Nuclear DNA amounts in populations of Picea and Pinus species

Abstract

There are numerous reports of a very wide range of variation in nuclear DNA amounts among populations within species of the Pinaceae, including Picea glauca, the White Spruce. Our survey of 26 provenances, covering almost the entire range of White Spruce in North America showed, in contrast, no significant variation in nuclear DNA amount within the species except for minor fluctuations due to B chromosomes. The DNA estimates, throughout, fall within the range of 37·4 to 40·4 × 10−12 g. The areas of the 2C nuclei measured at G1 from 12 provenances were also highly uniform. In addition, there was no significant variation in the chromosome volume between and within provenances. Both facts reinforce the conclusion that nuclear DNA amounts within the species are constant. There are no detectable differences in the nuclear DNA content between Picea glauca and P. engelmannii. In Pinus contorta as in P. glauca, nuclear areas and DNA amounts do not vary significantly between or within provenances and the mean DNA value of 2C nuclei is 40·34 × 10−12 g. White Spruce in North America alone ranges over 3000 miles of longitude and some 1000 miles of latitude. The constancy of the nuclear DNA amounts among provenances of White Spruce and of the other species growing in widely differing environments is both surprising and impressive. It provides further testimony to the pronounced inertia to quantitative DNA change within species.