| Summary: | 碩士 === 臺灣大學 === 生態學與演化生物學研究所 === 95 === The enlarged and showy calyx lobes of the species of Mussaenda (Rubiaceae), have been known to attract pollinators. Variations on the size and color of Mussaenda species in Taiwan were observed, but the significance was unknown. In current taxonomic treatment by the second edition of the Flora of Taiwan, only one species was recognized in the island of Taiwan - Mussaenda pubescens Aiton. Based on the morphological observation, two forms of Mussaenda species can be found, one is mostly distributed on the northern part of Taiwan, another towards the southern part of Taiwan. The northern populations are congruent in the description of a previously recognized taxon, M. taihokuensis Masam., in having small calycophylls, and they show no sign of reproductive failures since they still set fruits in the field. Further examination shows that this northern form of Mussaenda has lighter petal color and shorter corolla tube than the southern form; and both northern and southern populations of Mussaenda have equal length of calyx teeth and calyx tube, which is incongruent with the description of M. pubescens.
Phylogenetic analyses were conducted based on nrITS and chloroplast trnT-F spacer and the results show that all sequenced individuals in Taiwan are grouped with M. parviflora Miq. and M. shikokiana Makino, and distinct from M. pubescens collected in Hong-Kong. Moreover, our data from crossed-pollination experiments for the northern and southern forms show that the crossed flowers cannot set fruits, indicating that these two forms have developed reproductive isolation even they can co-exist in the field. Based on all the results, the commonly seen Mussaenda species in middle and southern part of Taiwan should be named M. parviflora and the ones in northern part of Taiwan should be better named M. taihokuensis.
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