Plant diversity in Yunnan: Current status and future directions
Li-Shen Qiana,b,c, Jia-Hui Chena, Tao Denga, Hang Suna     
a. CAS Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, 650201, China;
b. University of Chinese Academy of Sciences, Beijing, 100049, China;
c. School of Life Science, Yunnan University, Kunming, 650091, China
Abstract: Yunnan, located in southwestern China, harbors more than 19, 000 higher plants, which represents the highest plant diversity in the country. However, plant diversity in Yunnan faces enormous threats today, including habitat destruction and fragmentation, environmental pollution, and over-exploitation of natural resources. Despite recent efforts to protect biodiversity, there are still thousands of threatened species, some of which have become extinct. We analyzed available data to gain a greater understanding of plant diversity and the status of plant conservation in Yunnan. We found that southern, southeastern, and northwestern Yunnan are hotspots of total species, endemic species, specimens, new species and threatened species, whereas southeastern Yunnan is a hotspot for plant species with extremely small populations. Moreover, we found that there are still conservation gaps and poorly protected areas in central, eastern, and northeastern Yunnan. We conclude that conservation of plant diversity in Yunnan requires modern field investigation, systematic research, the development of comprehensive databases, and government support. We recommend that conservationists pay more attention to building and improving functional protection systems and popularizing science.
Keywords: Biodiversity    Conservation status    Protection    Yunnan Province    Hotspot    
1. Introduction

Yunnan is located in southwestern China from 21°08'35''N to 29°15'03''N and 97°3104100E to 106°11'45''E, where it borders Guizhou, Guangxi, Sichuan and Tibet in China and the countries of Myanmar, Laos and Vietnam. Yunnan covers a total area of 394, 000 km2 (Yang et al., 2008) with terraced terrain and an average elevation of 2000 m (Cheng et al., 2019; Li et al., 2013). Yunnan has six river systems, as well as 11 major and 19 small plateau lakes (Wang and Dou, 1998; Yang and Li, 2010). The highest peak is Kawakarpo, Mt. Meili in NW Yunnan, with an elevation of 6740 m and the lowest point is in SE Yunnan at the Nanxi River, which is 76 m above sea level (Yang et al., 2008).

Yunnan's climate is dominated by a large elevational range and the seasonal alternation of the southwest and southeast monsoons, which cause a wet (May to October) and dry season (November to April) (Yang et al., 2008). The topographic configuration of Yunnan and its distinct dry and wet seasons are thought to have been critical to the development of biodiversity in this region, which is both a cradle and a museum of plant diversity.

Yunnan accounts for only 4.1% of the total land area of China, but contains more than half of all higher plants, or 19, 333 species, which belong to 3, 084 genera and 440 families. Furthermore, Yunnan harbors the most plant species endemic to China. To date, 160 nature reserves have been established in Yunnan (Yunnan Forestry and Grassland Bureau, 2016 ), and are classified into four levels: National, Provincial, Municipal and County. In 2018 , the Management Standard of Nature Reserves was implemented, providing a basis for assessment of standardized construction and management of these nature reserves. In the same year, the first local regulations to protect biodiversity in China, Regulations of Yunnan Province on Biodiversity Conservation, were issued. These regulations made Yunnan a pioneer of biodiversity conservation legislation in China (Ministry of Ecology and Environment of the People's Republic of China, 2018 ). Consequently, research on plant diversity, assessment, and conservation in Yunnan has attracted worldwide attention and emphasized the importance of protecting national biodiversity and biological resources (Bao et al., 1995; Ma, 2020; Yang et al., 2008).

In this work, our objectives are (1) to provide information on plant diversity and the status of plant conservation in Yunnan, (2) to evaluate the status of plant diversity surveys and research in Yunnan, and (3) to provide recommendations regarding future challenges to biodiversity in Yunnan.

2. Materials and methods

We integrated plant distribution data in Yunnan into a countylevel distribution database of all seed plants species, specimens, new species, threatened species, and Plant Species with Extremely Small Populations (PSESPs). The distributional data were derived from latest released catalogues, published articles and online herbarium database resources, including Flora of China, Flora of Yunnan, The Checklist of Biological Species from Yunnan (2016 ), Species Red List of Yunnan Province (2017) (http://bio360.kun.ac.cn/index/redlist), Program outline of saving and protecting the species of minimal population in Yunnan Province (http://lcj.yn.gov.cn/yunnanwz/pub/cms/2/8407/8415/8494/8497/92486.html), Annual Report of Yunnan Nature Reserve 2016 (http://lcj.yn.gov.cn/8415/8419/8660/8669/114841.html), NSII (http://www.nsii.org.cn), Kingdonia (http://kun.kingdonia.org/) and Chinese Virtual Herbarium (CVH) (http://www.cvh.ac.cn/). We also analyzed the numbers, locations, and areas of nature reserves in Yunnan. Distribution maps were created by ArcGIS 10.4.1.

3. Results and discussion 3.1. Plant diversity in Yunnan 3.1.1. The composition of plant diversity

Yunnan harbors more than half of the plant species in China (Fig. 1A). The Checklist of Biological Species from Yunnan (2016 ) recorded 19, 333 higher plant species belonging to 3, 084 genera and 440 families (Fig. 1B) (Sun and Gao, 2016). Forty-three main families (>100 species) account for more than 77% (11, 662 species) of all angiosperm species in Yunnan, and nearly half of all angiosperms in Yunnan are represented by three families: Orchidaceae (995 sp.), Poaceae (936 sp.), Asteraceae (914 sp.) (Table 1). Thirteen main genera comprise over 100 species, including Rhododendron (349 species, 54% of China) and Pedicularis (196 species, 59% of China) (Table 1). However, most of the angiosperm genera in Yunnan (1989/2361) have fewer than 10 species.

Fig. 1 (A) Number of plant species in Yunnan based on different criteria. (B) Updated composition of plant diversity in Yunnan.

