斯里蘭卡樹蕨（桫欏科, Cyatheaceae）的保育優先性

Conservation Priorities for Tree Ferns (Cyatheaceae) in Sri Lanka

本文探討斯里蘭卡樹蕨的多樣性、植物地理和保護現狀。斯里蘭卡的桫欏科由八個類群（七種類及一可疑變種）所組成，具有75%的高特有率。除了Cyathea walkerae和C. gigantea外，其他種類在該國均為地理上孤立分布的有限族群。所幸，所有斯里蘭卡的桫欏屬植物均出現在濕地保護區的範圍內。然而，目前已進行移地保育的物種卻相當有限，僅C. walkerae和C. crinita被保育於Hakgala的植物園中。儘管該科已是被列入華盛頓公約附錄II物種，在斯里蘭卡其各種類尚未依紅皮書的標準加以評定。因此，鑑定斯里蘭卡桫欏屬植物的特性及其受威脅程度為主要的優先事項，其次為監測分布於濕地保護區的種群；移地保育珍稀的桫欏屬種類，並以孢子進行培養也是優先的保育措施。斯里蘭卡當局應發展一個強固的計畫與國家植物標本館合作，探索在森林區塊中鮮為人知的潮濕地帶，以提升對桫欏屬植物的知識。這些資料將為該國在樹蕨保育及管理計畫的準備工作提供有力的依據。

Diversity, phytogeography and conservation status of Sri Lankan tree-ferns are discussed in this paper. The family Cyatheaceae is represented by eight taxa (seven species and one doubtful variety) in Sri Lanka with a high rate of endemism of 75%. Apart from Cyathea walkerae and C. gigantea, the other species are restricted to geographically isolated areas in the country with limited population sizes. Fortunately, all Sri Lankan species of Cyathea occur within the protected areas of the wet zone. However, ex situ conservation is limited to C. walkerae and C. crinita at Botanic Gardens in Hakgala. Despite the family being listed in Annex II of CITES, its species have not yet been assessed in Sri Lanka for the Red Listing criteria. Identification of the nature and level of threat to Sri Lankan Cyathea species is therefore a major priority, followed by the monitoring of populations in situ in protected areas in the wet zone. Ex situ conservation of rare species and cultivation of Cyathea species from spores have also been identified as priority areas. A strong programme should be developed with the National Herbarium to explore little known forest patches in the wet zone to enhance our knowledge of Cyathea species in Sri Lanka. Such information will provide a strong basis for preparing a conservation and management plan for tree-ferns in the country.