FLUCTUATING ASYMMETRY IN CENTRAL AND MARGINAL POPULATIONS OF LYCHNIS-VISCARIA IN RELATION TO GENETIC AND ENVIRONMENTAL-FACTORS

Developmental instability in the form of increased fluctuating asymmet ry can be caused by either genetic or environmental stress. Because ex tinctions can be attributed broadly to these factors, fluctuating asym metry may provide a sensitive tool for detecting such stresses. We stu died the level of fluctuating asymmetry of flowers of a perennial outc rossing plant species, Lychnis viscaria, both in natural and common-ga rden populations. The degree of flower asymmetry was higher in small, isolated, and marginal populations of the species range. These margina l populations also were the most homozygous. In the core area of the s pecies' range, flowers were more symmetrical. The level of asymmetry w as correlated with both population size and heterozygosity. However, a partial correlation analysis revealed that when the impact of populat ion size was controlled for, there was a negative relationship between fluctuating asymmetry and heterozygosity, whereas when controlling fo r heterozygosity, no relationship between population size and fluctuat ing asymmetry was found. This indicates that genetic consequences of s mall population size probably underlie the relationship between the le vel of asymmetry and population size. Results from a transplantation e xperiment showed that individuals subjected to a higher environmental stress had an increased level of asymmetry compared to control plants. In the common-garden conditions the level of fluctuating asymmetry di d not differ between the central and marginal populations. This sugges ts that presumably both genetic and environmental factors affected to the higher level of asymmetry among marginal populations compared to c entral ones. In all, we conclude that even though fluctuating asymmetr y seems to be a sensitive tool for detecting stresses, results from st udies focusing on only one factor should be interpreted with caution.