Yu-Sheng (Christopher) Liu

Fossil Cathaya (Pinaceae) Pollen from the Canadian High Arctic

Palynological studies of the Eocene Buchanan Lake Formation, Axel Heiberg Island, Canadian High Arctic, have yielded pollen grains closely comparable to those of extant Cathaya Chun et Kuang, a paleoendemic conifer of southwestern China. These palynomorphs are assigned to Cathaya gaussenii Sivak, which is here interpreted as the only species to which known fossil pollen of this genus can be assigned. Unless scanning electron microscopy is used, generic affinity cannot be determined with certainty. On the basis of light microscopy alone, Cathaya‐like pollen fossils may be grouped into one form‐taxon, Pityosporites microalatus (Potonié) Thomson et Pflug. The Eocene record from Canada provides convincing evidence for the occurrence of Cathaya in North America and is consistent with interpretations for warm climatic conditions in the Canadian Arctic in the Middle to Late Eocene. An appraisal of the available literature on fossil Cathaya and Cathaya‐like pollen of Cretaceous to Recent age has been undertaken. The pre‐Cretaceous record is difficult to evaluate. The genus Cathaya was apparently restricted to North America and East Asia during the Cretaceous but had dispersed to Europe, possibly via a North Atlantic land bridge, by the Early Tertiary. In the Neogene, Cathaya became widespread in North America, East Asia, and Europe. Late Tertiary climatic deterioration and Quaternary glaciation appears to have been responsible for extirpation of Cathaya from North America first (latest record Late Miocene), and then from Europe (Pleistocene). Therefore, the endemic distribution of extant Cathaya in China represents a remnant of a formerly widespread Asiatic population.

Paleogene evolution of precipitation in northeastern China supporting the middle Eocene intensification of the East Asian monsoon

ABSTRACT The timing of the development of the East Asian monsoon in the geologic past is critically important for paleoclimatological studies, yet few quantitative data are available. Based on palynomorphs from six formations, supplemented by leaf fossils from one of these formations in Fushun, northeastern China, we present a quantitative estimate of the evolution of precipitation in this area during the middle Paleocene–late Eocene. The results demonstrate that seasonal precipitation prevailed during the interval, suggesting that the monsoonal system had already developed by this time. Comparing Paleogene climatic results from different latitudes in eastern China, we conclude that the East Asian monsoon must have been significantly enhanced after the late middle Eocene (∼41–40 Ma), due to increased precipitation differentiation between wet and dry months as shown in the present study. The influence of both the uplift of the Da Hinggan Mountains in northeastern Asia on regional topography and the India-Asia collision globally may have contributed to early monsoon intensification by their influence on air mass movement and associated precipitation patterns in the monsoonal realm.

LEAF MARGIN ANALYSIS: A NEW EQUATION FROM HUMID TO MESIC FORESTS IN CHINA

Abstract Leaf margin analysis (LMA) is a widely used method that applies present-day linear correlation between the proportion of woody dicotyledonous species with untoothed leaves (P) and mean annual temperature (MAT) to estimate paleotemperatures from fossil leaf floras. Previous works demonstrate that LMA shows regional constraints and to date, no equation has been modeled directly from Chinese forests. Fifty humid to mesic Chinese forests were chosen to understand the relationship between percentage of untoothed leaf species and MAT in China. Consistent with previous studies, the Chinese data indicate that P shows a strong linear correlation with MAT, but the actual relationship is a little different from those recognized from other regions. Among the several currently used LMA equations, the one resulting from North and Central American and Japanese data, rather than the widely used East Asian LMA equation, yields the closest values to the actual MATs of the Chinese samples (mean absolute error = 1.9 °C). A new equation derived from the Chinese forests is therefore developed, where MAT = 1.038 + 27.6 × P. This study not only demonstrates the similarity of the relationship between P and MAT in the Northern Hemisphere, but also improves the reliability of LMA for paleoclimate reconstructions of Chinese paleofloras.

Lagerstroemia (Lythraceae) pollen from the Miocene of eastern China

A newly discovered fossil pollen taxon is described as Lagerstroemia cathayensis sp. nov. on the basis of a combination of morphological characters including prolate shape with no or weakly developed pseudocolpi and rugulate‐verrucate tectum. The fossil pollen was recovered from a Miocene deposit in Zhejiang province, eastern China. It resembles pollen of extant Lagerstroemia subcostata Koehne and L. limii Merrill, both species still occurring near the fossil site in Zhejiang province and further extending into other regions of southern China, Japan, India and the Philippines. This record represents the only description of Cenozoic pollen grains of the genus Lagerstroemia from East Asia examined by means of scanning electron microscopy. The occurrence of Lagerstroemia together with some temperate plants (i.e. Keteleeria, Acer, Carpinus, Fagus) at the fossil site suggests that the climate in eastern China during the Miocene was similar to that of today.

