The Occurrence of Pinus Massoniana Lambert (Pinaceae) from the Upper Miocene of Yunnan, SW China and Its Implications for Paleogeography and Paleoclimate
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Review of Palaeobotany and Palynology 215 (2015) 57–67 Contents lists available at ScienceDirect Review of Palaeobotany and Palynology journal homepage: www.elsevier.com/locate/revpalbo The occurrence of Pinus massoniana Lambert (Pinaceae) from the upper Miocene of Yunnan, SW China and its implications for paleogeography and paleoclimate Jian-Wei Zhang a,AshalataD'Rozariob,JonathanM.Adamsc, Xiao-Qing Liang a, Frédéric M.B. Jacques a, Tao Su a, Zhe-Kun Zhou a,⁎ a Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden (XTBG), Chinese Academy of Sciences, Mengla, Yunnan 666303, China b Department of Botany, Narasinha Dutt College, 129, Bellilious Road, Howrah 711101, India c The college of Natural Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Republic of Korea article info abstract Article history: A fossil seed cone and associated needles from the upper Miocene Wenshan flora, Yunnan Province, SW China are Received 11 August 2014 recognized as Pinus massoniana Lambert, which is an endemic conifer distributed mostly in southern, central and Received in revised form 12 November 2014 eastern parts of China. The comparisons of these fossils with the three extant variants in this species Accepted 15 November 2014 (P. massoniana var. shaxianensis Zhou, P. massoniana var. massoniana Lambert and P. massoniana var. hainanensis Available online 15 December 2014 Cheng et Fu) indicate that the fossils closely resemble P. massoniana var. hainanensis, which is a tropical montane thermophilic and hygrophilous plant restricted to Hainan Island in southern China. The present finding and a pre- Keywords: fi China vious report of Pinus premassoniana from the same age in southeastern China, which bears close af nities with Comparative morphology modern P. massoniana var. massoniana, suggest that the variation in this species arose earlier than was previously Fossil thought. Thus, the presence of P. massoniana var. hainanensis in the late Miocene Wenshan flora, Yunnan Province Late Miocene in southwestern China suggests (1) the subdifferentiation of P. massoniana began in the late Miocene or earlier; Phytogeography (2) the extant distribution of P. massoniana var. hainanensis might be derived from northern populations – the Pinus massoniana major distribution of extant P. massoniana – by southward expansion during Neogene or Quaternary climate changes; (3) disappearance of P. massoniana from southeastern Yunnan in southwestern China is probably relat- ed to the intensification of monsoon climate after the late Miocene. © 2014 Elsevier B.V. All rights reserved. 1. Introduction extant genus Pinus was classified into two subgenera, four sections and eleven subsections (Krupkin et al., 1996; Price et al., 1998; Gernandt The genus Pinus contains ca. 110 species of evergreen conifers with et al., 2005). Subgenus Pinus L. is distinguishable by two fibrovascular needlelike leaves. It is widespread in north temperate and north tropical bundles per needle with persistent fascicle sheaths, except for Pinus (mountainous) regions, with species found in North America, Central leiophylla Schiede ex Schlechtendal et Chamisso and Pinus lumholtzii America, Mexico, North Africa, West Indies, Eurasia (including one spe- Rob et Fernald, subgenus Strobus (D. Don) Lemon by a single fibrovascu- cies crossing the equator in Sumatra) and the Pacific Islands in Sumatra lar bundle per needle with deciduous fascicle sheaths, except for Pinus (Kral, 1993). In China, there are 39 species of Pinus (Fu et al., 1999). nelsonii Shaw, and the dorsal umbo position delineates subsection Strobus Pinus massoniana Lambert, a species with long slender needles of Loudon (terminal umbo) from all other pines. In this classification about 12–20 cm, is endemic in China and distributed mostly in south- (Gernandt et al., 2005), Pinus massoniana and 16 species found mainly ern, central and eastern parts of the nation, from a few hundred to from Eurasia and the Mediterranean region, were assigned to subsection 2000 m in moist river valleys to the dry mountain plateaus (Fu et al., Pinus sensu Gernandt, Geada López, Ortiz García et Liston in section Pinus 1999). Some populations of P. massoniana are also found on Taiwan sensu Gernandt, Geada López, Ortiz García et Liston of subgenus Pinus. (eastern China) and Hainan Island (southern China), but the paleogeo- Klaus (1980, 1989) has given another classification of Pinus based graphical evidence for this distribution pattern is lacking. on the location and morphological features of the mucro on the cone Based on the morphological features, such as vascular bundles in a scales. His approach matches the basic frame of existing classifica- needle, persistent fascicle sheaths, needle number per fascicle, needle tion systems (Klaus, 1980, 1989). He subdivided the subgenus resin ducts, cone scale, umbo prickle, seed wing and umbo position, the Pinus into two different groups: centromucronate with the mucro lo- cated in the center of the umbo and excentromucronate with the ⁎ Corresponding author. Tel./fax: +86 691 8715070. mucro situated above the transverse keel. The excentromucronate E-mail address: [email protected] (Z.