Table 1 Diversity composition of (A) three climate zones, (B) nine subregions of floristics division, and (C) different sides of the Tanaka-Kaiyong Line.
Family Species (% of China) Genus Species (% of China)
Orchidaceae 995 (71%) Rhododendron 349 (54%)
Poaceae 936 (57%) Pedicularis 196 (59%)
Asteraceae 914 (48%) Carex 158 (28%)
Fabaceae 776 (57%) Rubus 146 (52%)
Rosaceae 637 (57%) Primula 144 (43%)
Lamiaceae 530 (59%) Saxifraga 143 (63%)
Ericaceae 514 (55%) Impatiens 139 (59%)
Rubiaceae 441 (65%) Elatostema 125 (73%)
Ranunculaceae 413 (40%) Gentiana 117 (44%)
Primulaceae 331 (49%) Begonia 115 (63%)
Cyperaceae 303 (36%) Ilex 110 (49%)
Apiaceae 278 (55%) Salix 109 (31%)
Urticaceae 275 (72%) Berberis 101 (47%)
Apocynaceae 256 (70%)
Orobanchaceae 239 (49%)
Gesneriaceae 236 (61%)
Lauraceae 235 (52%)
Gentianaceae 221 (50%)
Acanthaceae 193 (67%)
Malvaceae 191 (64%)
Saxifragaceae 173 (59%)
Celastraceae 170 (74%)
Zingiberaceae 164 (85%)
Salicaceae 164 (33%)
Caryophyllaceae 156 (51%)
Araceae 149 (89%)
Euphorbiaceae 148 (78%)
Brassicaceae 148 (51%)
Papaveraceae 146 (34%)
Balsaminaceae 139 (59%)
Araliaceae 138 (77%)
Asparagaceae 137 (57%)
Polygonaceae 135 (73%)
Berberidaceae 131 (44%)
Moraceae 126 (81%)
Cucurbitaceae 120 (77%)
Begoniaceae 115 (63%)
Vitaceae 113 (63%)
Rutaceae 111 (82%)
Aquifoliaceae 110 (49%)
Sapindaceae 106 (60%)
Rhamnaceae 105 (63%)
3.1.2. Distribution of species hotspots in Yunnan

Species richness hotspots are located in counties in SE and NW Yunnan; in contrast, counties in E and C Yunnan have relatively low levels of species richness (Fig. 2A). Gongshan County has the largest number of total species (3, 985). Five additional counties (Shangrila, Jinghong, Pingbian, Jingdong and Deqin) have more than 3, 000 species. Several counties (Weixi, Dali, Xichou, Jinping, Menghai, Malipo, Fugong, Luquan, Hekou and Longling) have 2, 000e3, 000 species (Fig. 2A).

Fig. 2 County-level distribution of plant diversity in Yunnan. (A) Total species distribution patterns. (B) Endemic species distribution patterns. (C) Specimen distribution patterns.(D) New species distribution patterns (from 2013 to 2019). (E) Threatened species distribution patterns. (F) Distribution patterns of Plant Species with Extremely Small Populations(PSESP).

Recent studies suggest that the most phylogenetically important regions are located in E and C Yunnan (Li et al., 2015). Specifically, although species and genera richness and phylogenetic diversity (a diversity) are correlated and indicate that NW and SE Yunnan are hotspots (Li and Yue, 2019), phylogenetic analyses show that eastern regions are similar to western and southern regions, which have higher phylogenetic turnover than expected. Furthermore, phylogenetic b diversity indicates that floristic assemblages in C and NW, E and W Yunnan have closer relationships than traditional taxonomic approaches have shown (Li et al., 2015).

3.1.3. Composition of plant diversity in different climatic zones

From south to north, Yunnan contains three climatic zones: the tropical zone in the southwest, south, and southeastern border; the subtropical zone in the west, middle and east; and the temperate zone in the high-elevation area in the northwest (Yang et al., 2008). The subtropical climatic zone, which has the largest area, harbors the largest numbers of plants: 11, 452 species belonging to 2, 012 genera in 250 families (Fig. 3A). The tropical zone has 7, 199 species belonging 1, 778 genera in 240 families. The alpine-temperate area has 4, 655 species belonging to 1, 024 genera in 241 families.

Fig. 3 Diversity composition of (A) three climate zones, (B) nine subregions of floristics division, and (C) different sides of the Tanaka-Kaiyong Line.
3.1.4. Tanaka-Kaiyong line and floristic divisions

Yunnan is the intersection zone of the Sino-Japan flora and SinoHimalaya flora. The significant floristic subkingdoms line, the "Tanaka-Kaiyong Line" (TK Line), is not only important for the dividing the Sino-Japan flora to the east from the Sino-Himalaya flora to the west, but also because it separates critical species and provides an opportunity to study vicariance (Fan et al., 2013; Li and Li, 1997; Zhu, 2019). Our findings indicate that species diversity is higher to the west of the TK line than to the east, with the west side having 255 families, 2, 227 genera, 13, 657 species, and 392, 441 specimens and the east side having 251 families, 1, 872 genera, 9, 657 species, and 167, 358 specimens (Fig. 3C). Previous research has shown that more endemic genera are distributed to the east of the TK line than to the west, suggesting that the TK line may be a geographical boundary of endemic Chinese seed plant genera in Yunnan (Feng and Zhu, 2010).

Wu et al. (2011) proposed that Yunnan contains the Eastern Asiatic Kingdom and Paleotropic Kingdom and can be categorized into nine floristic subregions (Wu et al., 2011). Our analysis of the composition of plant diversity of these subregions (Fig. 3B) found that the Central Yunnan Plateau subregion has the largest area and contains the largest number of total species (8, 090 species belonging to 1, 690 genera in 248 families). The total number of species for the remaining subregion varied from 1, 454 to 7, 255.

3.1.5. Endemism in the flora of Yunnan

According to Yang et al. (2008), 180 plant genera endemic to China occur in Yunnan. These endemic genera are mostly concentrated in two endemic centers of biodiversity in NW (47) and SE (48) Yunnan. Of these genera, 20 are endemic to Yunnan and the Hengduan Mountains, including Shangrilaia Al-Shehbaz, J.P. Yue & H. Sun, Gaoligongshania D.Z. Li, Hsueh et N.H. Xia, and Tsaiodendron Y.H. Tan, H. Zhu & H. Sun (Al-Shehbaz et al., 2004; Liu and Peng, 2016; Wu and Peter, 1994; Yang et al., 2008; Zhou et al., 2017) (Table 2).