First Oligocene mummified plant Lagerstätte at the low latitudes of East Asia

1 Research Center of Paleontology and Stratigraphy, Jilin University, Changchun 130026, China; 2 State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China; 3 Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China; 4 Office of Research and Graduate Studies, Prairie View A & M University, Texas 77446, USA

Resilience of plant-insect interactions in an oak lineage through Quaternary climate change

Abstract. Plant-insect interactions are vital for structuring terrestrial ecosystems. It is still unclear how climate change in geological time might have shaped plant-insect interactions leading to modern ecosystems. We investigated the effect of Quaternary climate change on plant-insect interactions by observing insect herbivory on leaves of an evergreen sclerophyllous oak lineage (Quercus section Heterobalanus, HET) from a late Pliocene flora and eight living forests in southwestern China. Among the modern HET populations investigated, the damage diversity tends to be higher in warmer and wetter climates. Even though the climate of the fossil flora was warmer and wetter than modern sample sites, the damage diversity is lower in the fossil flora than in modern HET populations. Eleven out of 18 damage types in modern HET populations are observed in the fossil flora. All damage types in the fossil flora, except for one distinctive gall type, are found in modern HET populations. These results indicate that Quaternary climate change did not cause extensive extinction of insect herbivores in HET forests. The accumulation of a more diverse herbivore fauna over time supports the view of plant species as evolutionary “islands” for colonization and turnover of insect species.

Miocene shift of European atmospheric circulation from trade wind to westerlies

The modern European climatic regime is peculiar, due to its unitary winter but diverse summer climates and a pronounced Mediterranean climate in the south. However, little is known on its evolution in the deep time. Here we reconstruct the European summer climate conditions in the Tortonian (11.62–7.246 Ma) using plant fossil assemblages from 75 well-dated sites across Europe. Our results clearly show that the Tortonian Europe mainly had humid to subhumid summers and no arid climate has been conclusively detected, indicating that the summer-dry Mediterranean-type climate has not yet been established along most of the Mediterranean coast at least by the Tortonian. More importantly, the reconstructed distribution pattern of summer precipitation reveals that the Tortonian European must have largely been controlled by westerlies, resulting in higher precipitation in the west and the lower in the east. The Tortonian westerly wind field appears to differ principally from the trade wind pattern of the preceding Serravallian (13.82–11.62 Ma), recently deduced from herpetofaunal fossils. Such a shift in atmospheric circulation, if ever occurred, might result from the development of ice caps and glaciers in the polar region during the Late Miocene global cooling, the then reorganization of oceanic circulation, and/or the Himalayan-Tibetan uplift.

First fossil record of Staphylea L. (Staphyleaceae) from North America, and its biogeographic implications

The occurrences of Staphylea L. (Staphyleaceae) fossils have been abundantly documented from the Cenozoic of Eurasia, but none has been confirmed from North America to date. In this study, we describe Staphylealevisemia sp. nov. on the basis of seed remains from the latest Miocene to earliest Pliocene of northeastern Tennessee, southeastern USA. The seeds are characterized by a smoothly inflated body, a large hilar scar perforated by several vascular traces and bordered by a distinctive lip-like rim, a cuticle coating the seed coat interior, and seed coat section containing weakly developed tiny lumina. According to the paleogeographic distribution of the genus, it is hypothesized that Staphylea originated from western Eurasia no later than the late Oligocene, and arrived in eastern North America no later than the late Neogene, most possibly through the North Atlantic land bridges like many other seed plants.

Floristic implications of two contemporaneous inland upper Neogene sites in the eastern US: Pipe Creek Sinkhole, Indiana, and the Gray Fossil Site, Tennessee (USA)

Late Neogene floras of North America are mainly represented by sites located along the east coast Piedmont and the Great Plains. To date, there are only two upper Neogene inland localities in the eastern half of North America, the Pipe Creek Sinkhole (Indiana) and the Gray Fossil Site (Tennessee). At both sites, a lacustrine environment was formed from sinkholes that preserve fossil assemblages including invertebrates, vertebrates, and plant remains. We reviewed the floristic record (micro and macrofossils) of each site to determine the late Neogene composition of the flora, its vertical stratification, and to provide insight into the changes associated with warmer and drier conditions in the eastern deciduous forest. The Pipe Creek Sinkhole flora when compared to extant pollen floras of the eastern US is nested within the Beach-Maple-Basswood forest type of Dyer; however, the Miocene forest is dominated by a pine-hickory or pine-hickory-cottonwood association. The Gray Fossil Site flora when compared to extant pollen floras of the eastern US is nested within the Mesophytic Forest and is dominated by an oak-hickory-pine assemblage. The Pipe Creek Flora and the Gray Fossil Site Flora lack the common sub story and understory taxa and are dominated by specific woody taxa and an array of herbaceous taxa that have high light requirements and indicate some disturbance. The lack of vertical forest structure indicates that at both sites, woodland to woodland savanna to prairie-like habitats may have prevailed. The common occurrence of charcoals in the lacustrine sediments indicates that fire was a frequent disturbance factor, which may have suppressed the development of a structured forest with a closed canopy at both localities. This was further exacerbated by the impact of large herbivores. Both fossil floras, despite changes in the vegetation composition and vertical stratification when compared to the extant indigenous deciduous forest, include the major elements from their respective extant mesophytic C3 floristic associations that currently exist at these locations, i.e. the Beech-Maple-Basswood (Pipe Creek Sinkhole) and the Hickory-Oak-Pine Mesophytic Forest (Gray Fossil Site). The Miocene-Pliocene climate, in comparison to the extant climate, affected the vegetation in eastern North America by the selective elimination of those taxa that could not tolerate the warmer and drier conditions; the concomitant increase in fire frequency and the impact of large herbivores further contributed to maintaining woodland/savanna communities at both localities.