澀葉榕亞屬（桑科，榕屬）葉片結構性狀在系統分類與生態的意義

Leaf structural traits of the subgenus Sycidium (Ficus, Moraceae) and their significance in classification and ecology

葉片結構性狀具相對穩定性，可反映植物於不同環境中的適應對策，對於探討植物分類學、生態學等研究已被廣泛運用。本研究以葉面積、葉乾重、比葉面積、葉片厚度、葉片解剖構造.、氣孔長度及密度、毛狀物長度等葉片結構性狀，探討臺灣產桑科榕屬澀葉榕亞屬6分類群的分類及其生態適應表現。結果顯示，澀葉榕節與古榕節在葉片厚度、柵狀組織、海綿組織及氣孔密度等葉結構性狀具顯著差異。葉結構性狀的主成分分析結果顯示，大多物種在排序圖聚集成群，而古榕節的物種組成間較澀葉榕節分布，可能顯示後者分布的生育地環境較多樣。主成分分析排序圖第1軸主要受柵狀組織與海綿組織厚度、上表皮層數和下層表皮厚度等特徵分化，而第2軸主要受上表皮厚度與氣孔長度的影響。尖尾長葉榕比葉面積最高，反應其半附生的生長型，以及生長在林下的環境，透過擴大葉片面積來獲取更多光照資源的特性。斯氏榕的葉片最厚，氣孔密度最高，反應其濱海高位珊瑚礁岩的環境。比較共域生長的澀葉榕與金氏榕葉片結構性狀發現，金氏榕藉由增加葉片組織密度，來抵禦不良的環境因子；澀葉榕的葉面積和比葉面積較大，有助其攫取更多光照資源，增加光合效率，顯示相同生活型的近緣種在共域環境下採取不同的生存適應對策。綜合上述結果，葉片結構性狀在探討澀葉榕亞屬分類與生態特性具有良好的解釋。

The relative stability of leaf structural traits (LSTs) reflects the adaptability of plants in different environments, therefore it is useful in the studies of plant taxonomy and ecology. In this study, LSTs, including dry weight, leaf area, specific leaf area (SLA), composition of the transverse section of the lamina, stomatal density and length, as well as lengths of lithocysts and trichomes were evaluated to determine the taxonomy and ecology of six taxa of Ficus L. subgenus Sycidium (Miq.) Mildbr. & Burret in Taiwan. The results showed that LSTs such as leaf thickness, palisade tissue, sponge tissue and stomata density were significant different between the section Sycidium Miq. and the sect. Palaeomorphe King. Principal components analysis (PCA) results showed that the thicknesses of palisade tissues and spongy tissues, upper epidermal layer, and thickness of lower epidermis were significantly correlated with axis 1; while the thickness of the upper epidermis and stomatal length were correlated with axis 2. The PCA ordination plot showed that the taxa of the section Palaeomorphe King had a more scattered distribution compared to the section Sycidium Miq., indicating the former distributed in more diverse habitats. The SLA of Ficus heteropleura Bl. var. caudatifolia (Warb.) H. Y. Tzeng was the largest, suggesting that the fig tree could harvest more solar energy by enlarging the leaf area under the canopy environment. The leaf of Ficus tinctoria Forst. f. ssp. swinhoei (King) Corner was the thickest, with the highest stomatal density in the taxa of subg. Sycidium Miq. These characteristics could benefit the trees to grow in the habitats of uplifted coral reefs in the seashore. Compared with the LSTs of two sympatric fig trees between F. ampelas Burm. f. and F. irisana Elm., the former had an increased leaf tissue density to resist the adverse environment, while the latter had an increased leaf area and SLA to capture more light energy and enhance its photosynthetic efficiency. The results of of the LSTs analysis showed that the two sympatric fig species adopted different survival strategies in the same environment. The results of this study showed that LSTs are useful parameters for taxonomy and ecology research of the subgenus Sycidium Miq.