Unequal morph frequencies in populations of tristylous lythrum salicaria (Lythraceae) from southern sweden

Abstract

Style morph frequencies in tristylous Lythrum salicaria were determined along the shore of a lake in South Sweden. The results indicated a significant deviation from equal morph frequencies, with the S morph having a lower frequency than the L morph and the M morph being intermediate but there was no tendency for the S morph to be subject to local loss more frequently than the other morphs, as would be expected if genetic drift were responsible for the deviation seen at the regional level. The linear distribution of the habitat and the presence of all three morphs even in small clusters of plants indicate extensive gene flow with seedlings recruited from the same pool of water-dispersed genotypes. Morph-specific differences in fitness or self-fertilization may be more important than random processes in determining morph frequencies in this region and in other areas with a similar population structure. © 1994 The Genetical Society of Great Britain.