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rbcL,matKおよびphyA遺伝子の塩基配列を用いた、 アマモ科種の分子系統学的解析、及び集団遺伝学的解析： 日本沿岸域に生息する海草の起源と多様性
https://ir.soken.ac.jp/records/1209
https://ir.soken.ac.jp/records/1209724061ae-39ed-4c63-b88c-8b1e2780a0c2
| 名前 / ファイル | ライセンス | アクション |
|---|---|---|
要旨・審査要旨 / Abstract, Screening Result (387.9 kB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2010-02-22 | |||||
| タイトル | ||||||
| タイトル | rbcL,matKおよびphyA遺伝子の塩基配列を用いた、 アマモ科種の分子系統学的解析、及び集団遺伝学的解析： 日本沿岸域に生息する海草の起源と多様性 | |||||
| タイトル | ||||||
| タイトル | PHYLOGENETIC AND POPULATION GENETIC ANALYSES OF ZOSTERACEAE SPECIES BASED ON rbcL, matK AND phyA NUCLEOTIDE SEQUENCES: Implications for the origin and diversification of seagrasses in Japanese waters | |||||
| 言語 | en | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||
| 資源タイプ | thesis | |||||
| 著者名 |
加藤, 由実子
× 加藤, 由実子 |
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| フリガナ |
カトウ, ユミコ
× カトウ, ユミコ |
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| 著者 |
KATO, Yumiko
× KATO, Yumiko |
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| 学位授与機関 | ||||||
| 学位授与機関名 | 総合研究大学院大学 | |||||
| 学位名 | ||||||
| 学位名 | 博士（理学） | |||||
| 学位記番号 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | 総研大甲第786号 | |||||
| 研究科 | ||||||
| 値 | 先導科学研究科 | |||||
| 専攻 | ||||||
| 値 | 21 生命体科学専攻 | |||||
| 学位授与年月日 | ||||||
| 学位授与年月日 | 2004-03-24 | |||||
| 学位授与年度 | ||||||
| 値 | 2003 | |||||
| 要旨 | ||||||
| 内容記述タイプ | Other | |||||
| 内容記述 | Seagrasses are composed of four families (Cymodoceaceae, Hydrocharitaceae, Posidoniaceae, and Zosteraceae) belonging to angiosperms, and are thought to have adapted independently to aquatic life. Seagrass beds are productive ecosystems; estimates of average net primary production place seagrass beds as one of the most important in the biosphere. Seagrass beds also support high biodiversity and productivity of coastal waters. Rapid losses of seagrass beds, due mainly to artificial disturbances, endanger these species and associated ecosystems<br /> The seagrass family of Zosteraceae consists of three genera: Phyllospadix, Zostera and Heterozostera. This family is distributed mainly in temperate regions of the northern and southern hemispheres. There is no record of a Zosteraceae species occuning in both hemispheres, although some species in certain subtropical and tropical seagrass families (Hydrocharitaceae and Cymodoceaceae) occur in both hemispheres. High species diversity of Zosteraceae in the Northern Hemisphere is observed around the Japan Archipelago, suggesting the family may have evolved from this region. Unfortunately, many Zosteraceae seagrass beds have disappeared from Japanese waters. For instance, it is reported that seagrass beds have declined by 4% during the thirteen-year period from 1978 to 1991.<br /> Conservation of these seagrasses requires that knowledge concerning the history and genetic variation of seagrass within and between species or local populations. To examine the indispensability of seagrass beds around the Japan Archipelago, I investigate the history and genetic diversity of Zosteraceae species from the viewpoint of population genetics. <br /> First, 2.8 kb nucleotide sequences of rbcL and matK genes of the chloroplast genome were examined to elucidate the origin and subsequent diversification of the Zosteraceae family of seagrasses. I determined the 24 rbcL and 30 matK sequences from five Zostera species (Z. marina, Z. caespitosa, Z. caulescens, Z. japonica, and Z. asiatica). Furthermore, to determine the tirne at which Zosteraceae diverged from closely related species, I used 207 rbcL and 115 matK sequences of the order Alismatales, to which the four seagrass families and other ten families belong. The rbcL sequence data cover all 14 families of Alismatales, while the matK sequence data cover seven families. Using the nucleotide sequences from family Araceae as outgroups, the number of synonymous nucleotide substitutions were examined. After confirming the validity of a molecular clock of chloroplast genes between Zosteraceae and rice, I estimated the divergence times of Zosteraceae species by applying the synonymous substitution rate of the rice rbcL gene to Zosteraceae, with the following results. <br /> 1) The estimated divergence time between Zosteraceae and its closest