Letter | Published:

Effect of Supernumerary Chromosomes on Sex Ratio in Calligrapha philadelphica L. (Coleoptera: Chrysomelidae)

Nature volume 204, page 605 (07 November 1964) | Download Citation



SUPERNUMERARY chromosomes occur sporadically in plants and animals. In the animal kingdom, they have been observed in at least 50 insects and two turbellarians, and they may be present or absent in different populations of the same species1. They are generally considered to be inert as they are usually heterochromatic and their carriers are not distinguishable morphologically. The chromosomal polymorphism that they confer on some populations suggests that they play an adaptive part in the success of the population1,2. In plants supernumerary chromosomes have a harmful effect on vigour and fertility, and the effect becomes more pronounced as their number increases3. The work of Lewis4 and Fröst5 has suggested that their presence may be an adaptation to arid regions3.

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  1. 1.

    , Animal Cytology and Evolution (Cambridge University Press, 1954).

  2. 2.

    , J. Heredity, 47, 157 (1956).

  3. 3.

    , Proc. Tenth Intern. Con. Gen., Montreal, 1, 453 (1958).

  4. 4.

    , I.U.B.S. Symposium on Genetics of Population Structure, Pavia, 1953, 114.

  5. 5.

    , Hereditas, Lund, 44, 112 (1958).

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  1. Entomology Research Institute, Canada Department of Agriculture, The K. W. Neatby Building, Ottawa, Ontario.



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