Numerical Taxonomy Of Winged Fruits And Paleoenvironmental Reconstraction Based On Angiosperm Leaves From The Neogene Of West Yunnan

The west of Yunnan Province locates in the south of the Hengduan Mountains and southeast margin of the Qinghai-Tibet Plateau, where well-preserved plant fossils were sampled in the current research. West Yunnan is one of the best localities not only for modern plants diversified, but also for preservation of Cenozoic plant fossils. The present study on Neogene fossil plants can provide evidence for plant systematics and evolution, and furthermore, it may strengthen our knowledge about the origin of plant diversity in China. Moreover, we can also acquire the knowledge about paleoclimatic evolution and paleoenvironmental changes. Thereby, we can get the information about the influence of the Late Cenozoic movement on West Yunnan's environment.The numerical taxonomy on Palaeocarya specimens suggests that four species were recognized, and they were assigned to Palaeocarya guangxiensis, Palaeocarya koreanica, Palaeocarya longialata sp. nov., and Palaeocarya yunnanensis sp.nov. These fossil species are much similar to Engelhardia species that now inhabit Southeast Asia and South China, and they may be close relatives. Engelhardieae species from the Pliocene to today moved southward or maintained at lower latitudes while the more northerly populations became extinct provides additional evidence that Neogene cooling affected the north/south latitudinal distributions of the Engelhardieae and many other plant species.The clustering based on morphological characters assign specimens of Acer fruits into seven types. They are Acer subpictum, Acer miofranchetii, Acer browni, Acer macrocarpium sp. nov., Acer globicarpium sp. nov., Acer tengchongense sp. nov., and Acer sp. The cladistic analysis showed that the fossil species of Acer much diversified in morphology and may be at different evolutional levels, even some species have evolved into comparative levels with certain extant Acer species.We also conduct paleoclimatic reconstruction based on the leaf physiognomy of angiosperm fossils with the methodology of univariate and multivariate statistics. The results demonstrated that the univariate analysis abtain a higher result than the multivariate method. The multivariate program (CLAMP) acquired the following climate values: mean annual temperature (MAT; 17.16～17.68℃), warm month mean temperature (WMMT; 25～25.5℃), cold month mean temperature (CMMT; 9.54～10.8℃), length of the growing season (GRS; 9.71～9.5 months), growing season precipitation (GSP; 183.43～190.12cm), mean monthly growing season precipitation (MMGSP; 22.24～23.05cm), precipitation during the three consecutive wettest months (3WET; 89.21～91.78cm), precipitation during the three consecutive driest months (3DRY; 47.45～51.28cm), relative humidity(RH, 76.65～77.75%), specific humidity (SH, 10.74～10.79), and Enthalpy (ENTHAL, 318.4～319.7 kj/kg).We also investigated the stomatal indices and carbon isotope composition of fossil angiosperm leaves, and then calculated paleo-CO₂ level and phytophysiological parameters in Pliocene. The results show stoma-based paleo-CO₂ estimates is consistent with the independent evidence of geochemistry from marine foraminifera. The paleo-CO₂ level in Early Pliocene is higher than current levels. The carbon isotope discrimination of fossil plants is also higher than that of their nearest living relatives (NLRs), whereas, water use efficiencies of the fossils is lower than that of their NLRs, which confirmed the climate of Early Pliocene was more humid and warmer than it is now. The stomatal data also demonstrate slightly lower Paleo-CO₂ concentration in the Late Pliocene than today.