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Home , Li Jijun, Tibetan Plateau

Journal of (J. Biogeogr.) (2016) 43, 1479–1487

PERSPECTIVE Available data point to a 4-km-high Tibetan by 40 Ma, but 100 molecular-clock papers have linked supposed recent uplift to young node ages Susanne S. Renner*

Systematic Botany and Mycology, University ABSTRACT The aims of this study were to synthesize data on the of Munich (LMU), Menzingerstr. 67, 80638 of the Tibetan Plateau (TP), with a focus on its elevation since the collision Munich, Germany of the Eurasian and Indian plates, and to review the arguments in 100 phy- logeny-cum-biogeography papers that have linked young inferred divergence times to recent TP uplift phases. I surveyed the literature on the geological history of the TP, focusing on different types of data used to infer its past height. I also tabulated the supposed TP history (and supporting references) in papers since 1998. Since the early 1990s, evidence from tectonics, isotopes, fossils and climate simulations increasingly indicates that the TP has been 4– 5 km high since the mid-Eocene. The data also indicate that the Indian sum- mer , South-east Asian summer monsoon, and Central Asian winter monsoon arose at different times and are unrelated to Tibetan uplift. A growing number of studies by biologists, however, are linking node ages between 0.5 and 15 Ma to specific (author-dependent) uplift phases of the TP citing geological papers that are outdated or miscited. Biogeography of the TP thus currently appears to be in a self-created bubble that encloses hundreds of authors and referees. Our understanding of the biogeography of requires up-to-date interpretation of its geological history and more fieldwork on local ecological habitat diversity, the plateau’s history during the Pleistocene and the distribution of possible refugia. *Correspondence: Susanne S. Renner, Systematic Botany and Mycology, University of Keywords Munich (LMU), Menzingerstr. 67, 80638 , , monsoon systems, Tibetan Fossils, Tibetan Plateau, Munich, Germany. uplift of Tibetan Plateau E-mail: [email protected]

that the recent, rapid uplift of the TP caused increased specia- INTRODUCTION tion and radiation in plants, animals and fungi. Over the past 20 years, the fields of biogeography and phylo- The TP (Fig. 1) extends for c. 2000 km from east to west, have blossomed due to molecular sequence data, and for up to nearly 800 km from north to south (Shackleton molecular clocks, improved data on geographical occurrences, & Chang, 1988); its surface area is c. 2.5 million km2, with an and better climate data and models. Studies in both fields fre- average height of 4000–5000 m and many peaks at 7000 and quently relate divergence-time estimates to palaeogeographical 8000 m. The plateau is characterized by dry climates and arid or climatic events, usually to infer abiotic factors causing spe- ecosystems although there are also rivers, lakes and high alti- cies formation or clade diversification (including extinction). tude bogs offering more humid habitats. Not surprisingly, Examples of such studies come from the biota of the Andes given its unique physical nature and size, the TP has numerous (e.g. Hoorn et al., 2010), Mount Kinabalu (Merckx et al., endemic plant and animal species. It has been a great challenge 2015), and the Panamanian land bridge (Bacon et al., 2015). for Earth scientists to explain how a c. 4.5 km high and ‘flat’ Next to the Panamanian land bridge, it is the Tibetan Plateau plateau can develop and how it relates to present-day crustal (TP) that in the past 17 years has received most attention from movements, earthquake activity, and climate. biogeographers (see Appendix S1 in Supporting Information Here, I summarize current views on the geological history of lists almost 100 studies). The conclusion from these studies is the TP for biologists, focusing on the different types of data

