Comparative analysis of the within-population genetic structure in Prunus avium L. at the self-incompatibility locus and nuclear microsatellites

Hamburg

2005

S. 99-116

3 Abb., 4 Tab.

Artikel aus einer ZeitschriftUnselbständiges Werk

200128315

Gametophytic self-incompatibility (SI) systems in plants exhibit high polymorphism at the SI controlling S-locus because individuals with rare alleles have a higher probability to sucessfully pollinate other plants than individuals with more frequent alleles. This process, referred to as balancing selection, is expected to shape number, frequency distribution, and spatial distribution of self-incompatibility alleles in natural populations. We investigated the genetic diversity and the spatial genetic structure (SGS) within a Prunus avium population at two constrasting gene loci: nuclear microsatellites and the S-locus. The S-locus revealed a higher diversity (15 alleles) than the eight microsatellites (4-12 alleles). The evenness of the allele frequency distributions was higher for the S-locus (E = 0.91) than for the SSRs (0.48 < E < 0.83), but the observed differences in the frequency of S-alleles differed significant from the expected equal distribution. A weak but significant SGS was found for the multilocus average of the microsatellites and for the S-locus, but not differences in the extent of SGS between these locus types could be ascertained. Using the multilocus SGS of the microsatellites for an indirect estimation of gene dispersal provides a neighborhood size of Nb = 130 individuals, and an average gene dispersal of σg = 106 m. Comparing this indirect measure with a previous paternity study on pollen dispersal shows that the effective pollination neighborhood is much smaller (~ 48 individuals) than the total gene dispersal neighborhood. Hence, a wider range of seed dispersal is independent on the SI system, we suppose that balancing selection on the level of our local population is counteracted by seed dispersal and other ecological processes. Therefore, the observed higher diversity at the S-locus is suggested to have existed prior to the founding of the population, and an equal distribution of S-alleles might never be reached at the level of our local population.