Evolutionary Biology Of Some Important Plant Taxa And Their Paleoenvironments From The Mid-Miocene Of Shanwang, Shandong Province, China

The Shanwang flora is Miocene in age and first reported by Hu and Chaney in 1940. Revisions on the flora were partly carried out by R.W. Brown in 1946, and WGCPC in 1978. Some taxa were added to this flora by H-M Li in 1981 and J-R Tao in 1992. This flora is composed largely of angiosperms, including 43 families, 87 genera and 125 species. These families of angiosperms are mainly typical temperate trees, such as those in Betulaceae, Aceraceae, Ulmaceae, Fagaceae, Salicaceae, Tiliaceae, Juglandaceae and Rhamnaceae, and some subtropical evergreen trees, i.e. Cinnamomum (Lauraceae), Magnolia (Magnoliaceae), Ficus (Moraceae), and Eriobotrya (Rosaceae). The paleoclimate inferred from this Shanwang flora and its associated fauna is warm temperate to subtropical. Recent investigations provide new data into Shanwang flora. The new genus of winged fruits Chaneya, new species of Zelkova, and new records of Eucommia and Keteleeria are established respectively.The living trees of Eucommia ulmoides, an endemic species in China, grow from 200m to 1700m above sea level, within the geographic range from 102°E to 118°E and from 25°N to 35°N. Spring temperatures in these regions vary from 12.3℃ to 20.1℃. A physiological study (using germination tests) of E. ulmoides has been undertaken to test the role of spring temperature as a factor controlling the distribution of Eucommia.Results show that the spring temperature is a limiting factor for Eucommia seed germination and hence for the distribution pattern of the genus. The most suitable range of temperature for seed germination, established experimentally, is from 13℃ to 22℃, with an optimum of 18℃. Specimens of fossil Eucommia cf. ulmoides, preserved as a branch segment and leaves, showing the distinctive latex, were found in Middle Miocene sediments of Shanwang Formation, Shandong Province, East China. If the climatic tolerances documented here for E. ulmoides are extrapolated to Shanwang, they are in fact consistent with other predictions of the paleoclimate at this site, indicative of the potential value of Eucommia as a biothermometer. These Miocene fossils, and one previously described Eocene fruit specimen, prove the former existence of Eucommia in China in addition to North America and Europe. This confirms that the genus is not a recent arrival in China, refutes previous suggestions that the genus migrated to China from North America via Europe during the Tertiary, and extends our understanding of the past biogeography of the genus.Keteleeria today grows in China, Vienan and Laos, East Asia with 3 extant species, K. fortunei, K. davidiana and K. evelyniana. The genus was preserved as cones, scales, winged seeds, shoots, leaves and woods found widely in the Tertiary sediments of North Hemisphere, ranging from Oligocene to Miocene in Oregon, western USA, Miocene in Middle Europe, Miocene to Pliocene in Japan, and Oligocene to Miocene in Far East region of Russia, East Asia. The Keteleerias lived until late Miocene in North America, early Pleistocene in Europe (? Pollen data) and end of Pliocene in Japan, East Asia, and finally grow in subtropical to north tropical hill regions of South China, i.e., towards south parts of Qinglin Mounts and Yangzi river, east part of Yalongjiang river, Taiwan, and Hainan island, some populations of K. evelyniana extends to North Vienan and Laos.The fossil cones of Keteleeria recognized from Shanwang flora aged as mid-Miocene in China and Rujada flora dated as Oligocene in western USA are much closer to the living species of K. fortunei. The fossil cones reported from both Miocene to Pliocene inJapan and Miocene in USA are related to living K. davidiana. These evidence support that a close flora relationship exists between Eastern Asia and North America in the Tertiary. The fossil cone found in Shanwang represents an early type having common characters with both extant species of K. fortunei and K. davidiana. The finds indicate the species divergence of both living species mentioned above might be a relatively recent event occurring i...