ª 2016 John Wiley & Sons Ltd http://wileyonlinelibrary.com/journal/jbi 1479 doi:10.1111/jbi.12755 S. S. Renner used to infer its past uplift or sinking and on evidence of recent and/or rapid uplift phases. The latter question was sug- 50° N gested by a large number of studies (see Appendix S1) that link Miocene, Pliocene and/or Pleistocene organismal radiations (usually specific nodes in molecular clock-dated phylogenies) to precise uplift phases of the plateau. If biogeography is to 30° N Tibetan Plateau stay relevant as a science it is important that we place species or biota in up-to-date geological contexts (Hoorn et al., 2010; Bacon et al., 2015; Merckx et al., 2015), and as the TP is the world’s largest and highest plateau, understanding its orogeny and the evolution of biota has intrinsic interest. Data on the 10° N Indian Indian Summer Mansoon Ocean uplift of the TP and the effects it may or may not have had on East Asian Summer Mansoon East Asian Winter Mansoon the origin of the Asian monsoon systems (Fig. 2) have not 0° been reviewed for non-geologists. Favre et al. (2015) made a 60° E 90° E 120° E 150° E start by bringing together some of the literature, but did not Figure 2 The modern Asian monsoon systems, modified with address (1) the strength of the evidence and (2) the historic permission from Zhang et al. (2012). origin of the contrasting views held by the majority of phyloge- neticists/biogeographers and the majority of Earth scientists. I end with suggestions for why the numerous young (post-Mio- Huang et al., 2015). Non-Chinese Earth scientists since cene) plant and animal clades endemic or partly endemic to (minimally) the early 1990s also hold that the TP had the TP might have nothing to do with any recent geological achieved an elevation of at least 3000 m between 45 and uplift. 30 Ma (Dewey et al., 1989: p. 727: ‘Tibet was thickened and elevated to about 3 km by a northward progression of short- ening between about 45 and 30 Ma in a regime of roughly THE UPLIFT HISTORY OF THE TIBETAN north–south plane strain.’), followed by an equilibrium of PLATEAU uplifting, faulting, and (Shackleton & Chang, 1988; Dewey et al., 1989; Tremblay et al., 2015). Shackleton and Evidence from tectonic models, geological data, Chang include a critique of the views of Chinese Earth scien- magnetostratigraphy and isotopes in ancient soils tists who, of course, were working in relative isolation before and water 1978 (cf. Origin of Chinese hypotheses on a young Tibetan Geophysical studies since the early 1990s, principally of mar- uplift and its ‘control’ of the monsoon systems). ine magnetic anomalies, resulted in the now generally Stable isotope dating of mica from the Thakkola Graben accepted estimate for the timing of India’s northward pro- (Fig. 1 and below), the largest N–S graben in north-central gression at 55–57 million years ago (Ma), with 52 Ma the , to 14 Ma implies that east–west extension developed best estimate for the cessation of marine sedimentation at well before then (Coleman & Hodges, 1995, p. 49: ‘well the northern margin of the Indian plate (Rowley, 1996; before Late Miocene time’). Similarly, isotope dating of vol- canic ashes to 40, 30, and 20 Ma (Chung et al., 1998) sug- gests that the TP underwent two main stages, one beginning at 40 Ma in the southern and a younger one begin- ning 20 Ma in the western , prompting Ruddiman (1998: p. 724, commentary on Chung et al.) to ask, ‘Now the question is whether further exploration of Tibet will find evidence of even earlier uplift, especially during the cooling between 55 and 40 Myr ago’. Volcanic ashes, however, may not be a good indicator of plateau height. Tectonic models in the early 1990s assumed an uplift of the TP beginning at 20 Ma, with the plateau reaching its greatest height by 8 Ma (Harrison et al., 1992) and collaps- ing since (Edwards & Harrison, 1997). These early models were soon doubted (Tapponnier et al., 2001; Rowley & Cur- rie, 2006) and of course, models per se do not provide infor- mation on elevation, but need to be constrained with Figure 1 Tibetan Plateau with sites discussed in the text proxies. Such proxies come from micro- or macrofossils or numbered: 1 = Lunpola, 2 = Namling, 3 = Thakkhola graben, from isotope ratios in ancient soils and water that are used 4 = Gyirong, 5 = Kunlun Pass, 6 = Nima, 7 = Zhada (Zanda) to infer the altitude in which particular microbes, plants or Basin, 8 = Xoh Xil. Image Landsat. animals may have lived (Harris, 2006 for a review). Given

