| Summary: | 博士 === 國立成功大學 === 生命科學系碩博士班 === 98 === Onagraceae are widely distributed in the world, which include about 7 tribes, 17 genera, and 652 species. Genus Ludwigia are widely distributed in wetlands of tropical and temperate regions in the world, which include 23 sections and 81 species. The section Microcarpium has 14 species, all are mainly in ES of U.S.A. excepting that L. stricta is endemic to Cuba. All species of Ludwigia section Microcarpium grow at wetlands, including habitats of shallow ponds, lakes, creeks, lagoons, marshes, humid ranches grasslands, drains, agricultural ditches, and wetlands in forest.
This research uses all of the 14 species in Ludwigia section Microcarpium, doing the phylogenetic relationship analysis by using the chloroplast DNA atpB-rbcL, the sequence of noncoding spacer, and the sequence of Internal Transcribed Spacer (ITS) of the ribose DNA (nrDNA) of cell nucleus. The result of ITS analysis shows that, excepting that L. stricta cannot be analyzed, the phylogenetic relationship of the rest of the 13 species can be divided into two main groups. The first one consists of tetracarpa taxon (L. alata, L. sufruticosa, and L. lanceolata), a new species L. pseudoalata, and L. pilosa complex (L. pilosa, and L. ravenii). Analysis data shows that L. pilosa and L. ravenii are two differentiated taxa, but with close parental relationship. The second one consists of the rest of species, and the following results concluded: (1) L. polycarpa, L. glandulosa taxon, and petalous group (L. linearis, L. linifolia) are significantly differentiated. Analysis also shows that L. glandulosa, and its subspecies L. glandulosa ssp. brachycarpa should have already differentiated. (2) The complicate relationship between L. sphaerocarpa and other species shows that this species should be the origin of hybridization, and has complicate gene flow with other species. (3) The L. microcarpa in microphyllum group is significantly differentiated from the other two species of the same group -- Ludwigia curtissii and L. simpsoni, which might be the same species。
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