Table 2 Endemic genera in Yunnan and the Hengduan mountains.
N Family Genus Species number Distribution in Yunnan
1 Orchidaceae Smithorchis 1 W
2 Zingiberaceae Pyrgophyllum 1 NW-C
3 Zingiberaceae Siliquamomum 1 SE
4 Musaceae Musella 1 C-W
5 Asteraceae Formania 1 NW
6 Asteraceae Nouelia 1 NW
7 Ranunculaceae Metanemone 1 NW
8 Rubiaceae Trailliaedoxa 1 NW
9 Melastomataceae Cyphotheca 1 S-SW
10 Melastomataceae Sporoxeia 2 S-SW
11 Gesneriaceae Hemiboeopsis 1 SE
12 Apiaceae Chaerophyllopsis 1 NW
13 Lamiaceae Holocheila 1 C-SW, S, SE
14 Lamiaceae Skapanthus 1 NW
15 Apocynaceae Parepigynum 1 SE
16 Poaceae Ferrocalamus 2 S
17 Poaceae Gaoligongshania 1 NW
18 Brassicaceae Shangrilaria 1 NW
19 Euphorbiaceae Tsaiodendron 1 SE
20 Lembophyllaceae Mawenzhangia 1 NW

Earlier studies reported that Yunnan harbors 2, 605 species endemic to China, or 18.4% of all Chinese endemics, and that these endemic species are distributed in Yunnan and in adjacent regions with similar environments (Wu and Peter, 1994). More recent evidence suggests that Yunnan contains 4, 008 endemic species (Chen et al., 2013).Furthermore, 1703 species, which can only be found in Yunnan within China, are also distributed in neighboring regions of the Indochina Peninsular.

The distribution patterns of endemic plant species are highly congruent with those of total plant species (Fig. 2B). The counties with the greatest endemic species richness include Yulong (Lijiang) (549 sp.), Shangrila (Zhongdian) (483 sp.), and Gongshan (465 sp.). Thirty-two counties, most of which are located near Qujing, Yuxi, and Chuxiong, have fewer than 30 endemic species. Hotspots of endemism may have arisen for different reasons. For example, NW Yunnan has likely become a neo-endemic center due to ecological and geomorphological reasons. In contrast, S and SE Yunnan are paleo-endemic centers largely because of their geological history (Li, 1995). These regions may be long-term stable refugia because of the climatic stability provided by the mountains of Yunnan (Tang et al., 2018).

3.1.6. Diversity and distribution of vegetation

Ecosystems in Yunnan range from tropical to alpine zones (Yang et al., 2008). Despite a recent revisions to the vegetation classification system in China (Guo et al., 2018, 2020), research on the vegetation of Yunnan at a province-wide scale is still inadequate (Zhu, 2018). Previous research on vegetation in Yunnan identified 12 vegetation classes, 169 forms, and 209 associations (Wu et al., 1987). More recently, the Ecosystem List of Yunnan Province 2018 (http://bio360.kun.ac.cn/index/ecology) identified 13 vegetation types, 37 vegetation subtypes, and 474 forms (Table 3). The additional vegetation types identified is Desert Vegetation, which is found in the periglacial zone of NW Yunnan. This vegetation type is characterized by several special features, including extreme elevation, rapid speciation, and extreme environments (Yang et al., 2019b). Notably, the subtype Aquatic Community has the largest number of associations (61), due to the variable wetland ecosystem in Yunnan.

Table 3 Vegetation type, vegetation subtype and number of associations in Yunnan.
Vegetation Type Vegetation Subtype Number of Associations
Tropical Rainforest Seasonal Rainforest 19
Tropical Rainforest Montane Rainforest 12
Monsoon Forest Deciduous Monsoon Forest 7
Monsoon Forest Semi-evergreen Monsoon Forest 3
Monsoon Forest Tropical Seasonal Evergreen Moist Forest 4
Evergreen Broadleaf Forest Monsoon Evergreen Broadleaf Forest 26
Evergreen Broadleaf Forest Wet-dry Evergreen Broadleaf Forest 6
Evergreen Broadleaf Forest Moist Evergreen Broadleaf Forest 8
Evergreen Broadleaf Forest Middle-Mountain moist Evergreen Broadleaf Forest 20
Evergreen Broadleaf Forest Mountain bryophyte Evergreen Broadleaf Forest 7
Evergreen Broadleaf Forest Mountain top bryophyte Dwarf Forest 2
Sclerophyllous Evergreen Broadleaf Forest Cold-temperate Montane Evergreen Oak Forest 4
Sclerophyllous Evergreen Broadleaf Forest Dry and Hot Valley Sclerophyllous Evergreen Broadleaf Forest 5
Deciduous Broadleaf Forest Subtropical Deciduous Broadleaf Forest 20
Deciduous Broadleaf Forest Temperate Deciduous Broadleaf Forest 8
Subtropical Needleleaf Forest Subtropical-tropical Needleleaf Forest 3
Subtropical Needleleaf Forest Subtropical-temperate Needleleaf Forest 12
Temperate Needleleaf Forest Temperate-cool Needleleaf Forest 9
Temperate Needleleaf Forest Cold-temperate Needleleaf Forest 14
Bamboo Forest Tropical Bamboo Forest 16
Bamboo Forest Temperate Bamboo Forest 4
Bamboo Forest Cold-temperate Bamboo Forest 3
Savanna-like Shrubby Grassland Dry and Hot Savanna-like Shrubby Grassland 30
Savanna-like Shrubby Grassland Tropical Savanna-like Shrubby Grassland 10
Savanna-like Shrubby Grassland Subtropical-tropical Savanna-like Shrubby Grassland 5
Savanna-like Shrubby Grassland Subtropical-temperate Savanna-like Shrubby Grassland 14
Scrub Dry and Hot Valley Scrub 18
Scrub Tropical River Beach Scrub 1
Scrub Subtropical Limestone Scrub 12
Scrub Temperate-cool Scrub 3
Scrub Cold-temperate Scrub 56
Meadow Cold-temperate Meadow 11
Meadow Alpine Meadow 2
Meadow Forb Meadow 12
Desert Alpine Desert 17
Swamp Aquatic Community 61
Swamp Swampy Meadow 10
3.1.7. Hotspots, new species, and opportunities

Yunnan has long attracted attention from botanists not only in China, but from around the world (Bao et al., 1995; Ma, 2020). This attention increased after the identification of biodiversity hotspots in Yunnan; however, collection activities have been uneven. Our analysis of 526, 501 specimen records of the Herbarium of Kunming Institute of Botany, Chinese Academy of Science (KUN) and NSII indicate that current research efforts are insufficient (Fig. 2C). Specifically, the most-collected county is Gongshan with 38, 203 specimens; second is Shangrila with 35, 288 specimens; and more than 20, 000 specimens have been collected in Deqin, Weixi, Jinghong, Jingdong, and Pingbian. This collection pattern is consistent with species distribution patterns, namely that S and SE Yunnan are heavily-collected regions; however, C, E and NE Yunnan are poorly collected.

