Special issue on Ecology, evolution, and conservation of plants in China: Introduction and some considerations

Special iSSue on Ecology, Evolution, and consErvation of plants in china: introduction and Some conSiderationS.— China has one of the world’s richest floras with around 33,000 vascular plants, of which up to 17,000 are endemic. Besides these astonishing figures, the Chinese flora is very interesting from the point of view of evolution, as it shows a strong relictual character with some truly “living fossils” such as Ginkgo biloba or Metasequoia glyptostroboides. At the same time, China probably harbours the most important ‘‘evolutionary front’’ of the world’s temperate flora, the Hengduan Mountains. Unfortunately, the flora of China also includes a high number of threatened species (with nearly 4000), mostly due to the destruction of natural habitats and the over-exploitation of natural resources. This special issue, which corresponds to volume 34 of Collectanea Botanica, is aimed to contribute to the knowledge of Chinese flora through a series of contributions (seven full-length articles and one short note) spanning several topics such as biogeography, conservation, demography, ecology, evolution, and plant-animal interactions.

China is one of the world's richest countries in terms of plant diversity, only behind Brazil and Colombia.The estimated number of vascular plant species is about 33,000, with ~30,000 angiosperms, 200-250 gymnosperms, and 2100-2600 pteridophytes.Furthermore, approximately 2200-3000 bryophytes can be found in China (lópez-Pujol et al., 2006;Huang et al., 2015a;Wang et al., 2015b).More relevant are, nevertheless, the rates of endemism of Chinese flora: some 17,000 higher plants (i.e. over 50% of the total) are endemic to China (Wang et al., 2015b).At the generic level, about 250 genera are endemic, and, at the family level, several families are endemic (Eucommiaceae and Ginkgoaceae) or nearly endemic (e.g.Cercidiphyllaceae, Circaeasteraceae, Rhoipteleaceae, Tetracentraceae, and Trochodendraceae; Huang et al., 2015a).This wealth of species diversity and endemism is attributable to a series of physical and biotic factors, including: (1) a large country's area (about 9.6 million km 2 ); (2) a complex and extended geological history, with many tectonic events (including the collision of the Indian subcontinent at the Eocene); (3) an unbroken connectivity between tropical, subtropical, temperate and boreal forests; (4) a large proportion of tropical and subtropical habitats; (5) the close connection of China to tropical regions of Southeast Asia; (6) a highly rugged and dissected topography (especially in southern China); and (7) reduced extinction rates during the late Cenozoic global cooling (Axelrod et al., 1996;Qian & ricklefs, 1999;Qian, 2002;lópez-Pujol et al., 2011a).The main centres of species richness and endemism are highly coincident in China, and are almost exclusively located in the mountainous regions of central, southern and southwestern provinces (Fig. 1; Tang et al., 2006;lópez-Pujol et al., 2011a;Wang et al., 2011;Huang et al., 2012;Yang et al., 2013).
Besides the high taxonomic richness and exceptional rates of endemism, one of the main features of Chinese vascular flora is its ancient origin.China has a disproportionately large number of species belonging to the early diverged groups with ancient fossils; for example, the number of the pteridophytes and the gymnosperms are three times and almost two times larger in China than in the United States, respectively (Qian & ricklefs, 1999), a country with a similar land area and a comparable floristic richness and composition until the Middle Miocene ca.14-15 Ma (Axelrod et al., 1996).likewise, there is also an overrepresentation of the basal groups of angiosperms, such as the magnolids and ranunculids within the Chinese flora (Qian & ricklefs, 1999;Qian, 2001).other empirical data supporting the antiquity of Chinese flora are the Tertiary origin of most of the ca.1400 Asian endemic genera present in China (Qian et al., 2006), most of the ca.250 Chinese endemic genera (Ying et al., 1993;Wu et al., 2007), and ca.40% of the species belonging to the Chinese endemic