1480 Journal of Biogeography 43, 1479–1487 ª 2016 John Wiley & Sons Ltd Old Tibetan Plateau ignored by 100 biogeography papers the immense size and time-depth of the plateau, the chal- 40 Ma slightly higher than at 20 and 0 Ma, in agreement lenge is obvious. with an assumed gradual collapse of the plateau (for exam- Tapponnier et al.’s (2001) tectonic model assumed strike- ple, Edwards & Harrison 1997). The Himalayan range in slip faulting beginning about ‘15 Ma after the onset of conti- Wang et al.’s scheme appears after 20 Ma, and it is thought nental impact’ (p. 1673; italics mine). Their map of the TP that most of the uplift of the Himalayas, , Pamir, shows its southern region as of Eocene age, the centre as Kunlun, and occurred 21–13 Ma (Searle, 2011). ‘Oligocene-Miocene?’, and the northern as Recent palaeomagnetic data suggest that the terrane ‘Pliocene-Quarternary’. Constraints from the interior of the was high before the collision of India with (Lippert TP were not yet available, hence the question mark. Time et al., 2014; Weller et al., 2015; Fig. 3). constraints for the south came from Garzione et al. (2000) who found shifts in d13Cpm values in palaeosol carbonate The Tibetan Plateau, climate simulations and the and plant material in the above-mentioned Thakkhola Gra- origin of the three Asian monsoon systems ben, indicating that by 11 Ma, that graben had reached heights between 4500 and 5900 m. Oxygen-isotope dating The relationships between TP uplift and the establishment of from the centre of the TP, from the Lunpola and Nima the Asian monsoon systems (Fig. 2) have long been a focus basins (Fig. 1), further indicates that these basins were at ele- of Earth scientists and climatologists (Molnar et al., 2010 for vations of 4–4.6 km for at least 35 Myr (Lunpola) or 26 Ma a review). Especially important was a climate simulation (Nima), implying initial uplift 40–50 Ma (Rowley & Currie, described in 2001 that used changes in accumulation 2006; DeCelles et al., 2007). For Lunpola, there are also U/ north-west of the TP and in sediments from the Indian and Pb zircon dates indicating it was at > 4 km in the late Oligo- Pacific oceans as its input and ‘highly idealized stages of ele- cene (He et al., 2012). The and the Qaidam vation history for the Himalayan-Tibetan region’ (An et al., Basin (Fig. 1) also were at high elevations back to at least 2001, p. 63). The simulation suggested that a possible step- the Oligocene (Wang et al., 2008 and Saylor et al., 2009 for wise uplift together with Pleistocene summaries). Isotope-based palaeosol dates indicate high alti- glaciations would fit with Indian and East Asian monsoon tudes by 15 Ma even for the northern TP (Quade et al., initiation as recently as 9–8 Ma. Many biogeographers now 2011: Xoh Xil Basin, Fig. 1), leading the latter authors to cite this (poorly constrained) simulation as having proven a conclude (p. 111) that, ‘...there is no evidence that the ele- phased uplift of the TP starting at 9–8 Ma (see Appendix S1 vation of the Tibetan Plateau has changed by more than ca. list at least 37 papers citing it in this way, usually along with 500 to 1000 m a.s.l. since the middle Eocene’ and that ‘evi- Harrison et al., 1992). dence from these soils suggests that much of Tibet attained Since 2001, the assumed links between Tibetan uplift and its modern elevation by the mid-Eocene’ (l.c., p. 77). both types of proxies in An et al.’s simulation have become The aridification of the TP has been inferred from the dis- doubtful, and the simulation was also immediately criticized appearance of playa lake deposits in the north-eastern part for the poor time constraints on its components, namely of the plateau, occurring precisely at the time of the global the uplift of the Himalayas and of the TP (which are not Eocene–Oligocene (34 Ma) climate transition (Dupont-Nivet the same; previous section), the time(s) of intensification of et al., 2007). While a possible TP uplift at that time could the monsoon systems, and their relation to wind and rain- have contributed to aridification, these authors see this as fall patterns, in turn affecting loess deposition in Qinan in unlikely. Instead, they attribute the onset of an arid climate NW and sedimentation in the (Gupta to the global cooling around 34 Ma, due to the opening of a et al., 2004: Table 1 summarizes the large uncertainty in sea passage around Antarctica, glaciation of Antarctica and the time estimates for these model components). An the resulting dramatic reduction in World sea levels, which increase in sedimentation rates in the Indian Ocean after led to the retreat of the Paratethys, a northern arm of the 33 Ma was initially interpreted as indicating surface uplift Tethys, also called Turan Sea, and the drying of the Tarim of the TP, the source of the SE Asian rivers, coupled with Basin (Figs 1 & 3). The Paratethys retreat is dated to intensification of the Indian summer monsoon (Clift, between 47 and 37 Ma (DeConto & Pollard, 2003; Bosboom 2006). However, sediment flux peaked in the early–middle et al., 2014). In short, the uplift of the TP is not the only, or Miocene (24–11 Ma), when the TP was already high. More even most plausible, explanation of Oligocene/Miocene aridi- humid, warm climates in the early–middle Miocene corre- fication in . Instead, the westward Tethys retreat late with higher rainfall and faster erosion, followed by probably reduced the moisture load of Westerlies blowing drier climates after 14 Ma when Antarctic glaciation began into the Asian continental interior. (Clift, 2006). It is thus probably rainfall-dependent erosion Support for a 50 my-old TP is summarized by Royden that drove the sediment load during the Early and Middle et al. (2008), Wang et al. (2008), and Lippert et al. (2014) Miocene, not a sudden spike in TP uplift: ‘We discount who present data from magnetostratigraphy, sedimentology, tectonically driven rock uplift as a trigger for the faster ero- 40Ar/39Ar and fission-track studies, and isotope dating of sion...’ (Clift et al., 2015, p. 69). palaeosoils that all point to the central plateau having been Second, the aeolian sediments (loess) from basins north- high by 35–40 Ma. Wang et al.’s fig. 6 shows the TP at west of the TP, so important to the An et al. (2001) model,