From 2013 to 2019 , 163 new higher plant species (an average of 23 species per year) were reported from 53 counties in Yunnan (Fig. 2 D). These newly reported species include two new genera: Mawenzhangia Enroth, Shevock & Ignatov in Shangrila and Tsaiodendron in Yuanjiang (Enroth et al., 2018; Zhou et al., 2017). The distribution of these newly reported species is consistent with total species and specimen distribution patterns. Most new species are distributed in NW, W, S and SE Yunnan in species hotspots in the following counties: Malipo (17 sp.), Gongshan (17 sp.), Mengla (14 sp.), and Yingjiang (11 sp.). However, these new species are not evenly distributed in all families and genera. Most newly reported species are concentrated in Gesneriaceae (22 sp.), Orchidaceae (12 sp.), Dryopteridaceae (12 sp.), Urticaceae (11 sp.) and Liliaceae (10 sp.). Furthermore, only two genera contain more than 10 new species: Polystichum (11 sp.) and Elatostema (10 sp.). One potential reason for this pattern may be that hotspots still contain undiscovered species, and that new species will be discovered upon further investigation. Another reason is that regions that have been relatively fully-investigated have yielded more specimens and information to be studied.

The distribution patterns of collected specimens may reflect the inadequacy of current research (Chen et al., 2013). For example, Vegetation of China (http://nsii.org.cn/chinavegetaion), reports relatively small numbers of recorded species and collected specimens (several hundred) in C, E and NE Yunnan. Cities in these regions (e.g., Qujing, Yuxi, and Chuxiong) are known to have high levels of human activity and cultivated vegetation. Also, other counties, such as Jiangcheng and Ning'er in southern Yunnan and Wenshan on southeastern Yunnan, which are surrounded by several strongly-collected and species-rich counties, show inconsistent specimen and total species numbers. A fuller investigation of counties previously counted by CVH (http://www.cvh.ac.cn/) increased the total number of species reported by 100%e 1000% (Chen et al., 2013; Wu et al., 2016). Species diversity in these areas may be underestimated because researchers pay less attention to counties where human activity is common, traffic conditions are poor, and wild regions are inaccessible due to frequent natural disasters (such as debris flow and landslide) (Chen et al., 2013).

3.1.8. Research and available online databases on plant diversity

As the basic information of species diversity in Yunnan Province, widely used and highly reliable checklists, flora, or monographs are helpful references in management of government departments and social organizations (Christenhusz and Byng, 2016). However, most research focuses on the relationship between biodiversity loss and protection, large scale patterns and formation mechanisms, as well as the mechanisms of community maintenance. Comprehensive studies of systematics are scarce. Major taxonomic advances at Kunming Institute of Botany (KIB) have been summarized for 32 families, including Boletaceae, Poaceae, Begoniaceae, and Theaceae (Feng and Yang, 2018; Tian et al., 2018; Yu et al., 2018). Although there are some available checklists and investigation reports (Table 4), most are related to nature reserves in Yunnan, which cover only a limited area (Yang et al., 2008).

Table 4 Published books, checklists, and reports on plants of Yunnan Province.
Title Year
Flora ofYunnan 1977-2006
Forest of Yunnan 1986
Vegetation of Yunnan 1987
Vascular Plants of the Mts. Hengduan 1994
List of Plants in Xishuangbanna 1996
The Seed Plants from Mt. Wuliang in the South-Central Yunnan, China 1998
Seed Plants of Honghe Region in SE Yunnan, China 2003
Yunnan Mt. Luchun Huanglianshan Natural Reserve 2003
Ferns of Mt. Ailao 2007
List of Seed Plants in the Mt. Ailao of Yunnan Province, China 2009
Vascular Plants of the Dali CangShan ErHai National Natural Reserve 2010
Research on the Seed Plants and Forest Vegetation in Mt. Yongdedaxueshan 2010
A Checklist of the Flowering Plants in Southeast Yunnan 2010
Checklist of Seed Plants of Mt. Yaoshan NE Yunnan 2010
Plants in Dabaoshan Black-Necked Crane Nature Reserve, China 2010
List of wetland plants in Yunnan 2010
Native Seed Plants in Xishuangbanna of Yunnan 2012
Seed Plans of the Alpine Subnival Belt from the Mts. Hengduan, SW China 2013
Yunnan Mt. Jiaozishan National Natural Reserve 2015
Seed Plants of Mt. Xilongshan, the First Peak in South Yunnan, China 2016
The Checklist of Biological Species from Yunnan ( 2016 ) 2016
Checklist of Seed Plants in the Karst Regions in China 2017
Species Red List of Yunnan Province 2017
Integrated Scientific Reports of Mt. Daweishan National Nature Reserve of Yunnan, China 2018
Ecosystem List of Yunnan Province 2018 2018
Catalogue of Seeds 2018 Germplasm Bank of Wild Species 2018
Invasive Species List of Yunnan Province 2019
Study and Conservation of Plant Species with Extremely Small Populations (PSESP) in Yunnan Province, China 2019

Online biodiversity resources and data sharing have advanced considerably in China and Yunnan (Wang et al., 2017) (Table 5). The most recent comprehensive database specifically focused on biodiversity in Yunnan is the Holographic Database of Plants (http://bio360.kun.ac.cn/index), which includes a database of The Checklist of Biological Species from Yunnan (2016 ). In addition, various public science projects, such as the Chinese Natural Herbarium (http://www.cfh.ac.cn/) and Biotracks (http://www.biotracks.cn/), have provided massive data for biodiversity research. Citizen scientists provide a wide range of observational data, but much of this data may also be inaccurate (Lv et al., 2015; Zhang et al., 2013).

Table 5 Available databases about biodiversity in Yunnan.
Database Name Website Description
Holographic Database of Plants http://bio360.kun.ac.cn/ Comprehensive database of plant diversity in Yunnan
Kingdonia http://kun.kingdonia.org/ Specimen database of KUN, 810, 718 plant specimens of Yunnan, developed by KIB
Biotracks http://www.biotracks.cn Biodiversity on the map, exhibiting combined information of plant digit specimen, collection information, photos, expedition tracks, developed by KIB
Germplasm Bank of Wild Species http://www.genobank.org The Germplasm Bank of Wild Species (Information on germplasm resources of ca. 10, 096 collected), developed by KIB
iFlora http://www.iflora.cn/if/default.aspx Information on plant taxonomy, distribution, identification, and resources, developed by KIB
Plant Introduction and Conservation Database http://sdb.xtbg.ac.cn/page/index.vpage Comprised by plant phenology and plant growth records, and other information, created by XTBG
NSII (National Specimen Information Infrastructure) http://www.nsii.org.cn National database that contains information on biodiversity of Yunnan
Species 2000 China Node http://www.sp2000.org.cn/ National database that contains information on biodiversity of Yunnan
Subject Database of China Plant http://www.plant.csdb.cn/ National database that contains information on biodiversity of Yunnan
Scientific Database of China Plant http://db.kib.ac.cn/ National database that contains information on biodiversity of Yunnan
Species
Plant Plus of China http://www.plantplus.cn/ National database that contains information on biodiversity of Yunnan
Due to the continuous emergence of new biodiversity data, these databases do not cover all the progress in the area of biodiversity information.
3.2. Threatened and conservation status in Yunnan 3.2.1. Status of the Red List and threatened species

