Genome size variation and plant systematics

The importance of genome size, as a useful taxonomic marker, has been stressed in many studies based on different groups. A critical appraisal of intraspecific variability reported in various species so far shows that the plant genome is fairly stable (taking a narrow species concept) and is one of the salient features defining a biological species. Large differences in DNA amounts may exist at the infrageneric level which may be correlated with various adaptive traits at nuclear, cellular, tissue and organismic levels. Therefore, being an adaptive character, a comparison of nuclear C-values in conjunction with other characters may provide a natural way to elucidate evolutionary relationships. In a number of cases it is possible to study whether gain or loss of DNA has occurred during speciation which may coincide with the existing taxonomic treatment and presumed evolutionary relationships within a narrow taxonomic group. The present account deals with many recent examples which highlight the importance of genome size in microsystematics. (C) 1998 Annals of Botany Company.