臺灣產鱗毛蕨屬稀羽亞屬(鱗毛蕨科)植物分類研究

Abstract

鱗毛蕨屬植物(Dryopteris)由於形態上的相近常造成分類之困難，歷來學者對臺灣產本屬植物之分類處理頗為分歧。其中，稀羽亞屬(Nephrocystis)內之各類群形態更是相近，且個體變異範圍頗大，時常造成分類上的問題及困難。本研究針對臺灣產本亞屬植物之葉、鱗片等外部形態特徵進行觀察，並與模式標本或相關文獻進行詳細比對，另檢視孢子囊內所含孢子數及其形態，再結合生態與地理分布資訊對臺灣產鱗毛蕨屬稀羽亞屬植物進行分類研究；此外，另利用trnL UAA (5’-Exon) -trnF、rps4-trnS等二葉綠體DNA片段之序列資料建構親緣關係樹，與形態分類一同比較，以探討臺灣產本亞屬植物之分類問題及其起源之可能性。 根據形態特徵將臺灣產本亞屬植物處理為5個物種，分別為D. cacaina、D. melanocarpa、D. sparsa、D. subexaltata及D. yoroii。其中，根據形態及分子證據認為過去分類位置不清之D. yoroii應納入本亞屬，並將以往被併入D. sparsa的D. cacaina及D. melanocarpa再度列為獨立之物種。根據分子資料建構的親緣關係樹，顯示D. melanocarpa、D. subexaltata被歸於D. sparsa的分支之中，但各自形成支持度甚高之獨立分支；而D. sparsa於臺灣的變異甚多，且分支間之遺傳距離高，分子親緣關係顯示D. melanocarpa及D. subexaltata可能是來自廣泛分布的D. sparsa之祖先。Dryopteris subgenus Nephrocystis was long considered to be taxonomically difficult because of very close interspecific similarity in morphology. In this study, the subgenus Nephrocystis is taxonomically revised based on morphological, palynological, geographical, ecological and molecular studies. Morphological characters including scales, fonds and spores were examined. Spore number per sporangium was also counted to infer reproductive mode.Furthermore, the sequences of two cpDNA fragments (trnL UAA (5’-Exon)-trnF, rps4-trnS) were used as molecular marker to reconstruct phylogenetic tree. According to morphological characters, 5 species are recognized in this subgenus. Both morphological and molecular evidences support that D. yoroii, which status was not clear previously, should be included in this subgenus. D. cacaina and D. melanocarpa, previously treated as synonym of D. sparsa, are recognized as distinct species here. The phylogenetic tree shows that D. melanocarpa and D. subexaltata formed independent clade respectively with high bootstrap value, and both are grouped into D. sparsa clade. Based on phylogenetic tree reconstructed by molecular data, D. melanocarpa and D. subexaltata were inferred to be originated from D. sparsa.