In 2017 , the first Red List of a province in China, the Species Red List of Yunnan Province (2017 ) (http://bio360.kun.ac.cn/index/redlist), was released, providing a more comprehensive picture of the conservation status of species in Yunnan than previous work (Red list of China's biodiversity - Volume of higher plants, http://www.mee.gov.cn/gkml/hbb/bgg/201309/t20130912_260061.htm). Of 3, 767 threatened species (IUCN Threatened Categories include Critically Endangered, Endangered, and Vulnerable) in China, 1, 426 species are distributed in Yunnan (Table 6). The distribution patterns of threatened species in Yunnan is consistent with those of total species and endemic species (Fig. 2E). "Hotspots" of threatened species are located in NW, S and SE Yunnan. Specifically, most threatened species are in Mengla (442), Jinghong (393), Gongshan (360) Lijiang (358), and Pingbian (337).

Table 6 Conservation status of plants in Yunnan and China.
Category Moss and Liverwort Fern Gymnosperm Angiosperm Higher Plants in Yunnan, 2017 Higher Plants in China, 2013
Extinct (EX) 1 0 0 4 5 27
Extinct in the Wild (EW) 0 0 0 2 2 10
Regional Extinct (RE) 0 0 0 2 2 15
Critically Endangered (CR) 38 13 10 224 285 583
Endangered (EN) 18 39 16 627 700 1297
Vulnerable (VU) 34 107 13 915 1069 1887
Near Threatened (NT) 29 131 7 1770 1937 2723
Data Deficient (DD) 140 405 9 988 1542 3612
Least Concern (LC) 1647 594 45 10577 12863 24296

Two important points must be noted. First, the number of threatened species in every category has remained high in China since the red list was published in 2013 . Second, the number of species categorized as Data Deficient (DD) is very high. Furthermore, assessing the current conservation status of two types of species poses challenges: (1) newly described species for which basic biological and ecological information is lacking and (2) species with doubtful taxonomic status (Zang et al., 2016). Researchers have paid more attention to economic and protected species and less attention to the narrowly distributed species. However, categorizing species DD does not mean that the species is not endangered; in contrast, its survival status is not clear at all, and many of these species may even be extinct.

A recent example of the unclear survival status of a species is the re-discovery of Hemilophia serpens (O. E. Schulz) Al-Shehbaz, which was 'refound' in 2019 near the Type location after first being discovered by Handel-Mazzetti in 1915 in Zhongdian (Shangrila) (Fig. 4A). For 104 years, there were no records or specimens of this 'type-only' species. Other 'type-only' species have also been rediscovered (Fig. 4B, C, D), for example, Paraisometrum mileense W. T. Wang, which was first collected in 1906 in Mile, and Brachymeniopsis gymnostoma Broth., which was first collected in 1916 in Lijiang (Chen et al., 2014; Jia, 2017). Both species were regarded as extinct in the wild until their recent re-discovery in Shilin (Yunnan) and Yadong (Tibet) confirmed that the species exist in the wild (Chen et al., 2014; Jia, 2017). These discoveries emphasize that species categorized as DD may be among the most threatened species and require increased attention from researchers in the future.

Fig. 4 Type specimens and recent photographs of re-discovered 'type-only' species. (A) Hemilophia serpens (published in 1915). (B) Ranunculus melanogynus (published in 1960). (C)Carex polymascula (published in 1983). (D) Delphinium oxycentrum (published in 1937).
3.2.2. Conservation status for all plants and Plant Species with Extremely Small Populations (PSESP)

(1) Traditional and modern in situ conservation

China has a long history of nature conservation. Traditional conservation is based on plant and mountain worship, and relies on traditional culture and morality for enforcement. In contrast, modern conservation is based on the scientific method, and has established nature reserves with monitoring and management systems (Liu et al., 2000; Yang et al., 2019a; Zou et al., 2005). Historically, areas important to local minorities, such as Meili Snow Mountain in Yunnan, have been designated as "sacred mountains" (Wang, 2000; Yang et al., 2019a). More than half of China's ethnic minority groups reside in Yunnan, and fifteen of these 25 ethnic minorities reside only in Yunnan (People's Government of Yunnan, http://www.yn.gov.cn). Local traditional culture plays an important role in biodiversity conservation (Liu et al., 2000; Yang et al., 2019a; Zou et al., 2005). However, traditional cultures are generally constricted to limited areas and much traditional knowledge of ecology is increasingly being lost (Zou et al., 2005). Thus, modern conservation systems are urgently needed.

(2) In situ conservation in Yunnan

In situ conservation has practical significance for maintaining the reproduction and evolution of organisms in the ecosystem, and is the most effective measure in biodiversity protection (Ma et al., 2012). The first nature reserve of Yunnan, the Xishuangbanna Nature Reserve, was established in 1958 and covers more than 10% of Xishuangbanna Prefecture, harboring about 3, 500 higher plants (Lopez Pujol et al., 2006). As of 2016 , a total of 160 nature reserves ° have been established, accounting for 7.3% of the province's land area. Furthermore, the number and area of nature reserves ranks sixth and ninth in China, respectively (Yunnan Forestry and Grassland Bureau, 2016 ). In Yunnan, there are 21 National Nature Reserves, 38 Provincial Nature Reserves, 56 Municipal Nature Reserves, and 45 County Nature Reserves. Out of 129 counties in Yunnan, 109 have at least one nature reserve (Fig. 5). The higher-level nature reserves (e.g., National and Provincial Nature Reserves) cover almost all the biodiversity hotspots in Yunnan, whereas the lowerlevel nature reserves (e.g., Municipal and County level Nature Reserves) are more concentrated in the C, E and NE Yunnan. For example, the county with the largest number of nature reserves in Yunnan is Huize County (7), which is located in NE Yunnan (Fig. 5E). However, the total area of nature reserves in Huize County is below average (Fig. 5J). Because human activity increasingly fragments natural habitats, it is difficult to conserve large areas; thus, establishing small conservation areas may be an important strategy to protect local biodiversity. Moreover, even though 84.5% of counties in Yunnan have nature reserves, there are still many conservation gaps or unprotected areas that harbor threatened species (Wang et al., 2018; Yang et al., 2013; Ye et al., 2020).