Journal of Biogeography 43, 1479–1487 1481 ª 2016 John Wiley & Sons Ltd S. S. Renner

Siberian Sea

Shan Qilian Shan

ien Turan Sea T Tarim Kunlun Shan Basin M e di ter ran Lhasa-plano ean Vie Te tna th a m y malay s Tibetan Hi G rea ter In r d S o ia u t Ba m a L s at u es in ra q A se E ra r G bia re at er I ndia A fri In ca dia

Figure 3 Early Eocene palaeogeographical reconstruction of the Neotethyan region at the time of collision between the Tibetan Himalayan microcontinent and the southern margin of Asia. The elevated Lhasa-plano is the proto–Tibetan Plateau. Reproduced with permission from Lippert et al. (2014). are now thought proof that the Asian winter monsoon ex- the initial collision of greater India with , its changing isted by at least the early Miocene, 22 Ma (Guo et al., intensity not driven by tectonic drivers but by Milankovich– 2002), not that they first arose 9–8 Ma (An et al., 2001). Croll cyclicity (Srivastava et al., 2012; Shukla et al., 2014). Large source areas of dust and strong monsoon winds The East Asian summer monsoon (Fig. 2) also existed by at existed in the interior of Asia (Mongolia), and the ‘Miocene least the late Oligocene (Srivastava et al., 2012). sequences of Qinan do not show any obvious long-term An et al.’s (2001) climate simulation, which assumed a intensification of loess deposition between 22 and 6.2 Ma’ phased uplift of the TP from sedimentation rates north and (Guo et al., 2002, p. 162). Two intervals with higher dust south of the plateau (the latter marine), is thus no longer a accumulation at 15–13 and 8–7 Ma are now thought to suitable explanation of either the evolution of the Asian represent temporary instabilities in the dust source region. monsoon systems or the timing of TP uplift. Nevertheless, it Recent climate simulation further supports that the retreat continues to be cited by biogeographers as having shown the of the Paratethys Sea from Central Asia (cf. previous sec- onset of the Indian and East Asian monsoon at 9–8 Ma due tion and Fig. 3) would on its own have led to significant to the a phased uplift of the TP (see Appendix S1). aridification and intensification of the Asian winter mon- soon by redistribution of land-sea thermal contrasts and by Evidence from plant and animal macrofossils providing less moisture to the Asian interior to the east (Bosboom et al., 2014). Among the first to infer the palaeoaltitude of the TP from Palaeobotanical data (next section) from sites throughout plant macrofossils were Spicer et al. (2003), who analysed a China place the origin of the Asian winter monsoon to 15 Myr-old leaf flora from a site in the Namling basin (minimally) the latest Oligocene (Sun & Wang, 2005), while (Fig. 1). They used the correlation of leaf physiognomy the Indian monsoon system is much older than the Miocene with mean annual temperature and rainfall established by and probably existed as early as the early Eocene, soon after Jack Wolfe, a co-author on the study: The percentage of

