DNA amounts of angiosperms from the Antarctic and South Georgia

The 4C DNA amounts of 23 native or alien angiosperms from South Georgia, or the maritime Antarctic, ranged from 1.4 to 80.5 pg (in 14 monocots) and from 1.3 to 44.3 pg (in 9 dicots). These values are within the ranges previously reported for these classes, but at their lower ends. It is suggested that the maximum DNA amount per nucleus and per diploid genome for angiosperms decreases with increasing latitude (and decreasing temperature) at high latitudes. Two contributory causes of this cline are suggested. First, compared with species with lower DNA amounts, species with high DNA amounts have inordinately long minimum generation times when grown at 0–5°C and hence may be relatively poor competitors with reduced stress tolerance at low temperatures. If so, there would be a tendency for selection against species with high DNA amount. Second, DNA amount and minimum generation time are positively correlated so that the maximum DNA amount permitting establishment within a single growing season probably decreases as the duration and/or mean temperature of the growing season decreases. If so, there is an absolute selection against species with high DNA amounts which cannot establish. The roles of DNA C-value and polyploidy, in adaptation to, and pre-adaptation for, survival in cold environments are discussed.