Fig. 5 Current status of nature reserves in Yunnan. (AeE) Number and county location of nature reserves. (FeG) Area (hm2) of nature reserves in county level distribution. (A and F)All nature reserves. (B and G) National nature reserves. (C and H) Provincial nature reserves. (D and I) Municipal nature reserves. (E and J) County nature reserves.

(3) Ex situ conservation in Yunnan

Botanical gardens play the most important role of scientific research and conservation in terms of ex situ protection (Chen and Sun, 2018). There are 10 botanical gardens and arboretums in Yunnan, eight of which are members of the Union of Chinese Botanical Gardens, which consists of 116 botanical gardens in China, including Xishuangbanna Tropical Botanical Garden (XTBG) and Kunming Botanical Garden (KBG). XTBG covers an area of about 1, 125 hm2, contains more than 12, 000 kinds of living plants, has 38 special collection botanical areas, and preserves a piece of original tropical rain forest with an area of about 250 hm2. It is the largest botanical garden in China with the most species collected and the most special theme areas. The KBG is a comprehensive botanical garden with an open area of 44 hm2, 18 special collection areas, and a collection of more than 8, 700 species. Other botanical gardens, such as Kunming Arboretum of Yunnan Academy of Forestry Sciences, also play important roles in preserving the threatened and endangered plants (Botanical Garden Committee of Chinese Academy of Sciences, 2019 ).

In addition to botanical gardens, the Germplasm Bank of Wild Species in Kunming is also an important organization for ex situ conservation. To date, the germplasm bank has collected wild seeds of 10, 018 species, 80, 105 copies, belonging to 228 families and 2, 005 genera (Li, 2018).

(4) Near situ conservation and PSESPs in Yunnan

Near situ conservation aims to protect small populations of wild plants, such as Plant Species with Extremely Small Populations (PSESPs) (Sun and Han, 2015). Ten near situ conservation gardens have been established in Yunnan and more PSESP work is ongoing, including the protection of 60 PSESPs in situ and 80 PSESPs ex situ (Sun and Han, 2015; Sun et al., 2019; Wang et al., 2020b; Yang et al., 2020).

A total of 120 PSESPs (Appendix 1) in southern China (Zhang et al., 2018) and 62 PSESPs (Appendix 2) in Yunnan require urgent protection. We found that SE Yunnan is a PSESP hotspot (Fig. 2F). Specifically, PSESP hotspots are located in Hekou (15 sp.), Pingbian (13 sp.), Jinping (13 sp.), Xichou (11 sp.), Malipo (11 sp.) and Maguan (10 sp.) counties. In addition, we identified six counties that have at least one PSESP but no nature reserves: Luxi, Fumin, Shilin, Songming, Yanshan and Ancient Town District (Lijiang) (Fig. 6).

Fig. 6 Conservation gaps in Yunnan.
4. Conclusion: current problems and recommendations 4.1. Survey data lack detailed GPS information

Although millions of specimens have been collected and are available, very few records of these specimens include detailed GPS information. Based on our roughly random sampling, 8.3% and 73.8% specimens collected from 1990 to 1995 and 2015 to 2019 have accurate GPS information, respectively. Because climatic niche inference is sensitive to distribution data sampling, the countylevel distribution data may introduce elevational bias into climate niche estimates (Pender et al., 2019).

4.2. The accuracy of specimen identification needs to be improved

Previous research showed that an estimated 50% of the world's collected tropical specimens may be incorrectly identified (Goodwin et al., 2015). We have roughly calculated (together with data from experts) that 35% of specimens in herbaria are inaccurately identified. Accurate identification is the basis of all other work and inaccurate identification greatly impacts research. Today, systematists pay more attention to gathering and analyzing molecular data than to doing traditional taxonomic work (i.e., field work and identification). Consequently, the new generation of systematists relies on the accurate identification of herbarium specimens. If these researchers fail to accurately identify material collected from the wild, future research will be of limited value (Yu et al., 2018).

4.3. Species information in databases needs to be improved

The digitization of biodiversity data may provide many opportunities for biodiversity researchers (Wang et al., 2017, 2020a), but it also brings challenges: (1) these data resources are distributed over different platforms and articles, which are difficult to retrieve, update and collect; (2) because of the complexity of biodiversity itself, it is difficult to have a comprehensive understanding of a database over a short time, and some researchers may misuse the database, for example, by analyzing data directly without standardization or without checking null values; (3) there is a lot of data overlap, regional bias and incompleteness, including geographical coordinate errors and synonym problems, which may affect our understanding of biodiversity patterns (Meyer et al., 2016; Qian et al., 2018; Wang et al., 2017).

4.4. Future perspectives

Protecting the plant diversity of Yunnan will require much future work. We recommend that specimens in all areas of Yunnan be cleaned-up, poorly-collected areas (e.g., C, NE and E Yunnan) be investigated, and the locations of Data Deficient and 'type-only' species be re-investigated. Furthermore, specimen documentation should include GPS information and photos, and efforts should be made to build a framework for an integrated big data database that strengthens research on all taxa (including unpublished flora volumes of cryptogams). Protecting plant diversity in Yunnan will also require compiling district and/or county-level flora and more creative monographs (Liu and Peng, 2016; Lu et al., 2012; Yu et al., 2018; Zhang et al., 2012). We should also establish a more functional and integrated protection system, strengthen the protection of genetic diversity and pay more attention to popularizing science and environmental education (Chen and Sun, 2018; Lv et al., 2015; Sun and Han, 2015).

Author contributions

H.S., T.D. and J.H.C. planned and designed the research; J.H.C. collected and provided the data; L.S.Q. analyzed data; L.S.Q. wrote the manuscript.

Declaration of competing interest

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

Acknowledgement

We thank Dr. Jian-Wen Zhang, Dr. Yang Niu, Dr. Dong Luo, JunChu Peng, Lu Sun, and Ya-Zhou Zhang for their thoughtful comments and patient help with this manuscript. This study was supported by the National Key R & D Program of China (2017YFC0505200), the Second Tibetan Plateau Scientific Expedition and Research (STEP) program (2019QZKK0502), the Strategic Priority Research Program of Chinese Academy of Sciences (XDA20050203), and the Key Projects of the Joint Fund of the National Natural Science Foundation of China (U1802232).

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi.org/10.1016/j.pld.2020.07.006.