1482 Journal of Biogeography 43, 1479–1487 ª 2016 John Wiley & Sons Ltd Old Tibetan Plateau ignored by 100 biogeography papers entire-margined leaves in living floras is linearly correlated only with water temperature, but also with an individual’s with the average yearly temperature, which in turn is affected age and the species’ egg size, nesting behaviour, and crowd- by altitude. Using this approach, Spicer et al. (2003) recon- ing (Coburn, 1986). Several North American cyprinids also structed the elevation of their site as 4.6 km with an error have an average vertebra number of just 34 (l.c.). range of around 1 km and concluded that the study region had been at its present height for at least 15 Ma (this con- ORIGIN OF CHINESE HYPOTHESES ON A clusion is even in the paper’s title Constant elevation of south- YOUNG TIBETAN UPLIFT AND ITS ‘CONTROL’ ern Tibet over the past 15 million years). Nevertheless, the OF THE MONSOON SYSTEMS paper has been cited as establishing TP uplift starting at 15 Ma (see Appendix S1 lists 26 studies citing it in this Before China opened itself to the outside world in 1978, Earth way). Sun et al. (2015) recently used fossil Berberis leaves scientists there had worked in relative isolation. After 1978, (distinctly spiny) from early–middle Miocene sediments of a scientific exchange and joint research expeditions to the TP site in northern Tibet at 4600 m to infer that that site began almost immediately, and it was then that ‘foreign uplifted by c. 2000 m since then. The study, however, has researchers ... challenged the viewpoint [of an extremely been severely critiqued because of its insufficient attention to young TP] and preferred a much earlier Tibetan Plateau uplift’ variation in leaf morphology and altitudinal ranges of Ber- ( & Fang, 1999: 2121–2122). The first author of this quote, beris species that do not allow the inference of a precise Li Jijun, was professor of geography at University. He palaeoaltitude from few fossil leaves (Denk, 2015). hypothesized that ‘the Highland was levelled twice and rose Animal macrofossils providing evidence on the palaeoalti- thrice during the late Cenozoic era, with the latest intense ris- tude of the TP are teeth and bones of late Miocene Hippar- ing commencing 3.6 m years ago, preceding through the Qing- ion (horse) faunas and Oligocene fish fossils (see Wang Tibet Movement (3.6 - 1.7 m years), the Kunhuang Movement et al., 2015 for a beautifully illustrated review of the Tibetan (1.2 - 0.6 m years) and the Republic Movement (0.15 m years) Cenozoic vertebrate record). Tooth enamel of herbivores until it reached its present height, accumulating 3,500 - 4,000 records the isotopic composition of their plant food, offset m’ [cited from his online page at the Chinese Academy of by biochemical fractionation of d14&, and it can thereby be Sciences (CAS) to which he was elected in 1991]. Li’s papers inferred if animals foraged largely in grass or broad-leaved and especially the two volumes he edited with Shi Yafeng (Li environments. The enamel of horse and bovid teeth from the et al., 1995 and Shi et al., 1998) are the most cited sources for Gyirong Basin (Fig. 1), Biru (), a ‘young Tibet’ in the almost 100 biological studies listed in and the Zanda Basin just north of the crest of the Himalayas Appendix S1. Shi Yafeng graduated in geography at Zhejiang (Zanda Basin is the for the Zhada Basin) con- University in 1942 and was elected to the CAS in 1980. He is tains evidence of both C3 and C4 plants (Wang et al., 2006; an expert on and is considered the father of Deng et al., 2011, 2012), but because C4 grasses do not research in China. Naturally, both scientists, Li and Shi, pub- occur above c. 3000 m, the authors inferred that at that time lished most their work in Chinese, and of their eight most the elevation of the Gyirong Basin perhaps was lower than cited papers (see Appendix S1) only a few have English 2900–3400 m and that its present elevation of 4200 m was abstracts. Nevertheless, one can study the papers’ illustrations attained after c. 7 Ma. From the Zanda enamel and bones, and literature lists, and based on this, they appear scientifically which are 4.6 Ma old, they infer an elevation comparable to isolated. today. Modern Tibetan ass (Equus ), as well as many A third extremely important contributor is , other large mammals, readily survive at elevations above an expert on Chinese loess soils and the researcher who ‘pro- 5000 m a.s.l., and many species forage over wide altitudinal posed the monsoon control hypothesis of East Asian envi- ranges (Wang et al., 2015), cautioning against overconfidence ronment variation’ (cited from his CAS web page; he became in palaeo-elevations from enamel. Also, carbon isotope anal- an Academician in 1991). The climate simulation by An yses of Zanda plant remains and molluscs ranging in age et al. (2001) has been cited 842x (Scopus at http://www.na- from 9.2 to 1 Ma indicate that over this period the cold and ture.com/nature/journal/v411/n6833/abs/411062a0.html, arid climate was ‘indistinguishable from modern conditions accessed 19 August 2015), and of the studies listed in there’ (Saylor et al., 2009, p. 1). Appendix S1, over a quarter cite this paper as having ‘shown’ A16–18 Ma cyprinid fish from the Lunpola Basin has 46– that the uplift of the TP occurred 9–8 Myr and 3.6–2.6 Ma 48 vertebrae as is typical of cool water cyprinids, while and caused the Asian monsoon systems. another fossil from the Nima basin, dated to 23.5–26 Ma, The many contributions by Li Jijun, Shi Yafeng, and An has 33 vertebrae, a low number more typical of warm water Zhisheng, their important role in the development of the cyprinids (Wang & , 2015). The already cited analyses of Earth sciences in China, and these researchers’ academic soil carbonates and zircon isotopes place both basins at 4.5– standing undoubtedly contributed to the ‘young TP’ view 5 km a.s.l. already by the late Oligocene (DeCelles et al., continuing to be cited by Chinese biologists and their Wes- 2007; He et al., 2012), implying that both fish probably lived tern collaborators although it is no longer held by Earth sci- in cool waters. Whether the number of vertebrae is a reliable entists and climate modellers; Sun & Wang (2005) and Liu temperature indicator is unclear because it correlates not & Dong (2013) summarize the views of a new generation of