genera (lópez-Pujol et al., 2011a).Many lineages that were widely distributed along the northern Hemisphere at the Miocene are still persisting in China, thanks to much lower extinction rates (Manchester et al., 2009).Conspicuous examples include Cathaya argyrophylla, Eucommia ulmoides, Ginkgo biloba, Glyptostrobus pensilis, Metasequoia glyptostroboides (Fig. 2), and Taiwania cryptomerioides.notably, most of these palaeoendemic taxa tend to occur in central, south-central, and southeastern China (Fig. 1), regions that have generally enjoyed relative tectonic stability since the late Tertiary or earlier (Hsü, 1983).At the same time, China harbours what is perhaps the largest "evolutionary front" of the world's temperate flora, the Qinghai-Tibet Plateau (QTP), especially its eastern fringe (the Hengduan Mountains; Fig. 1).The continuous uplifts of the QTP, in particular the recent uplifts since the late Pliocene, may have created a vast array of new habitats across wide elevational ranges (up to 5000 m), therefore stimulating rapid plant diversification and speciation (Fig. 2), including allopatric speciation, hybrid speciation and explosive radiations (liu et al., 2014;Wen et al., 2014;Favre et al., 2015;Hugues & Atchison, 2015).Hengduan mountains have been internationally identified as one of the world's biodiversity hotspots, with around 12,000 plant species, of which ~3500 are endemic (Myers et al., 2000).Some alpine genera have their centres of distribution here, a result of the abovementioned rapid radiations; examples include Rhododendron (276 out of ~1000 species of this genus around the world are present in the Hengduan Mountains), Pedicularis (233 out of ~600), Primula (143 out of ~500), Gentiana (154 out of ~360), Saussurea (119 out of ~415), or Aconitum (108 out of ~400) (zhang et al., 2009).
regrettably, the flora of China also stands out for the high number of threatened species, due to a series of combined factors mainly related with the country's overpopulation, the economic growth [China has shown the fastest rate of GDP (gross domestic product) growth among the world's major economies, with an average of almost 10% since 1980; http://data.worldbank.org/], the large-scale destruction of natural habitats, the over-exploitation of natural resources, and, on a lesser scale, the introduction of exotic species (although the lists of invasive and naturalized plant species have increased several-fold in just two decades; Fig. 3).At the beginning of the 2000s, it was estimated that at least 200 plant The code numbers for the hotspots correspond to those in the table below the map.relative occurrences for each type of plant species (+++, high occurrence; ++, intermediate occurrence; +, low occurrence) for each hotspot have been inferred after taking into account relevant literature (e.g.Ying et al., 1993;Wang & zhang, 1994;Ying, 2001;Tang et al., 2006;zhang & Ma, 2008;li et al., 2009;lópez-Pujol et al., 2011a;Wang et al., 2011;Huang et al., 2012;Yang et al., 2013).).The number of threatened plant species in China is, thus, slightly lower than the "classical" estimations of 4000-5000 (Wang, 1992;lópez-Pujol et al., 2006;Huang & oldfield, 2015), although it should be taken into account that more than 4000 taxa were listed as "Data Deficient" (DD) in the 2013 red list: an important fraction of these 4000 taxa, once a better knowledge is achieved, could be transferred to any of the threatened categories.Endangered species tend to be concentrated in the southern part of the country (zhang & Ma, 2008), thus showing high congruence with both centres of species richness and endemism (Fig. 1).
Despite the unquestionable interest, the study of the Chinese flora has been systematically neglected by south European botanists, and particularly by the Spanish ones.These latter have traditionally been more concerned with the flora of the new World.The discovery and further colonization of most of   (xinhua, 2015).Construction of transportation corridors such as railways do not only cause habitat fragmentation (and the associated edge-effects) but also the spread and establishment of non-native species (Andrews, 1990;Hansen & Clevenger, 2005).Photograph: J. lópez-Pujol.
