Gynodioecy in Plantago lanceolate L. V. Frequencies and spatial distribution of nuclear and cytoplasmic genes

Abstract

In an old dune grassland the spatial distribution of male sterility type MS1 of Plantago lanceolata was found to be very patchy with spot sizes of generally less than ten square metres. Plants were collected, one per 400 square metres, over a seven hectare area and crossed as males to MS1 plants of known genotypes. Progeny analysis of these crosses and the raising of seed samples, collected from open-pollinated male steriles and hermaphrodites, allowed estimation of the frequencies of nuclear and cytoplasmic male sterility genes. Averaged over the area examined, the recessive and dominant MS1 nuclear genes occurred in frequencies of 0·98 and 0·92 respectively, while the frequency of sterile cytoplasm R was only 0·06. Locally, in and near the MS1 spots, cytoplasm R frequency was higher than average, up to 0·39, and the frequency of the nuclear sterility alleles significantly lower. The MS1 spots probably originated because of both the migration of cytoplasm R individuals into the population and a very low seed dispersal rate. The average as well as the local frequencies of nuclear and cytoplasmic genes can be explained by fitness differences between genotypes, that are associated with the evolutionary conflict between nuclear and cytoplasmic genes.