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Chromosome Phylogeny and Habitat Preference of Clarkia

Harlan Lewis
Evolution
Vol. 7, No. 2 (Jun., 1953), pp. 102-109
DOI: 10.2307/2405745
Stable URL: http://www.jstor.org/stable/2405745
Page Count: 8
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Chromosome Phylogeny and Habitat Preference of Clarkia
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Abstract

The original basic chromosome number of the genus Clarkia can be shown with reasonable certainty to have been 7. Subsequent change in chromosome number has involved primarily the addition of the equivalent of whole chromosomes to produce genomes of 8 and 9. A reduction in number has also occurred as a result of translocation and loss of centromere regions. Species with the original number of 7 chromosomes occupy for the most part relatively mesic sites while species with derived numbers occupy more xeric habitats. The correlation of chromosome phylogeny with ecological preference suggests that the genus may have had its origin in the more mesic aspects of an ecotone between the Arcto-Tertiary and Madro-Tertiary Floras and has subsequently spread into the more xeric derivatives of the Madro-Tertiary Flora.

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