the Americas by the Spaniards was followed by the study of their flora (e.g.Álvarez, 1993;De Vos, 2007), which has continued to the present.A variation of this sort of "colonial botany" (cf.Schiebinger & Swan, 2005) was behind bringing many Chinese plants to the West (including many ornamental plants such as azaleas, lilies, and magnolias) by European missionaries following the opium Wars (mid-19th century).Today, many plants are named for some of these "priests-botanists" (the most illustrious are probably J. M. Delavay, A. David, and P. G. Farges; see Kilpatrick, 2014).During late 19 th -early 20 th century, the European missionaries were gradually replaced mainly by British/Irish (such as G. Forrest, A. Henry, F. Kingdon-Ward, and E. This special issue of Collectanea Botanica, which corresponds to volume 34, has been launched not only for contributing to the knowledge of Chinese flora but also as an effort to increase the collaboration between Spanish and Chinese botanists, which remains, in spite of the pioneering efforts of the authors of the present note, virtually nil.This is not an isolated case, unfortunately, and certainly reflects the narrow-mindedness of the Spanish science system.The last official report on the Spanish scientific activity (FECYT, 2014) placed China, which is already the second-largest producer of research papers in the world (after the United States), "only" the 24 th in the rank of scientific collaborations between Spain and a third country (for example, behind Greece, Poland, and Chile).
This special issue is composed by eight articles (seven full-length articles and one short note) addressing several topics such as biogeography, conservation, demography, ecology, evolution, and plant-animal relations.Three of the contributions, those of liao & ren (2015), ren (2015), and Hu et al. (2015) are centred on some of the main hotspots of Chinese flora (Fig. 1).liao & ren (2015) explored the distribution patterns of long-lived individuals (≥100 years old) of several relict species (Cyclocarya paliurus, Ginkgo biloba, Liriodendron chinense, Pinus massoniana, Podocarpus macrophyllus, and Taxus chinensis) in the areas surrounding Fanjinshan nature reserve, located in the central China Mountains hotspot (probably the most important in China in terms of relict species; lópez- Pujol & ren, 2010;lópez-Pujol et al., 2011b).The authors conclude that, as reported in other studies (e.g.Hu et al., 2011;Gao et al., 2013), local protection due to traditional beliefs would have also played a role in addition to the existence of long-term stable habitats (see also Huang et al., 2015b).ren (2015) focused in another biodiversity hotspot, SE Yunnan-SW Guizhou-SW Guangxi (Fig. 1).He used distributional data of ca. 30 species belonging to the genus Hiptage to find that this region is a major diversification centre of this Asian endemic genus.Since other studies reported similar results for other tropical families including Gesneriaceae and Begoniaceae (li & Wang, 2004;Wei et al., 2004;Hou et al., 2010), it does not seem unreasonable to define this area (which is dominated by highly-fragmented limestone landscapes) as the "evolutionary front of the tropical plants in China" (ren, 2015: 9).Hainan is also one of the main hotspots of plant diversity in China (Fig. 1), and it is the subject of the studied carried out by Hu et al. (2015).The authors analysed the diversity and the patterns of distribution of the orchidaceae [the fourth largest family in China in number of species, but the first regarding the number of endangered species (ca.670 are included in any of the threatened categories; MEP-CAS, 2013)] in Hainan Island, identifying over 300 species (with ~10% of them endemic) that mainly occur on the southern part of the island.Hu et al. (2015) also revised the threats and the current conservation status of Hainan's orchids, and proposed future directions for research and management.
Although not strictly focused on the Chinese biodiversity hotspots, two additional papers within this special issue deal with biogeographical and ecological aspects within the topographically-complex, floristically-rich subtropical China.Tang (2015) presented an exhaustive analysis of the geographic distribution patterns of subtropical evergreen broad-leaved forests (EBlFs) in southwestern China (Guizhou, Sichuan, and Yunnan provinces plus Chongqing Municipality).In addition to comprehensively review the EBlFs in terms of forest types, species composition, and their distributions along latitudinal, longitudinal, and altitudinal gradients (which are magnificently illustrated), the author compared them with those of eastern China (with a special emphasis on Taiwan Island).Wang et al. (2015a) focused, instead, on aquatic habitats, and used traditional vegetation surveying methods to assess the richness of plant species and communities in Poyang lake.This lake, the largest one in China, has gained notoriety for the dam that has been planned to stabilize