Orchidaceae are widely distributed in many terrestrial ecosystems except for polar and desert areas and constitute a “flagship group” in biological conservation. As the largest tropical island of China, Hainan has five tropical forest vegetation types, namely deciduous monsoon forest, lowland rainforest, montane rainforest, montane evergreen forest, and montane cloud forest. There are 317 orchid species in the island, including 33 endemic, 158 epiphytic, 148 terrestrial, and 11 saprophytic species. Most orchids, which are mainly located in central and southern parts of the island, are generally distributed in damp tropical forests in mountains at an altitude of 500–1500 m. Highest level of endemism is also centred in these areas. Orchids are especially threatened by habitat fragmentation because they grow in small populations, and fragmentation may block gene flow and result in lower genetic diversity. In addition, due to their ornamental and medicinal value, many orchids are over-collected. Therefore, orchid conservation in Hainan Island is very urgent. The aim of this article is to determine the distribution pattern of orchids and expound research and conservation status in Hainan Island, and to propose conservation strategies for the future.
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兰科植物广泛分布于除北极和沙漠地区之外的陆地生态系统,是保育生物学中的旗舰类群。海南岛为中国最大的热带岛屿,具有落叶季风林、低地雨林、山地雨林、山地常绿林和山地云雾林五种热带森林类型。海南岛分布有317种兰科植物,包括158种附生兰、148种地生兰和11种腐生兰;其中33种为海南岛所特有。大多数兰科植物分布在海南岛中部和南部的山区,其栖息地为潮湿的热带森林,海拔约为500-1500 m;此地区同样为兰科植物的特有性中心。海南岛兰科植物居群较小,生境片段化阻碍居群间的基因流,使其面临着居群多样性减小从而导致居群衰退的威胁。加之兰科植物较高的观赏和药用价值,许多的野生植株被盗采盗挖。因此,海南岛兰科植物的保育工作非常迫切。本文致力于阐述海南岛兰科植物的分布特征,分析其保育状况并提出将来的保育策略。
As one of the largest angiosperm families, Orchidaceae contains about 870 genera and 27,000 species (
In Hainan, orchid species are distributed in various forest types (
In this article, we aim to determine the orchids’ distribution pattern and to identify the diversity and endemic centres in Hainan Island. We will also introduce the state-of-the-art of the research and conservation status of Hainan’s orchids, in order to discern whether or not the location of the current nature reserves is reasonable. Furthermore, according to the data collected, we propose conservation strategies for the future.
There are 102 genera and 317 orchid species distributed in Hainan Island (
Genus | Species number | Genus | Species number | Genus | Species number |
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3 |
|
2 |
|
1 |
|
2 |
|
2 |
|
5 |
|
1 |
|
4 |
|
3 |
|
4 |
|
1 |
|
1 |
|
3 |
|
1 |
|
1 |
|
3 |
|
4 |
|
4 |
|
2 |
|
2 |
|
2 |
|
2 |
|
1 |
|
3 |
|
1 |
|
6 |
|
3 |
|
25 |
|
1 |
|
3 |
|
11 |
|
3 |
|
1 |
|
1 |
|
7 |
|
3 |
|
1 |
|
1 |
|
1 |
|
2 |
|
13 |
|
1 |
|
1 |
|
1 |
|
1 |
|
2 |
|
1 |
|
1 |
|
1 |
|
5 |
|
1 |
|
11 |
|
1 |
|
1 |
|
1 |
|
1 |
|
1 |
|
2 |
|
18 |
|
2 |
|
2 |
|
1 |
|
2 |
|
1 |
|
2 |
|
1 |
|
6 |
|
2 |
|
1 |
|
1 |
|
1 |
|
1 |
|
1 |
|
1 |
|
1 |
|
17 |
|
2 |
|
5 |
|
1 |
|
1 |
|
1 |
|
18 |
|
2 |
|
6 |
|
2 |
|
2 |
|
2 |
|
1 |
|
4 |
|
3 |
|
1 |
|
1 |
|
3 |
|
1 |
|
10 |
|
1 |
|
1 |
|
3 |
|
1 |
|
1 |
|
1 |
|
9 |
Province | Area (km2) | Genera | Species | Number of species / 100 km2 |
---|---|---|---|---|
Hainan Island | 33,920 | 102 | 318 | 0.94 |
Taiwan Island | 35,873 | 101 | 322 | 0.90 |
Yunnan Province | 420,645 | 135 | 746 | 0.18 |
Guangdong Province | 179,800 | 83 | 263 | 0.15 |
Guangxi Province | 236,700 | 94 | 286 | 0.12 |
Geographic distribution of orchids tends to be not homogeneous. Both the species diversity and endemism centres are located in the central and southern parts of the island, which are mountainous regions. Species in Baoting, Lingshui and Sanya counties account for more than 80% of the total number in Hainan Island (
The concept “species irreplaceability” first came up in Pressey