-K. Zhou). species are further divided into four groups: denticulatomucronate http://dx.doi.org/10.1016/j.revpalbo.2014.11.006 0034-6667/© 2014 Elsevier B.V. All rights reserved. 58 J.-W. Zhang et al. / Review of Palaeobotany and Palynology 215 (2015) 57–67 with a long mucro positioned on the upper edge of the umbo field, Based on the geological survey (Zhang, 1976; Cai and Li, 2002), the perexcentromucronate with one short mucro positioned near the upper Neozoic sediments of the study area (Wenshan State located in SE Yun- edge of the umbo, erectoexcentromucronate with a long mucro arising nan Subregion of South China Region) is composed of Paleogene just a little above the transverse keel, and duplomucronate characterized Yanshan Group, Neogene Xiaolongtan Formation and Quaternary strata. by an excentric mucro and an additional central protuberance on the The molasses formation of Yanshan Group is composed of coarse clastic horizontal keel, a combination of a centro- and an excentromucronate rocks, heavy layer and lack fossils. Xiaolongtan Formation is the only umbo (Klaus, 1980, 1989). Centromucronate umbos are often present fluvio-lacustrine sediment in the study area, composed of laminated in the American pines and excentromucronate umbos occur in all the sedimentary sequences, and contains abundant animal and plant fossils. Eurasian pines (Klaus, 1989). Pinus massoniana and six other species Exposure of the Xiaolongtan Formation around Wenshan State is from eastern Asia, the Mediterranean and eastern North America, about 200–300 m thick, and generally divided into three members: which bear a short mucro situated near the upper edge of the umbo, the Upper Member (about 41.3 m thick, is missing in the present fossil are perexcentromucronate (Xing et al., 2010; Ding et al., 2013). locality, and distributed mostly in Maguan County in south of Wenshan The origin of genus Pinus is thought to be Early Cretaceous (Millar, State) is composed of thin layers (b0.1 m) of gray to white-gray marlite; 1998; Ryberg et al., 2012), whereas the estimated divergence times of the Middle Member (65.6 m thick here) consists of thin to medium the two subgenera range from the Late Cretaceous (Millar, 1998)to layers (b0.5 m) of gray-green to gray-yellow mudstone or fine sand- the middle Eocene (Miller, 1976). The earliest known Pinus fossils are stone, with interlayers of coal; and the Lower Member (27.1 m thick permineralized cones from the Wealden of Belgium (Alvin, 1960) and here) comprises medium layers (0.1–0.5 m) of gray to dark-gray con- Yorkshire (Ryberg et al., 2012), which show affinities to the subgenus glomerate or sandstone. The present fossils were collected from the Pinus (Miller, 1976; Willyard et al., 2007). The earliest fossils of the sub- Middle to Lower Members (92.7 m) of the formation which lie primarily genus Strobus are Late Cretaceous permineralized wood (Meijer, 2000), around Wenshan City (Zhang, 1976; Zheng et al., 1999; Fig. 2). The while the earliest leaves (Miller, 1973) or ovulate cones (Axelrod, 1986) Xiaolongtan Formation is late Miocene in age based on lithology, biolog- of the subgenus are reported from the middle Eocene. Hitherto, over 50 ic assemblage and regional comparisons (Dong, 1987; BGMRYP, 1996). fossil species of Pinus have been described in the world (Ding et al., It lies unconformably above the upper Oligocene Yanshan Group and is 2013). overlain unconformably by Quaternary strata (Zhang, 1976). In China, six fossil species have been described from Cenozoic sedi- The sedimentary sequences in Dashidong Village in Wenshan City ments. Among them, five (Pinus yunnanensis Franch, Pinus speciosa Li, yield abundant plant fossils, such as Quercus, Salix , Dryophyllum, Pinus prototabulaeformis Tao et Wang, Pinus prekesiya Xing, Liu et Zhou Ulmus, Zelkova, Ampelopsis, Populifolia, Glyptostrobus (Zhang, 1976), and Pinus premassoniana Ding et Sun) were established at least on the Ailanthus confucii Unger (Su et al, 2013), Bauhinia wenshanensis Meng basis of seed cones (Tao and Kong, 1973; NIGMR, 1982; Tao and Wang, et Zhou (Meng et al., 2014), Sequoia maguanensis Zhang et Zhou and 1983; Xing et al., 2010; Ding et al., 2013), and Pinus palaeopentaphylla Pinus,andfossilfish and insects (mosquitos, ants, etc.). Tanai et Onoe was based on needles (Guo and Zhang, 2002). The global climate