its water level (due to a series of droughts in recent years), causing serious concerns among biologists and conservationists (li, 2009).Wang et al. (2015a) identified over 500 plant species (as a catalogue in a separate appendix) as well as eight dominant plant communities, confirming the lake's wetland as a regional hotspot. liu et al. (2015) presented the state-of-the-art in the interactions between leaf miners (those insects whose larvae live in and eat the leaf tissue of plants) and their host plants.The authors first reviewed the leaf-mining patterns on plant leaves (i.e. the diversity of leaf mine shapes and depths).next, they addressed impacts in leaf morphology (e.g.asymmetry, presence of holes and cracks), leaf chemistry (e.g.production of secondary metabolites, formation of callus tissue), plant physiology (typically, a reduction of the photosynthetic capability of the leaf), and plant growth and production (e.g. earlier fall of the leaves, lower plant height, smaller leave size, lower number of leaves, reduction in fruit set).The authors further summarized the studies of leaf miners carried out in China.A further paper in this special issue is a mini-review of the main results of almost one-decade research carried by H. F. Wang and his collaborators on urban vegetation and plant diversity in Beijing, the capital of China.In their mini-review, Wang & lópez-Pujol (2015) first presented the main results of a study that employed urban structural units (USUs, that were defined based on urban land use and land cover) to explore urban ecological patterns and their relation with socio-economic factors.At the species level instead of landscape level, the authors reported the results of a systematic investigation on the plant species richness and density and the main socio-economic factors affecting them.They also summarized the naturalized and invasive flora in the whole municipality.This special issue was closed by a short note dealing with a growing menace for plant diversity in China: the plant invasions.Wang et al. (2015c) reported the first occurrence of Crassula ovata, the jade plant, in China, and warned about the potential for naturalization of this plant, as it is widely cultivated (at least in Sichuan, the province where it has been observed).
species had become extinct since the 1950s(zhang  et al., 2000), and new species have been added to this "black" list since then (seeMEP-CAS, 2013).Many more species are in an extreme situation of risk, with population sizes of fewer that one hundred individuals and occurring in just one or very few populations (e.g.lópez-Pujol & zhang, 2009; lópez-Pujol, 2010; ren et al, 2012; Ma et al., 2013); examples of these species in the brink of extinction [called sometimes as "Extremely narrow Endemics" (EnE) or "Plant Species with Extremely Small Populations" (PSESP); cf.lópez-Pujol et al., 2013; Ma et al., 2013] include Abies beshanzuensis var.beshanzuensis (from which only three individuals are remaining in the wild), Acer yangbiense (four individuals), and Carpinus putoensis (only one individual).According to the China Red List of Higher Plants (中国生物多样性红色名录-高等植物卷), published in late 2013, 3650 vascular plant taxa were regarded as threatened (Cr, En, or VU) following the 2001 IUCn criteria among the ~33,000 evaluated taxa (MEP-CAS, 2013

Figure 2 .
Figure 2. (A), type tree of Metasequoia glyptostroboides at Moudao Town (Hubei Province).This truly "living fossil" is a remnant of the Tertiary termophilous flora that once spanned most of the northern Hemisphere (the "boreotropical flora";Kubitzki & Krutzsch, 1996).Photograph: Q. leng; (B), individual of Meconopsis integrifolia at Diqing Tibetan Autonomous Prefecture, nW Yunnan; this is one of the flagship species of the Qinghai-Tibetan Plateau, and its speciation probably occurred during the rapid uplift of the plateau at Pliocene-early Quaternary(Yang et al., 2012).Photograph: J. lópez-Pujol.

Figure 3 .
Figure 3. Construction of the Chengdu-lanzhou high-speed railway.May 2015, Aba Prefecture, Sichuan.The first line of highspeed railway was completed in 2007, and the network reached 16,000 km at the end of 2014(xinhua, 2015).Construction of transportation corridors such as railways do not only cause habitat fragmentation (and the associated edge-effects) but also the spread and establishment of non-native species(Andrews, 1990;Hansen & Clevenger, 2005).Photograph: J. lópez-Pujol.
H. Wilson), Austrian (H.von Handel-Mazzetti and J. rock), and russian plant explorers (E.Bretschneider and G. n.Potanin), as well as the "first generation" of Chinese botanists (e.g.W.-C. Cheng, r.-C.Ching, W.-P. Fang, and T.-T.Yü) (Hi & Watson, 2015).After the advent of the "open door" policy in China since late 1970s, collaboration between Chinese and foreign botanists (especially with the American ones) is increasing steadily.The recent completion of the Flora of China project (partly funded by the U.S. national Science Foundation) is probably the best example.