Parallel evolution of leaf morphology in gnetophytes
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ORIGINAL ARTICLE
Parallel evolution of leaf morphology in gnetophytes Yong Yang 1 & Longbiao Lin 2 & David K. Ferguson 3
Received: 15 January 2015 / Accepted: 9 July 2015 # Gesellschaft für Biologische Systematik 2015
Abstract In the present paper, an ephedroid macrofossil species from the Early Cretaceous Yixian Formation of western Liaoning of China is described as new to science: Ephedra multinervia Yang et Lin, sp. nov. This species has typical ephedroid morphology, e.g. the dichasial branching shoot system, swollen nodes, internodes having many fine longitudinal striations and opposite phyllotaxy. Ephedra multinervia has strap-shaped leaves with multiple dichotomizing veins and reduced female cones with a single pair of fertile bracts forming a cupule enclosing two inner seeds. Ephedra multinervia is similar to Ephedra archaeorhytidosperma Yang et al. and Ephedra hongtaoi Wang et Zheng in its reduced bi-ovulate female cone, but differs from the latter two species by the lengthy strap-like leaves bearing multiple parallel veins and its sessile female cones. A new evolutionary hypothesis of the gnetophytes is proposed based on a synthesis of reproductive morphology of macrofossils from the Early Cretaceous and modern representatives. A Chengia-like precursor might have given rise to the Gnetum-Welwitschia clade by diversification of leaf morphology and female reproductive
Electronic supplementary material The online version of this article (doi:10.1007/s13127-015-0226-6) contains supplementary material, which is available to authorized users. * Yong Yang [email protected] 1
State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, 20 Nanxincun, Xiangshan, Beijing 100093, China
2
China Railway Group Limited, 69 Fuxing Road, Beijing 100039, China
3
Department of Paleontology, University of Vienna, 1090 Vienna, Austria
organs. According to this new explanation, the Welwitschialike strap-like leaves with multiple parallel veins in E. multinervia result from convergence. Keywords China . Early Cretaceous . Ephedra . Evolution . Gnetophytes . Gnetum . Liaoning . Morphology . Palaeobotany . Welwitschia . Yixian Formation
Introduction The living gnetophytes encompass only three living genera, viz. Ephedra L., Gnetum L. and Welwitschia Hook. f. (Pearson 1929; Martens 1971; Gifford and Foster 1989; Price 1996). The genus Ephedra is represented by over 50 species widely distributed in the north temperate zone and high mountains of the Andes in South America (Stapf 1889; Cutler 1939; Florin 1933; Cheng and Fu 1978; Kubitzki 1990; Stevenson 1993; Price 1996; Fu et al. 1999). Gnetum contains 30 or more species ranging across the pantropical region (Kubitzki 1990; Price 1996; Hou et al. 2015). Welwitschia includes only one species endemic to southwestern Africa (Markgraf 1926; Pearson 1929; Martens 1971; Gifford and Foster 1989). The phylogeny of the three genera is well resolved; Ephedra is basal and sister to a clade encompassing Gnetum and Welwitschia (Fig
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