Journal of Biogeography 43, 1479–1487 1483 ª 2016 John Wiley & Sons Ltd S. S. Renner

Chinese climate researchers, concluding that the monsoon MOLECULAR-CLOCK STUDIES THAT INTERPRET systems and TP uplift occurred asynchronously. BIOLOGICAL DIVERSIFICATION IN THE CONTEXT OF AN OLD (PRE-OLIGOCENE) AGE OF THE TIBETAN PLATEAU REVIEW OF PHYLOGENETIC, PHYLOGEOGRAPHICAL, AND I found five studies (four botanical, one zoological) that did BIOGEOGRAPHICAL STUDIES LINKING RECENT not assume recent plateau uplift, but instead suggested that (20–0.5 MA) DIVERSIFICATION TO (ASSUMED) their focal clades probably or definitely diversified when the RAPID UPLIFT OF THE TP plateau was already high. Thus, Yue et al. (2009, p. 412), for a genus of Brassicaceae, concluded that ‘One may speculate Appendix S1 lists 95 studies that have linked a supposed (very) that radiation of this clade was accelerated by post-Miocene recent uplift of the TP to young node ages (divergence times) uplift of the -Tibetan Plateau, a hypothesis that has inferred by molecular-clock dating or in a few cases coales- been raised numerous times in the literature, [...] However, cence dating. The table does not include studies that simply geological evidence for such uplift is mixed at best. Oxygen report the recent uplift as an established fact (e.g. Qu et al., isotope analyses suggest that current elevations in south-wes- 2013; Merckx et al., 2015). Where the same authors published tern Tibet have been maintained, or were perhaps even on the same topic twice, once in a more ‘international’ journal higher than present, since the late Miocene’ (Saylor et al., (usually with at least one non-China-based co-author), once 2009). Miao et al. (2011) in a study of Artemisia give an up- in a more ‘Chinese-audience-orientated’ journal, I have to-date summary of data – all suggesting that included only the more international publication (this applied the TP has been high since the Eocene – and conclude that to some eight studies). The studies were published in Molecu- it was the high cool habitats that provided the setting for the lar Phylogenetics and Evolution (31, see Appendix S1), Molecu- diversification of Tibetan Artemisia. A study of Delphinieae lar (13), PLoS One (8), Biological Journal of the Linnean found that the Tibetan Aconitum clade began diversifying Society (4), and Journal of Biogeography (4), and a range of more or less 7.8 Ma and concluded that this diversification other outlets including Nature Communications, Molecular could not be related to any rapid uplift because by that time Biology and Evolution, and the Proceedings of the National the TP had more or less its present elevation (Jabbour & Academy (USA). Papers linking young node ages to assumed Renner, 2012). Zhao et al. (2015) placed the diversification rapid TP uplift started appearing between 1998 and 2003, with of SE Asian Zingiberaceae in the context of the uplift of the rate accelerating since (see Appendix S1). Northern and the foothills of the Himalayas, where Most of the studies used average substitution rates to cali- their focal clades occur. They relate a c. 44 (29–65) Ma brate genetic distances (to obtain absolute time), some used divergence between a lowland genus and the common ances- fossils, a few coalescence dating, and four used (very recent) tor of two higher altitude genera to TP and Himalayan uplift uplift phases of the TP as constrains (see Appendix S1; they during the middle Eocene (strangely merging the TP and were published in 1998, 2009, 2010 and 2012 in Molecular Himalayas into one), and a more recent divergence at c. 32 Phylogenetics and Evolution and Molecular Ecology). One (18–50) Ma to an assumed second uplift of the Himalayan– study used the ‘uplift of the Isthmus of Panama’, set to TP (there is no such plateau) at the onset of the Oligocene 3.5 Ma, as constraint for the genetic distances in a Tibetan to the Eocene (c. 30–40 Ma). Lastly, P€ackert et al. (2015) clade (see Appendix S1). Except for these five studies, I see provide an overview of Tibetan passerine lineages that date no reason to doubt the calculated young divergence times back to the late Miocene and Pliocene and then place these for species or clades occurring on the TP (even cryptic spe- diversifications in an up-to-date geological context. cies are linked to the plateau’s uplift, Lu et al., 2014). The editor of this paper, however, pointed out that all these clock-based estimates could be erroneous and the clades CONCLUSIONS – THE ROLE OF PLEISTOCENE might be much older than their fossil-based minimum ages GLACIATIONS (M. Ebach, 15 December 2015). Available original data relevant to the uplift of the TP all The inferred node ages in the 100 studies cover every Myr point to the plateau having reached average heights of 4– interval between 20 and 0.5 Ma, and they concern plants, 5 km by 40 Ma, and even the Yunnan Plateau underwent its animals and fungi (see Appendix S1). The Earth science principal uplifting epoch during the Early Oligocene (Tap- studies most commonly cited as supporting a Miocene or ponnier et al., 2001: Fig. 2). Data supporting this come from Pliocene uplift by 2–3 km of the plateau are Harrison et al. isotope dating of micro- and macrofossils, isotope dating of (1992), An et al. (2001), Spicer et al. (2003), and the books minerals, inferences from fossil morphologies of plants and and publications by Li Jijun, Shi Yafeng and their students animals, indirect evidence from wind- or river-borne sedi- and colleagues. I have already described the data and conclu- ments to the south and north of the Plateau, and magne- sions of these five main sources in the previous sections. In tostratigraphy. Climate models today imply that initiation of short, these sources do not support what they are cited for, the three Asian monsoon systems (Fig. 2) was not due to TP and their stated conclusions are different from what they are uplift, although the Himalayan orogeny, mainly 21–13 Ma said to have said, often drastically so.

