蛇菰屬三藥蛇菰亞屬植物之系統分類研究

Abstract

蛇菰科蛇菰屬 (Balanophora)植物為無葉綠素的根寄生植物，蛇菰藉由吸器汲取寄主養分及水分，花序在花期時才會從吸器抽長出來。蛇菰的花部器官十分退化，雄花僅具一輪花被片以及不具花絲的聚藥雄蕊，雌花更是只剩雌蕊一個器官著生在花序軸或是附屬物基部。蛇菰屬其下可分為蛇菰亞屬 (subgenus Balanophora)及三藥蛇菰亞屬 (subgenus Balania)。 根據先前研究所建構蛇菰屬內的分子譜系樹，確認過去被歸入三藥蛇菰亞屬中具無配生殖的日本蛇菰 (Balanophora japonica)是蛇菰亞屬疏花蛇菰 (B. laxiflora)的近緣種，也確認三藥蛇菰亞屬是一具高支持度的單源類群，但使用此亞屬分析的材料僅包含臺灣產之海桐生蛇菰 (B. tobiracola)與紅冬蛇菰族群 (B. harlandii)，而大陸地區所產的紅冬蛇菰族群、筒鞘蛇菰 (B. involucrata)、川藏蛇菰 (B. fargesii)及杯莖蛇菰 (B. subcupularis)並未納入探討。 為了釐清本亞屬類群的分子譜系關係並比較其細部分類特徵，本研究針對三藥蛇菰亞屬植物之雌花序及花粉形態，利用掃描式電子顯微鏡(SEM)觀察，並以部分18S rRNA與ITS序列建構譜系樹進行系統分類的探討，亦抽取寄主根部DNA分子資料以鑑定寄主。B. harlandii其分類歷史有許多同物異名被發表，不同族群之間亦存在種內變異；分子證據結果顯示原B. harlandii為多系群，我們重新對各分支定名，分別是模式標本產自香港的紅冬蛇菰 (B. harlandii)、臺灣產的筆頭蛇菰 (B. mutinoides)以及一未定名蛇菰 (B. sp.)，而該種需要更多模式標本檢視以及雄花形態才能予以定名。川藏蛇菰及筒鞘蛇菰都是苞片基部相連成鞘狀的類群，在分類歷史上有數次整併或分離，兩者之差別在於性別表現不同，根據其花粉及附屬物等細微構造，發現兩者並無太大差異，分子證據則支持兩者為非常相近但不同分支的姊妹群，本研究暫時將此二名保留，但不另外處理這兩種的學名位階。海桐生蛇菰學名一直以來有兩個拉丁名混用的情形，根據發表文獻我們認為B. wrighti是裸名，應該使用B. tobiracola。而以往曾被分類至三藥蛇菰亞屬的杯莖蛇菰 (B. subcupularis)，依據花被片多為4數、花粉具孔的蛇菰亞屬特徵以及分子證據，支持杯莖蛇菰歸入蛇菰亞屬中。 根據本論文研究，雌花著生位置不能單獨作為區分亞屬的特徵，因此我們限縮亞屬的定義：蛇菰亞屬花被片4數以上、有花粉孔、三藥蛇菰亞屬花被片3數、無花粉孔，然而對於無配生殖的蛇菰尚無界定亞屬的特徵。 寄主的分子鑑定結果顯示筆頭蛇菰之寄主為五列木科紅淡比屬植物；紅冬蛇菰之寄主為豆科之雞血藤屬植物；未定名蛇菰之寄主為八仙花科之繡球花屬植物；川藏蛇菰為無患子科之楓屬、小蘗科之小蘗屬、楊柳科之柳屬、杜鵑花科之杜鵑花屬、五味子科之五味子屬植物；海桐生蛇菰之寄主為木犀科植物；筒鞘蛇菰之寄主為薔薇科李屬植物、杯莖蛇菰之寄主為衛矛科南蛇藤屬和無患子科之楓屬植物。

Balanophoraceae is a root parasitic plant without chlorophylls. Balanophora is the largest genus in Balanophoraceae, which had been divided into two subgenera, Balanophora and Balania. The first phylogenetic analysis of Balanophoraceae showed that, the agamospermic B. japonica is confirmed to be allied to B. laxiflora, which was treated under subgenus Balania taxa. In addition, the subgenus Balania species formed a monophyloetic clade with a high support. However, only two Balanophora subgenus Balania taxa B. tobiracola and B. harlandii from Taiwan in previous study were sampled, and others members such as like B. fargesii, B. involucrata, B. subcupularis and population of B. harlandii in China were not included. The aims of this research are to study the phylogenetic relationships of subgenus Balania with more complete sampling, and also to examine their micro-morphological (spadicle top surface and female flower adhering area) and palynological characters. The results from phylogenetic analysis and different micro-morphological characters, phenology and attitudinal distribution showed that B. harlandii samples is polyphyletic. According to their morphology and phylogeny, the separate bracts and diecious Balanophora harlandii should be treated as B. harlandii, B. mutinoides and a unknown species B. sp.. B. fargesii and B. involucrata are bracts sheath-like taxa formed a highly supported clade, and micro-morphological characters also showed high similarity, but due to their different sexual expression, we treated its as different taxa. Balanophora subcupularis is obviously different from all other subgenus Balania taxa by its micro-morphological characters, and the result of phylogenetic tree showed that B. fungosa it is sistered. Hence, B. subcupularis should be restated and treated under the subgenus Balanophora. In this study, we redefine the characters of two subgenus. Male flower 3-merous, pollen inaperture in subgenus Balania, male flower 4-merous above, pollen aperture in subgenus Balanopohra. In addition, we applied DNA barcoding technique to identify the host of Balanophora. According to the result, the confirmed hosts of B. mutinoides is Cleyera sp. (Pentaphylaceae), the host of B. harlandii is Callerya sp. (Fabaceae), the host of B. sp. is Hydrangea sp. (Hydrangeaceae), the hosts of B. fargesii include Acer sp. (Sapindaceae), Berberis sp. (Berberidaceae), Rhododendron sp. (Ericaceae) ,Salix sp. (Salicaceae), Schisandra sp. (Schisandraceae), the host of B. involucrata belongs to Oleaceae, the host of B. subcupularis are Acer sp. (Sapindaceae) and Celastras sp. (Celastrasceae).