碩士 / 國立臺灣大學 / 森林環境暨資源學研究所 / 99 / V
Abstract
The Karst terrains across the Sino-Vietnamese border are known for its extremely
high plant diversity and endemism. To understand mechanisms that had generated its
remarkable biodiversity, we study patterns of genetic diversification of the
Sino-Vietnamese limestone Begonia. About 70 Begonia species are found exclusively in
the limestone habitats of the region, including all members of sect. Coelocentrum and
sect. Leprosae and four species of sect. Diploclinium. Because most of these limestone
species are poor dispersers and have narrow and restricted distributions on the highly
fragmented limestone habitats, limited gene flow might have been the major contributor
to their genetic diversification. Morphological variation of Sino-Vietnamese limestone
Begonia is mainly manifested in vegetative traits that have no apparent correlation to
their environments, implying that morphological variation could have been primarily
non-adaptive. We collected DNA sequences of two chloroplast intergenic spacers
(trnC-ycf6 and petB-petD) of 61 Sino-Vietnamese limestone Begonia species to
reconstruct their phylogenetic relationships. Mantel tests between genetic, geographical,
and morphological distances were performed for three widespread species and four
groups (clade A-D) of closely related species revealed by the phylogenetic trees. Results
show that Sino-Vietnamese limestone Begonia group forms a poorly supported clade
composed of 11 subclades. A significant positive correlation between genetic and
geographic distance was observed in both inter- and intraspecific tests except for clade
D. Correlations between morphological distance of leaf traits and genetic distance were
not significant in all tests. Correlations between leaf morphological distance and
geographic distance were also not significant in all tests. Except for clade C,
VI
correlations between floral morphological distance and genetic distance were not
significant. Correlations between morphological distance of floral traits and geographic
distance were not significant except for clade C. Based on these analyses and inferences,
the high species diversity of Sino-Vietnamese limestone Begonia appears to be results
of species radiation. Limited dispersability and geographic isolation should have played
an important role in spawning its species diversity. Morphological variation of these
limestone Begonia species appears to be resulted from natural selection, likely related to
the strong niche conservatism to their habitats.
| Identifer | oai:union.ndltd.org:TW/099NTU05359048 |
| Date | January 2011 |
| Creators | Chia-Yu Lin, 林家瑜 |
| Contributors | 鍾國芳 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 92 |
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