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(Searle, 2011), modified the Indian and East Asian summer fascinating. Its biota had many million years during which to monsoon systems. The precisely bracketed three uplift events adapt to high-altitude conditions, and it might be worth at 3.6–1.7, 1.1–0.6 and > 0.15 Ma of Li & Fang (1999 ff.) considering this as one explanation why lineages may have have never been demonstrated with sufficient accompanying survived extremely adverse Pleistocene conditions. data, but continue to be cited, albeit not always attributed to their source, Academician Li Jijun (see Appendix S1). I could ACKNOWLEDGEMENTS not trace the more rarely mentioned four uplift events at 25– 17, 15–13, 8–7, and 3.5–1.6 Ma of Wen et al. (2014; also see I thank Peter Lippert, Department of Geosciences, University Appendix S1) to a geological study. of Arizona, for guidance to the geological literature and many The c. 100 biogeographical/phylogenetic papers that have patient and content-rich emails; Zhang Dianxiang, Guangzhou invoked rapid and recent uplift of the TP were written by Botanical Garden, for sending me Shi et al.’s (1998) book; c. 400 researchers (see Appendix S1) and must have been Thomas Denk, Swedish Museum of Natural History, Depart- seen by c. 200 referees. Regardless of when precisely the TP ment of Palaeobiology, for critical assessment of literature on reached its average height of 4 km – a topic that doubtlessly fossils; and Ling-Yun Chen, Wuhan Botanical Garden, for help requires more work by Earth scientists, palaeontologists and with the literature search. I thank Martin P€ackert, Michael climate modellers – , it does not reflect well on our field that Heads and an anonymous referee for insightful comments. endlessly repeated statements about TP uplift and heights at such and such a time (always fitting one’s inferred node REFERENCES ages) have escaped checking for 15 years. A likely explanation for the young species divergences An, Z.S., Kutzbach, J.E., Prell, W.L. & Porter, S.C. (2001) inferred in so many studies (see Appendix S1) is that most Evolution of Asian and phased uplift of the species/populations living on Earth at any one time are Himalaya-Tibetan plateau since Late Miocene times. Nat- young. Similarly, Miocene and Pliocene ages of Tibetan ure, 411,62–66. clades found in dozens of studies probably reflect that most Bacon, C.D., Silvestro, D., Jaramillo, C., Smith, T.B., Chakra- clades on Earth ranked as sections, genera or subtribes are of bart, P. & Antonelli, A. (2015) Biological evidence Miocene or early Pliocene age. 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Evolutionary diversification of alpine ginger reflects the Srivastava, G., Spicer, R.A., Spicer, T.E.V., Yang, J., Kumar, early uplift of the Himalayan–Tibetan Plateau and rapid M., Mehrotra, R. & Mehrotra, N. (2012) Megaflora and extrusion of Indochina. Gondwana Research (in press). palaeoclimate of a Late Oligocene tropical delta, Makum Coalfield, Assam: evidence for the early development of SUPPORTING INFORMATION the South Asia Monsoon. , Palaeoclimatol- ogy, Palaeoecology, 342–343, 130–142. Additional Supporting Information may be found in the Sun, B., Wang, Y.-F., Li, C.-S., Yang, J., Li, J.-F., Li, Y.-L., Deng, T., online version of this article: Wang, S.-Q., Zhao, M., Spicer, R.A., Ferguson, D.K. & Mehro- Appendix S1 Molecular-phylogenetic studies (in chronolog- tra, R.C. (2015). Early Miocene elevation in northern Tibet esti- ical order) that have linked plant or animal clade radiation mated by palaeobotanical evidence. Nature Scientific Reports, 5, or population divergence to specific uplift phases of the 10379. Availabe at: www.nature.com/scientificreports/. Tibetan Plateau (TP). Sun, X.J. & Wang, P.X. (2005) How old is the Asian mon- soon system? Palaeobotanical records from China. Palaeo- BIOSKETCH geography, Palaeoclimatology, Palaeoecology, 222, 181–222. Tapponnier, P., Xu, Z.-Q., Roger, F., Meyer, B., Arnaud, N., Susanne S. Renner is a systematist and evolutionary biolo- Wittlinger, G. & Jingsui, Y. (2001) Oblique stepwise rise gist interested in the evolution of plants, plant animal/inter- 294 – and growth of the Tibet Plateau. Science, , 1671 1677. actions, plant mating systems and biogeography. Tremblay, M.M., Fox, M., Schmid, J.L., Tripathy-Lang, A., Wielicki, M.M., Harrison, T.M., Zeitler, P.K. & Shuster, D.L. (2015)ErosioninsouthernTibetshutdownat  10 Ma Editor: Malte Ebach

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