| Summary: | 碩士 === 國立臺灣大學 === 生態學與演化生物學研究所 === 101 === 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.
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