Ribosomal DNA variation among populations of a Pinus rigida Mill. (pitch pine) ecosystem. I. Distribution of copy numbers
1992
Govindaraju, D.R. | Cullis, C.A.
We determined the number and distribution of rRNA genes among individuals of eight pitch pine populations representing a small ecosystem. While these populations show little or no variation for allozymes and also experience high gene flow, they exhibit large amounts of morphological diversity, apparently caused by environmental stress. Nine to ten contiguously distributed individuals, located approximately at the centre of the plots in seven out of eight populations, were used toward determining copy numbers. These ranged from 355 to 7356. Approximately, a 12-fold variation among individuals within populations, and 21-fold variation between the lowest and the highest values, among populations was recorded. Numbers of rDNA copies were found to be lower among populations subjected to environmental stress. We conclude that strong diversifying selection may influence the abundance of rRNA genes among pitch pine populations.
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