relative, Potamogetonaceae is approximately 100 - 133 million years (myr), placing it within the Cretaceous period. The divergence time between the genera Zostera and Phyllospadix was estimated as 36 - 48 myr. These values suggest that present Zosteraceae emerged somewhere in the peliod between 36 - 48 myr and 100 - 133 myr ago. 2) Two subgenera of Zostera - Zostera and Zosterella - exhibit monophyly and appear to have differentiated from each other approximately 33 - 44 myr ago. However, the data indicate the third genus Heterozostera branched off only 5 - 7 myr ago from the stem lineage leading to Zosterella, which appears too recent in comparison with the ancient divergence of the two subgenera. 3) I estimated the emergence time of the most recent common ancestor of the subgenus Zostera as 6 - 8 myr ago. Based on these phylogenetic analyses, I propose a provisional age-related classification of the Zosteraceae to account for their origin and evolution. 4) I also examined the extent of polymorphisms in Z. marina using rbcL and matK sequences. Four haplotypes were found in the samples, which have undergone diversification during the past 1.5 myr. One haplotype is observed among samples taken from both sides of the Japan Archipelago, and closely related haplotypes are observed among samples taken from the eastern Pacific Ocean. Although the number of samples is not large, this result suggests that a simple genetic structure cannot explain the distribution of chloroplast haplotypes in seagrasses of Japanese waters and the Pacific Ocean.<br /> Second, two seagrass species endemic to Japan and Korea, cosmopolitan Zostera marina and Z. caulescens, were chosen as a basis for population genetic analyses and from the two species I collected 29 and 10 samples, respectively. Sampling localities cover 16 and 6 local populations on both sides of the Japanese Archipelago for Z. marina and Z. caulescens, respectively. I sequenced the 1.5kb phyA gene in the nuclear genome and confirmed the suitability of the phyA gene as a molecular demographic marker with the following observations: 1) there are many segregating sites, 2) the region evolves in a neutral fashion, and 3) no recombination events were detected in the region. I then examined the genetic diversity of 58 Z. marina and 20 Z. caulescens phyA genes, focusing on population structure and the extent of gene flow among local populations. <br /> Haplotypes found in Z. marina and Z. caulescens numbered 16 and 6, respectively. Both species possess unique characteristics. Phylogenetic tree analysis reveals that the 16 haplotypes of cosmopolitan Z. marina are classified into two groups, A and B, which diverged 1.4 myr ago. On the other hand, most haplotypes in endemic Z. caulescens are specific to each local population. However, the extent of local differentiation in Z. caulescens is not as great as that between the A and B haplotype groups of Z. marina. It also appears that each population within the species has not been panmictic during the time period in which the polymorphism appears. I also found a geographical association of haplotypes, suggesting limited amounts of gene flow between local populations. However, there are a few haplotypes shared between local populations, and even between populations in the Sea of Japan and the Pacific Ocean. These observations suggest that the observed population structure of the two species could not be explained solely by gene flow due to sea currents. This analysis also suggests that local disturbance, such as extinction of local populations, is likely to destroy the total genetic diversity of seagrasses in Japan.<br /> The seagrass flora of Japan is characterized by the occurrence of several species of Zosteraceae that are considered endemic to the northwestern Pacific. Moreover, this study revealed that population structures are present in both populations or cosmopolitan Z. marina and the endemic species, Z. caulescens. The mechanism generating the genetic diversity of seagrasses around Japan is not explained by a simple unidirectional gene flow by sea currents or geographical isolation, and a destruction of this habitat may take another 1 myr to restore the present genetic diversity. | |||||
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| 値 | 有 | |||||