References
Al-Shehbaz I., Yue J.P., Sun H., 2004. Shangrilaia (Brassicaceae), a new genus from China.. Novon, 14(3): 271-274.
Bao S.Y., Mao P.Y., Yuan S.X., 1995. A Brief History of Plant Collection in Yunnan. Beijing: China Science and Technology Press.
Chen G., Sun W.B., 2018. The role of botanical gardens in scientific research, conservation, and citizen science.. Plant Divers, 40(4): 181-188. DOI:10.1016/j.pld.2018.07.006
Chen L., Dong H.J., Peng H., 2013. Diversity and distribution of higher plants in Yunnan, China. Biodivers. Sci, 21(3): 359-363.
Chen W.H., Shui Y.M., Yang J.B., et al, 2014. Taxonomic status, phylogenetic affinities and genetic diversity of a presumed extinct genus, Paraisometrum W.T.Wang (Gesneriaceae) from the Karst regions of southwest China.. PloS One, 9(9): e107967. DOI:10.1371/journal.pone.0107967
Cheng W.M., Zhou C.H., Li B.Y., et al, 2019. Geomorphological regionalization theory system and division methodology of China. Acta Geol. Sin, 74(5): 839-856.
Christenhusz M.J.M., Byng J.W., 2016. The number of known plants species in the world and its annual increase.. Phytotaxa, 261(3): 201-217. DOI:10.11646/phytotaxa.261.3.1
Enroth J., Shevock J.R., Ignatov M.S., 2018. Mawenzhangia thamnobryoides (Bryophyta, Lembophyllaceae), a new moss genus and species from the Shangri-la region of Yunnan Province, China.. Phytotaxa, 346(3): 237-247. DOI:10.11646/phytotaxa.346.3.3
Fan D.M., Yue J.P., Nie Z.L., et al, 2013. Phylogeography of Sophora davidii (Leguminosae) across the nTanaka-Kaiyong lineo, an important phytogeographic boundary in southwest China. Mol. Ecol, 22(16): 4270-4288. DOI:10.1111/mec.12388
Feng B., Yang Z., 2018. Studies on diversity of higher fungi in Yunnan, southwestern China: a review.. Plant Divers, 40(4): 165-171. DOI:10.1016/j.pld.2018.07.001
Feng J.M., Zhu Y.Y., 2010. On the genera of seed plants endemic to China in Yunnan Ecol. Environ. Sci, 19(3): 621-625.
Goodwin Z.A., Harris D.J., Filer D., et al, 2015. Widespread mistaken identity in tropical plant collections. Curr. Biol, 25(22): R1066eR1067.
Guo K., Fang J.Y., Wang G.H., et al, 2020. A revised scheme of vegetation classification system of China. Chin. J. Plant. Ecol, 44(2).
Guo K., Liu C.C., Xie Z.Q., et al, 2018. China vegetation classification: concept, approach and applications.. Phytocoenologia, 48(2): 113-120. DOI:10.1127/phyto/2017/0166
Jia Y., 2017. Wonderful story of rare bryophytes.. Chin. Nat, (3): 31-33.
Li B.Y., Pan B.T., Cheng W.M., et al, 2013. Research on geomorphological regionalization of China. Acta Geol. Sin, 68(3): 291-306.
Li D.Z., 2018. Catalogue of Seeds 2018 Germplasm Bank of Wild Species. Science Press: Beijing.
Li R., Kraft N.J.B., Yang J., et al, 2015. A phylogenetically informed delineation of floristic regions within a biodiversity hotspot in Yunnan, China. Sci. Rep, 5: 9396. DOI:10.1038/srep09396
Li R., Yue J., et al, 2019. A phylogenetic perspective on the evolutionary processes of floristic assemblages within a biodiversity hotspot in eastern Asia. J. Systemat.Evol.
Li X.W., 1995. A floristic study on the plants from the region of Yunnan Plateau.. Acta Bot. Yunnanica, 17(1): 1-14.
Li X.W., Li J., 1997. The Tanaka-Kaiyong Line-an important floristic line for the study of the flora of East Asia. Ann. Mo. Bot. Gard, 84(4): 888-892. DOI:10.2307/2992033
Liu A.Z., Pei S.J., Chen S.Y., 2000. An investigation and study on the plant worship by Yi people in Chuxiong, Yunnan. Biodivers. Sci, 8(1): 130-136.
Liu Z.W., Peng H., 2016. Notes on the key role of stenochoric endemic plants in the floristic regionalization of Yunnan.. Plant Divers, 38(6): 289-294. DOI:10.1016/j.pld.2016.11.011
L#243;pez Pujol J. Zhang F.M., Ge S., 2006. Plant biodiversity in China: richly varied, endangered, and in need of conservation. Biodivers. Conserv, 15(12): 3983-4026. DOI:10.1007/s10531-005-3015-2
Lu L., Wang H., Li D.Z., 2012. Some considerations on data integration for the next generation Flora (iFlora) and flora revision-a case study of Gaultheria (Ericaceae). Plant Divers. Resour, 34(6): 562-584. DOI:10.3724/SP.J.1143.2012.12145
Lv Z., Gu L., Wen C., et al, 2015. China Nature Watch 2014: an independent report on China's biodiversity conservation status. Biodivers. Sci, 23(5): 570-574. DOI:10.17520/biods.2015116
Ma J.S., 2020. A Chronicle of Plant Taxonomy in China. Zhengzhou: Henan Science and Technology Press.
Ma J.Z., Rong K., Cheng K., 2012. Research and practice on biodiversity in situ conservation in China: progress and prospect. Biodivers. Sci, 20(5): 551-558.
Meyer C., Weigelt P., Kreft H., 2016. Multidimensional biases, gaps and uncertainties in global plant occurrence information. Ecol. Lett, 19(8): 992-1006. DOI:10.1111/ele.12624
Pender J.E., Hipp A.L., Hahn M., et al, 2019. How sensitive are climatic niche inferences to distribution data sampling? A comparison of Biota of North America Program (BONAP) and Global Biodiversity Information Facility (GBIF) datasets. Ecol. Inf, 54: 100991. DOI:10.1016/j.ecoinf.2019.100991
Qian H., Deng T., Beck J., et al, 2018. Incomplete species lists derived from global and regional specimen-record databases affect macroecological analyses: a case study on the vascular plants of China. J. Biogeogr, 45(12): 2718-2729. DOI:10.1111/jbi.13462
Sun H., Gao Z.W., 2016. The Checklist of Biological Species from Yunnan (2016). Kunming: Yunnan Science and Technology Press.