In Hainan Island, orchids are mainly distributed in tropical forests of mountains at an altitude of 500–1500 m. There are a lot of epiphytic orchids in the tropical forests. Epiphytic orchids mainly grow on the trunks or branches of tall trees. Many populations of wild orchids are small, and easily destroyed by habitat fragmentation. As a result, recruitment of new individuals in populations is diminished. Until now, specific research in population dynamics has been carried out in several orchid species such as
The conservation of biological diversity is ultimately depending on the preservation of genetic diversity (
Many orchids are specialists depending on only one (or a few) mycorrhizal fungi and pollinators. This specificity added to its narrow range and small population sizes make orchids especially vulnerable to climate change, human disturbance, and habitat fragmentation. Furthermore, many orchids have high ornamental (
In situ conservation is aimed to protect wildlife in their natural habitats, which ensures the maintaining of ecological processes and the ongoing processes of evolution. At present, there are ten National Nature Reserves established in Hainan Island, namely Yinggeling, Bawangling, Jianfengling, Tongguling, Wuzhishan, Diaoluoshan, Datian, Dongzhaigang, Sanya Coral Reefs, and Dazhou Island (
Nevertheless, many requirements should be met to establish a nature reserve. Besides, ex situ conservation can be used as a complementary method for orchid conservation. In the context of
At present, the main method of ex situ conservation of Orchidaceae in Hainan Island is the establishment of nurseries through tissue culture, and current research focuses on the study of mycorrhizal biology to improve seedlings’ survival rate in several species, including
Establishment of natural reserves should not be only based on genetic and species diversity but also on ecological diversity. Because it is not possible to comprehensively assess the genetic diversity of over 300 orchid species in a short time, priority should be given to a smaller set of species. The most endangered, rare and regionally unique species should be in the front row for molecular studies on population genetic structure. Populations with higher genetic diversity should be protected with in situ
In Hainan Island up to 397 endemic species have been recorded so far (
Regions with low species diversity of orchids in Hainan Island are not among the best candidates to be covered by nature reserves, as occurs elsewhere. In this case, ex situ conservation is probably the only option to reduce the declining of populations or endangered species. Plants can be taken back to the breeding bases and nurseries to propagate them with tissue culture methods and the use of mycorrhizal interactions. Tissue cultured experiments of artificial hybridization can also be carried out in plantlets for improving diversity. When the conditions are appropriate, these plants can be reintroduced into their natural habitats. Therefore, large-scale propagation and mycorrhizal biology research of orchids should become one the most urgent and important issues regarding their conservation. In addition, the reintroductions should be combined with population genetics research to assess adaptation after reintroduction.
The scientific and feasible approaches to strengthen conservation of orchids in Hainan Island are important. What is more, there should be some regulations to solve the problem that local people collect orchids excessively to pursuit the profit stemming from the high ornamental and medicinal value of these plants. We must also take some non-academic actions to collaborate and co-work with local governments, communities and NGOs to promote the conservation of orchids.
We thank Prof. M.-X. Ren and Dr. Q. Ding for their helpful suggestions. This research was supported by the National Natural Science Foundation of China (31160178) and Special Fund for Agro-scientific Research in the Public Interest (201303117). It is also partially supported by Academic Discipline Construction Project in the Central and Western Regions of China to Hainan University (ZXBJH-XK008).