast Asian Center of the Chinese Academy of Sciences (Y4ZK111B01).
Related: Fossil discoveries of ficus wedges confirm the long-term existence of limestone shrublands
uux.cn According to Science and Technology Daily (Zhao Hanbin): Is the shrub-type vegetation that grows in the crevices of bare rock, especially fig plants, formed by human interference, or is it the top of natural succession? There has been debate in academic circles. A recent publication in the international paleobotanical journal Paleobotany and Pollenology by the Xishuangbanna Institute of Tropical Botany, Chinese Academy of Sciences, helps clarify this issue.
Ficus is one of the most diverse and widely distributed woody plants, with more than 750 species worldwide, nearly two-thirds of which are distributed in tropical Asia. The habitats and morphologies of Ficus are diverse, widely distributed in various tropical and subtropical vegetation types from wet to arid, and their morphology and habits have a high correlation with the systematic position within the genus.
In southwest China and Southeast Asia, lime karst landforms are the most typical, drought and high calcium are its most important characteristics, and the vegetation covered on it is also different from zonal vegetation in terms of species composition and physiological ecology.
Huang Jian, assistant researcher of the Paleoecology Research Group of Xishuangbanna Tropical Botanical Garden, conducted long-term paleobotanical research in the Wenshan Basin, the core of the lime karst area in southeast Yunnan, and found a leaf fossil of ficus genus. After in-depth study of the leaf vein structure characteristics of the living Fig and subgenus plants, he divided the leaf vein patterns of the genus Ficus into four types. After leaf structure reconstruction and modern species comparison, it was determined that the fossil of this ficus genus in the Wenshan flora belonged to the fig subgenus, and its nearest living relative was Ficus cuneiformis.
Ficus cuneiformis and similar taxa are distributed in southwest China and northern Vietnam, growing only in limestone ridge shrublands. Combined with other endemic plants found in the flora, it is suggested that this type of vegetation existed in the Miocene about 15 million years ago, and it may have developed on harsh standing conditions. At the same time, the fine veined adenal structure observed on the surface of fossil leaves is exactly the same as that of some living banyan leaves, and the main function of this structure may be calcium excretion, which is an adaptation to limestone habitats. The species diversity of wenshan flora is much higher than that of ancient flora in the neighboring area, and the diversity of habitats such as limestone vegetation and non-limestone vegetation coexist is an important reason.
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