イソギクChrysanthemum pacificum NAKAI(2n=90)の分布の生態遺伝学的研究

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タイトル別名
  • イソギク Chrysanthemum pacificum NAKAI 2n 90 ノ ブンプ ノ セイタイ イデンガクテキ ケンキュウ
  • Ecogenetic Studies on the Distribution of Chrysanthemum pacificum NAKAI (2n=90)

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抄録

1)イソギクChrysanthemum pacificum NAKAI (2n=90)について,生育地の実地調査をおこない,その地理分布上の特質を生態遺伝学的に研究しようとした。2)イソギクは分布区域を,銚子-鳥島-佐倉をむすぶ地域(北緯30°28'-35°48',東経139°09'-140°50')にもつ海岸性の本邦固有種である。イソギクの種集団は,銚子・房総・三浦・伊豆・興津・用宗・御前崎・伊豆諸島の8小集団に分けらる。この小集団間の地域には本種は分布していない。したがつてこの種集団には地理的隔離の現象がみられる。3)イソギクの植生を生態および形態的見地から分けると,海岸型・海浜型・平地型・山地型の4となり,海岸型のものが主であること,および海蝕崖では他種に対し優占的であることが明らかになつた。4)房総・伊豆両半島の個々の地点における植生量測定の結果は第3,4図に示すごとくである。イソギク生育地の全長は約471,755m,巾は約3m,その植物休の草丈は約0.5mであるから,本種の地上部の全植生量は3者の相乘積7076,325m^3となる。5)本種の分布の中心は三浦・房総両半島の南部地域と推定される。

1. The aim of this paper is to illustrate the ecogenetic character of the geographical distribution of Chrysanthemum pacificum NAKAI (2n=90), inquring actually into the regions in which the plants are growing. 2. The decaploid is one of the endemic species growing on the Pacific coast of south-east Japan. It is found in the area lying about lat. 30°28'-35°48' N., and long. 139°09'-140°50' E. The north and east limits are found at Choshi (Chiba prefecture), the south limit at Torishima (Izu islands), and the west limit at Sakura (Shizuoka pref.). 3. The species population of the decaploid is divided into the following groups: the eight small populations of Choshi, Boso, Miura, Izu, Okitsu, Mochi-mune, Omaezaki, and Izu Islands. Between these, the vegetation of the species is discontinuous. The geographical isolation, therefore, is found in this species population. 4. From the ecological and morphological point of view, the vegetation of the species will be of the following types: rocky-coast, sandy-coast, field, and mountain types. The first is the commonest and stablest among these types. On the rocky-coast (sea-cliff) of south-east Japan, Ch. pacificum is dominant over the other species of vascular plants. 5. The length of the growing portion of the plant is about 471,755m, the width of it is about 3m, and the height of the plant-body is about 0.5m. Thus the total vegetation volume of the species population is demonstrated by 7076,325m^3, which is the continued product of the above-mentioned values. 6. It is estimated that the south areas of Boso and Miura peninsulas form the center of the distribution of Ch. pacificum.

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