Unexpectedly High Levels of Genetic Variation in Potentilla argentea L. (s. l.) in Southern Sweden

Abstract

Forty populations of Potentilla argentea L. (sensu lato) from southern Sweden were investigated to determine the pattern of genetic variation. Since the diploid form of Potentilla argentea has been reported to produce seeds apomictically, the intention was, in particular, to investigate whether the variation pattern indicated a purely asexual mode of reproduction in nature. The investigated populations were chosen to represent the diploid form of Potentilla argentea. Nevertheless, sympatry between diploid and hexaploid forms was found in 14 out of 40 populations sampled. Two samples contained only hexaploid plants, and 24 only diploid plants. The ploidy level was determined by chromosome counting or by morphological analysis of greenhouse grown plants. The mean number of leaves was higher and the size of the largest leaf was greater in hexaploid than in diploid offspring plants grown in the greenhouse. Among the diploids, significant variation was found for both traits between populations as well as within populations. Genetic variation was also detected with the RAPD method. To work, the method required a number of modifications of the standard protocol for DNA-purification, but it then gave clear and reproducible results. The RAPD variation was evenly distributed within and among the investigated diploid populations. The level of variation was comparable to the level found in selfing plants, but the pattern of variation was more as expected from outbreeding plants. The conclusion is drawn that Potentilla argentea may well have a variable breeding system. In nature, it does not, however, behave in a predominantly asexual manner.