Sun W.B., Han C.Y., 2015. Researches and conservation for plant species with extremely small populations (PSESP). Biodivers. Sci, 23(3): 426-429.
Sun W.B., Yang J., Dao Z.L., 2019. Study and Conservation of Plant Species with Extremely Small Populations (PSESP) in Yunnan Province, China. Beijing: Science Press.
Tang C.Q., Matsui T., Ohashi H., et al, 2018. Identifying long-term stable refugia for relict plant species in East Asia. Nat. Commun, 9(1): 4488.
Tian D.K., Xiao Y., Tong Y., et al, 2018. Diversity and conservation of Chinese wild begonias.. Plant Divers, 40(3): 75-90. DOI:10.1016/j.pld.2018.06.002
Wang K., Zhao M.J., Su J.H., et al, 2020a. The use of Checklist of Fungi in China database in the red list assessment of macrofungi in China. Biodivers. Sci, 28(1): 74-99.
Wang S.M., Dou H.S., 1998. Lakes of China. Beijing: Science Press.
Wang W., Feng C.T., Liu F.Z., et al, 2020b. Biodiversity conservation in China: a review of recent studies and practices. Environ. Sci. Ecotechnol, 1016. DOI:10.1016/j.ese.2020.100025
Wang X., Zhang F.l., Zhang J., 2017. Biodiversity information resources. I. Species distribution, catalogue, phylogeny, and life history traits. Biodivers. Sci, 25(11): 1223-1238. DOI:10.17520/biods.2017184
Wang X.L., 2000. The contribution of ancient Chinese to knowledge and protection of biodiversity. Biodivers. Sci, 8(4): 429-434.
Wang Y., Yu C.Y., Yang D., et al, 2018. Study on conservation gap of natural reserves in Yunnan Province. For. Inventory Plann, 43(4): 55-58+62.
Wu J.Y., Peng H., Jiang X.L., et al, 2016. An inventory of county-level biodiversity in Northwest Yunnan. Biodivers. Sci, 24(12): 1414-1420. DOI:10.17520/biods.2016154
Wu Z.Y., Peter H.R., 1994. Flora of China. Beijing: Science Press.
Wu Z.Y., Sun H., Zhou Z.K., et al, 2011. Floristics of Seed Plants from China. Beijing: Science Press.
Wu Z.Y., Zhu Y.C., Jiang H.Q., 1987. Vegetation of Yunnan. Beijing: Science Press.
Yang F.L., Hu J.M., Wu R.D., 2013. Identifying plant priority conservation areas based on the NPWP distribution in Yunnan, China. Acta Geol. Sin, 68(11): 1538-1548.
Yang J., Cai L., Liu D.T., et al, 2020. China's conservation program on plant species with extremely small populations (PSESP): progress and perspectives. Biol.Conserv, 244.
Yang L., Li H., 2010. Wetlands of Yunnan. Beijing: China Forestry Publishing House.
Yang L.X., Pei S.J., Zhang Y., 2019a. Action research on Tibetan sacred nature sites(SNS) conservation in Tibetan community in NW Yunnan. Biodivers. Sci, 27(7): 749-757. DOI:10.17520/biods.2019081
Yang Y., Chen J.G., Song B., et al, 2019b. Advances in the studies of plant diversity and ecological adaptation in the subnival ecosystem of the Qinghai-Tibet Plateau. Chin. Sci. Bull, 64(27): 2856-2864. DOI:10.1360/TB-2019-0054
Yang Y.M., Wang J., Wang J.H., et al, 2008. Studies on the Biodiversity and its Conservation in Yunnan, China. Beijing: Science Press.
Ye P.C., Zhang G.F., Wu J.Y., 2020. Hotspots and conservation gaps: a case study of key higher plant species from Northwest Yunnan, China. Glob. Ecol. Conserv.
Yu X.Q., Xiang C.L., Peng H., 2018. Taxonomy in the Kunming Institute of Botany(KIB): progress during the past decade (2008-2018) and perspectives on future development. Plant Divers, 40(4): 147-157. DOI:10.1016/j.pld.2018.07.002
Zang C.X., Cai L., Li J.Q., et al, 2016. Preparation of the China biodiversity red list and its significance for biodiversity conservation within China. Biodivers. Sci, 24(5): 610-614. DOI:10.17520/biods.2015272
Zhang J., Chen S.B., Chen B., et al, 2013. Citizen science: integrating scientific research, ecological conservation and public participation. Biodivers. Sci, 21(6): 738-749.
Zhang M.G., Zhou Z.K., Chen W.Y., et al, 2012. Using species distribution modeling to improve conservation and land use planning of Yunnan, China. Biol. Conserv, 153(2012): 257-264.
Zhang Z.J., Gu Y.P., He J.S., et al, 2018. Conservation status of wild plant species with extremely small populations in China. Biodivers. Sci, 26(6): 572-577. DOI:10.17520/biods.2017271
Zhou Z., Gu B.-J., Sun H., et al, 2017. Molecular phylogenetic analyses of Euphorbiaceae tribe Epiprineae with the description of a new genus, Tsaiodendron gen.nov., from south-western China. Bot. J. Linn. Soc, 184: 167-184.
Zhu H., 2018. A sketch of the classification of the tropical forest vegetation in Yunnan.. Guihaia, 38(8): 984-1004.
Zhu H., 2019. The Tanaka Line and its application as a biogeographic floristic line. Plant Sci. J, 5(36): 761-766.
Zou L., Xie Z.Q., Ou X.K., 2005. Significance of Tibetan sacred hills in nature conservation of Shangri-La Gorge, Yunnan. Biodivers. Sci, 13(1): 51-57.
Botanical Garden Committee of Chinese Academy of Sciences, 2019. Annual Report of Botanical Gardens, Chinese academy of science. https://www.cubg.cn/Download/Report/2020/03/06/2865.html. (Accessed 15 April 2020).
Ministry of Ecology and Environment of the People's Republic of China, 2018a. The Bulletin of China's Ecological Environment. http://www.mee.gov.cn/hjzl/tj/201905/t20190529_704850.shtml. (Accessed 15 April 2020).
Yunnan Forestry and Grassland Bureau, 2016. Annual Report of Yunnan Nature Reserve. http://lcj.yn.gov.cn/8415/8419/8660/8669/114841.html. (Accessed 15 April 2020).
Ministry of Ecology and Environment of the People's Republic of China, 2018b. Regulations of Yunnan Province on Biodiversity Conservation Officially Released. http://www.mee.gov.cn/xxgk/gzdt/201810/t20181017_662666.shtml.(Accessed 4 June 2020).