穗花蛇菰與其近緣類群之親緣關係與其寄主研究

Phylogenetic Relationships and Associated Hosts of Balanophora laxiflora (Balanophoraceae) and Allied Taxa

謝昀臻(Yun-Chen Hsieh)

指導教授 ： 胡哲明

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.00840

摘要

蛇菰屬(Balanophora)植物為蛇菰科(Balanophoraceae)之全寄生植物，寄生於寄主植物之根部，藉由塊莖狀吸器從寄主獲取水分以及營養素。蛇菰花部器官明顯退化，雄花僅具一輪花被片與聚藥雄蕊；雌花僅具一枚極微小的雌蕊。
穗花蛇菰(Balanophora laxiflora)廣泛分布於大陸華南、越南與臺灣中海拔森林底層，為雌雄異株植物。在分類歷史上曾有許多穗花蛇菰的同物異名被發表，而不同穗花蛇菰族群之間亦存在著種內變異。穗花蛇菰之雌株與同為臺灣原生種之日本蛇菰(B. japonica)與屋久島蛇菰(B. yakushimensis)兩種雌株形態相近。日本蛇菰與屋久島蛇菰皆分布於日本南部以南至臺灣，且皆未曾有雄株之採集紀錄，而日本蛇菰確定具有無配生殖的(agamospermic)能力，加上兩者被證實與穗花蛇菰親緣關係相近，懷疑日本蛇菰與屋久島蛇菰有可能自現生穗花蛇菰分支，因具備無配生殖能力而能持續繁衍並累積變異終至種化。本研究增加穗花蛇菰之採樣數量，並使用DNA分子資料分析穗花蛇菰與其近緣物種之間的親緣關係，目的為探討其近緣物種是否由現生穗花蛇菰分支而來。同時，本研究亦探討穗花蛇菰種內變異類型是否會各自形成親緣關係中的單源群，甚或有隱蔽物種存在。
本研究結果顯示，穗花蛇菰、日本蛇菰與屋久島蛇菰各自皆為單系群，且穗花蛇菰為後兩者所形成枝序之姊妹群。從所選穗花蛇菰之種內遺傳變異來看，部份族群形成一具有高支持度的單系群，其形態同時滿足以下特徵：雄花序呈現橘色、雄花序開花區下半段之雄花呈水平長橢圓形且花被片達八片以上、雄花序開花區內之苞片裂瓣呈細柱狀且為橘色至淺黃色。然上述特徵皆為個體間之連續型變異。
在Hansen所著之蛇菰屬專論中，穗花蛇菰具有相當高的寄主多樣性。以往調查蛇菰寄主的方式，主要為循蛇菰所寄生之根往回追尋寄主，本研究之目的為運用DNA分子資料針對穗花蛇菰進行寄主鑑定至屬之層級。
根據結果，臺灣的穗花蛇菰寄主包含蕁麻科之樓梯草屬、無患子科之楓屬、桑科之榕屬和桑屬、樺木科之赤楊屬、薔薇科之懸鉤子屬、報春花科之紫金牛屬等植物。臺灣的日本蛇菰與屋久島蛇菰則呈現不同於穗花蛇菰的高度寄主專一性，分別寄生於灰木科之灰木屬和茶科之木荷屬植物。

關鍵字

蛇菰屬 ； 寄生植物 ； 親緣關係 ； 無配生殖 ； 寄主 ； 分子鑑定

並列摘要

Balanophora (Balanophoraceae) are holoparasitic, parasitizing on roots of host plants, obtaining water and nutrient from hosts with tuber-shaped haustoria. Flowers of Balanophora are highly reduced. There are only one whorl of tepals and a synandrium in the male flower. Female flower is reduced to only one extremely small pistil left for each flower.
Balanophora laxiflora is a dioecious species, distributed in southern China, Vietnam, and Taiwan, growing under the forests at intermediate altitude. There have been many synonyms of B. laxiflora published through its taxonomic history, and there are also intraspecific variations in morphology and genetics within different populations. Morphology of female B. laxiflora is similar with that of B. japonica and B. yakushimensis. Recent study also confirmed that B. laxiflora is close to B. japonica and B. yakushimensis in phylogeny. There is no male individuals found for the later two taxa, and the agamospermy of B. japonica has been confirmed in previous studies. We speculated that B. japonica and B. yakushimensis were probably derived from B. laxiflora, being able to keep breeding and accumulating variation due to their agamospermic nature. This research increases the sampling of B. laxiflora individuals, using DNA molecular data to analyze the phylogenetic relationship within B. laxiflora and the two allied taxa. The aim of the study is to examine whether the allied taxa were derived from B. laxiflora, and if there is any cryptic taxa existing.
Result of this study reveals that, in Taiwan, B. laxiflora, B. japonica and B. yakushimensis each forms a monophyletic group, and B. laxiflora is a sister group to the clade composed of the other two taxa. By analyzing the phylogenetic relationships with the chosen intraspecific genetic variation of B. laxiflora, a subset of populations form a highly supported monophyletic group. This group has all the characters as following: orange male inflorescence, horizontally elliptic male flower with eight or more tepals in the proximal flower region, and thin, narrow and orange to light yellow split bract lobes in male inflorescence. However, these are all continuous variations within B. laxiflora individuals.
In Hansen’s monograph on Balanophora, host diversity of B. laxiflora is high. In the past, the main method to identify the host of Balanophora is tracing the root, which Balanophora parasitizes on, back to its plant trunk. The aim of this research is to identify the host plants that B. laxiflora parasitizes on to genus level by using DNA molecular data.
According to the result, the confirmed hosts of B. laxiflora include Elatostema and Oreocnide (Urticaceae), Acer (Sapindaceae), Ficus and Morus (Moraceae), Alnus (Betulaceae), Rubus (Rosaceae), and Ardisia (Primulaceae). Different from B. laxiflora, B. japonica and B. yakushimensis show high host specificity to Symplocos (Symplocaceae) and Schima (Theaceae) respectively.

並列關鍵字

Balanophora ； Parasitic plants ； Phylogeny ； Agamospermy ； Host ； Molecular identification

參考文獻

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