Research paper The genus Mahonia in the Miocene of Turkey: Taxonomy and biogeographic implications Tuncay H. Güner a , Thomas Denk b, ⁎ a Istanbul University, Faculty of Forestry, Department of Forest Botany, 34473 Bahçeköy, Istanbul, Turkey b Swedish Museum of Natural History, Department of Palaeobotany, Box 50007, 10405 Stockholm, Sweden abstract article info Article history: Received 27 October 2011 Received in revised form 21 February 2012 Accepted 22 February 2012 Available online 3 March 2012 Keywords: Mahonia Group Orientales Mahonia Group Occidentales Himalayan corridor North Atlantic land bridge Eurasia North America The genus Mahonia has a disjunct modern distribution with the New World Group Occidentales in northwestern North America and Central America and the mostly Old World Group Orientales in Central and Southeast Asia. Group Orientales has one species in North America. Morphologically, the two groups can be distinguished by two main patterns of leaf venation. Leaflets in the Group Orientales have a palmate-festooned brochidodromous venation and those of Group Occidentales usually have a pinnate-brochidodromous to (semi)craspedodromous venation, with some intermediate forms. In North America both Orientales and Occidentales can be traced from Eocene to Miocene strata. No unequivocal records of Mahonia are known from East Asia. A few Oligocene to Pleistocene fossils from Europe can be assigned to Group Orientales and to the section Horridae Fedde of Group Occidentales. Here we report two new species of Mahonia from the Miocene of Turkey, which clearly fall within the morphological range of the Group Orientales. One species, also found in the Oligocene–Miocene of western North America, is quite similar to Himalayan and East and Southeast Asian modern species. The other resembles the single modern North American member of Group Orientales. The high diversity of Mahonia in Europe and Asia Minor from the Oligocene onwards includes members of at least four lineages. The close relationships of these fossils with contemporary North American species suggest that the genus had reached western Eurasia from North America via the North Atlantic during or prior to the Oligocene. Colonization of Central and East Asia may have occurred from western Eurasia or North America, or from both directions. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The genus Mahonia Nuttall (Berberidaceae, Ranunculales) is a genus of shrubs and small trees with an American–East Asian disjunct modern distribution. Ahrendt (1961), in his monograph recognized about 130 species, which he subdivided into two groups, the largely Old World Group Orientales (including one species from North America) and the New World Group Occidentales, both of which consisted of about the same number of species. Members of the Group Orientales ex- hibit a centre of distribution in southwestern China (Yunnan, Sichuan), Burma, Bhutan, Nepal, northeastern India, and extending westwards to the western Himalayas. A few species occur in southern India, Vietnam, Taiwan, Sumatra, and the Philippines and a single species is native to western North America (Ahrendt, 1961). The Group Occidentales dis- tributes in northwestern and Central America. The species of Group Occidentales are ecologically different from the Old World species. While the New World taxa are commonly adapted to summer-dry climates and open landscapes, often growing on rocky substrates (Flora of North America Editorial Committee, 1997), those of the Old World are typically forming the undergrowth in evergreen broad- leaved forests, temperate rain forests, and temperate mixed broad- leaved deciduous and evergreen forests, and occur along rivers and in open disturbed areas and along forest edges (Flora of China Editorial Committee, 2011). Based on a molecular phylogenetic study of ITS data, Kim et al. (2004) distinguished three main clades among modern Mahonia, one corresponding to the Group Orientales, and two comprising the members of the Group Occidentales (Fig. 1). Mahonia has a rich fossil record in North America dating back to the Eocene (e.g., MacGinitie, 1953; Chaney and Axelrod, 1959; Axelrod, 1966, 1987). Although absent from western Eurasia today, a few fossils have been reported from the Cenozoic of Europe that unam- biguously belong to Mahonia (e.g. Takhtajan, 1974, Miocene of Abkhasia and Moldavia; Kvaček et al., 2011, Miocene of France). From East Asia, the genus has no reliable fossil record (cf. Manchester, 1999). In this paper, we describe two new species of Mahonia from the western part of Turkey. We evaluate the systematic affinities of these species to all the modern and to the North American and European fossil species of Mahonia. Furthermore, we discuss the biogeographic affini- ties of the species described here and of other Mahonia species from the Cenozoic of western Eurasia and implications for the historical bio- geography of the genus. Review of Palaeobotany and Palynology 175 (2012) 32–46 ⁎ Corresponding author. E-mail address: thomas.denk@nrm.se (T. Denk). 0034-6667/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.revpalbo.2012.02.005 Contents lists available at SciVerse ScienceDirect Review of Palaeobotany and Palynology journal homepage: www.elsevier.com/locate/revpalbo