The Study Of Carpinus Bract Fossils Features From The Early Miocene Of Maguan,Southeast Yunnan And The Spatial And Temporal Distribution Of Carpinus Genus

In the temperate forest flora of the northern hemisphere,east Asia shows higher biodiversity than North America and Europe at the same latitude,For example,there are about 50 species of Carpinus,46 of which are distributed in east Asia,but the evolutionary history of the species' diversity in east Asia is still unclear.Fossil is the direct evidence of the existence and evolution of plants in geological period,which plays an irreplaceable role in understanding the diversity and evolution of plants.In this paper,33 fossil specimens of carpinus from the lower Miocene strata in the maguan area of southeast yunnan were systematically studied,and the genus and species classification characteristics were compared and discussed in detail.And the morphological characteristics of Carpinus bracts in manguan area were systematically described.6 species of carpinus were identified,including 2 new species and 4 allied species: Carpinus cf.fangiana Hu;Carpinus sp.;Carpinus Maguanensis L.Xue,L.B.Jia,S.T.Zhang sp.nov.;Carpinus cf.chuniana Hu;Carpinus cf.mollicoma Hu;Carpinus cf.pubescens Burk..Among them,two species,Carpinus sp.and C.Maguanensis,are extinct species with entire margin of bract.Through the study of Carpinus fossils in manguan,we can at least draw the following conclusions:(1)6 species of Carpinus have been found in a narrow geographical area of manguan,indicating that the species had a high diversity in the area since early Miocene.(2)There are 2 extinct species in the genus Carpinus in Maguan,which are represented by the entire margin of bract.This indicates that the extinction of Carpinus exists in the evolution of East Asia plant.(3)The evolution of Carpinus may be closely related to the high heterogeneity of the environment in East Asia.It is a process of accumulation of diversity over time.For example,the 2 newly published species may have been newly differentiated due to the founder effect.(4)Carpinus is an important molecule in karst limestone mountains in southeastern Yunnan.The discovery of various Carpinus species in southeastern Yunnan may indicate that karst forests existed in Miocene.The first three points indicate that the evolution of Carpinus is a coexistence model of "Museum" and "Cradle",but as far as "Museum" is concerned,it does not mean that there is no extinction.In addition,this paper collects and collates the modern distribution data and fossil records of Carpinus species,and comprehensively discusses the distribution characteristicsof Carpinus species diversity center,which is its diversity center in southwestern China in East Asia.,and the temporal and spatial evolution of Carpinus in geological period.There is an inseparable relationship between the spatiotemporal evolution law and the paleoenvironment:(1)Based on the distribution of relative pollen genera and C.japonica,the fundamental taxa of Carpinus,we speculate that the genus may originate in East Asia and then spread to Europe and North America.(2)The Miocene is a period of flourishing development of the genus Carpinus,which has a very high species diversity.(3)In Europe,America and Central Asia,the extinction of Carpinus exists,but the reasons for extinction are different between the former 2 and the latter.