Structure and dynamics of natural populations of polyploid trilliums. I. A tetraploid species T. apetalon Makino.

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  • HAGA BY Tutomu
    Department of Biology, Faculty of Science, Kyushu University
  • UCHINO Akinori
    Department of Biology, Faculty of Science, Kyushu University Department of General Education, Kumamoto University
  • WATANABE Hiroshi
    Department of Biology, Faculty of Science, Kyushu University Biological Laboratory, Kumamoto University of Commerce

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  • 倍数種エンレイソウ自然集団の構造と動態-1-四倍種エンレイソウ〔英文〕
  • バイスウシュ エンレイソウ シゼン シュウダン ノ コウゾウ ト ドウタイ 1
  • I. A tetraploid species <i>T. apetalon</i> Makino

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Karyotypes of T. apetalon (4x=20, SSUU) were analysed by the patterns of H-segments, which were revealed by cold treatment of the chromosomes. The types revealed in a given chromosome were numbered, e.g., A1, A2, A3 in chromosome A, etc. The karyotypes of individual plants were described according to a system exemplified by 3 plants from the Fujinosawa population (Fj), where the slash mark separates homoeologous pairs and the decimal mark homologous chromosomes:<br> Karyotype A B C D E Freq.<br> 6 1•1/3•3 7•7/6•6 5•5/2•2 2•2/5•5 5•5/4•4 1<br> 12 1•1/3•3 7•7/6•6 6•6/4•4 2•2/5•5 10•10/4•4 3<br> 38 1•1/3•3 7•7/6•6 5•6/2•4 2•2/5•5 5•10/4•4 1.<br> In Fj21 different homokaryotypes (32 plants), and 17 different heterokaryotypes (18 plants) with 1-3 heteropairs were identified among 50 plants examined, as in part presented in the above tabulation. Karyotypec structure of the other 3 populations was quite similar to the case of Fj. And the frequency of homozygosis of 10 pairs of homologous chromosomes was high in four different populations, ranging in percentage from 95.7 (Fj) to 99.6 (Mi- nakamidani, Mn). These high percentages indicate that reproductions is overwhelmed by selfing. Occasional outcrossing results in heterokaryotype, e.g., hybridization between karyotype 6 and 12 in Fj produces karyotype 38. Selfing of this heterokaryotype results in 6 recombinant and 2 parental homokaryotypes. Of the 6 recombinant types 3 homokaryotypes were actually observed, i.e., 7 1•1/3•3 7•7/6•6 5•5/4•4 2•2/5•5 5•5/4•4 4<br> 9 1•1/3•3 7•7/6•6 6•6/2•2 2•2/5•5 5•5/4•4 1<br> 16 1•1/3•3 7•7/6•6 6•6/5•5 2•2/5•5 5•5/4•4 2<br> The process mentioned above, i.e., occasional outcrossing followed by selfing, is the mechanism that explains how the population has become an assemblage of various homokaryotypes. With respect to all the chromosomes, A-E, four members successfully partitioned into a pair of homoeologous chromosomes, homologous chromosomes Present address : 1) Chikushino-danchi 16, Futsukaichi, Chikushinoshi 818. 2) Department of General Education, Kumamoto University, Kumamoto 860. 3) Biological Laboratory, Kumamoto being homozygous in 95-99 percent of the pairs. This is a reasonable result of the existence of various chromosome types or chromosomal variations in the diploid progenitors SS and UU, both of which are now extinct.

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