Genetic structure of a population sample of apomictic dandelions

Abstract

In Northern Europe, dandelion populations consist solely of triploid or higher polyploid apomicts. Without a regular sexual cycle or lateral gene transmission, a clonal structure is expected for Taraxacum apomicts, although this was not found by compatibility analysis. In this study, we investigate whether this observation could be suported by performing independent tests based on data from hypervariable microsatellite markers as well as more conservative data based on allozymes and matrilinear cpDNA markers. In addition, population genetic methods were used to test departure from panmictic expectations, which is expected for clonal populations. Results indicated that many data sets, again, did not agree with expectations from clonal evolution because only small groups of genotypes exhibit no marker incompatibility. Population genetic analysis revealed that virtually all genotypes, but not individuals, agreed with random segregation and genotypic equilibria. Exceptions were genotypes with rare allozyme alleles or nearly identical microsatellite genotypes. Consequently, a population sample of apomictic dandelions essentially harbours genotypes that resulted from segregation and/or recombination and only a few genotypes that may have differentiated by somatic mutations.

Clonal structure and reduced diversity of the invasive alien plant Erigeron annuus in Lithuania

“…The lower genetic diversity of some invasive plant populations has been shown with molecular markers such as ITS [8], RAPD [9][10][11] and ISSR [11][12][13][14]. In contrast, rather high genetic diversity has been shown in populations of the apomictic invaders Taraxacum, as revealed with AFLP markers [15], and Erigeron annuus, as revealed using RAPD and AFLP [16,17] markers. Five different clones were revealed in Chinese populations of Eichhornia crassipes with RAPD, and each population consisted of at least three clones [18].…”

“…This region was represented by only three populations (PN25, 26,28). The central region was represented by eleven populations (PN2, 4,13,14,15,18,20,22,23,24,29). In the southern (especially south-eastern) region of Lithuania, there are many locations that are occupied by this invasive species or where it is otherwise very frequent.…”

Male sterility in triploid dandelions: asexual females vs asexual hermaphrodites

“…Meirmans (2005) found that although clonal lineages differed from each other in seed production, they did not differ in their habitat, measured by the vegetation growing around the individuals. It is therefore uncertain whether the high clonal diversity that is generally found in dandelions (Van der Hulst et al, 2003) is maintained by Frozen Niche Variation.…”

“…Genotyping DNA-extraction, microsatellite-amplification and chloroplast PCR-RFLP were all performed using the protocols described in Van der Hulst et al (2003). Four microsatellite loci were used for genotyping the plants: msta64, msta72, msta78 and msta85 (Falque et al, 1998).…”

“…Dosage effects were clear in most of these cases; in the few cases that were ambiguous, the third allele was scored as 'missing data'. Three regions of the chloroplast genome, known to contain length and restriction-site variation in dandelions ( Van der Hulst et al, 2003), were amplified using universal primers: intron trnL (Taberlet et al, 1991) cut with Bste2, trnL-trnF (Taberlet et al, 1991) and psbAtrnH (Dumolin-Lapeque et al, 1997) cut with Dra1 and Ssp1. All chloroplast variation was scored from agarose gels, except the length variation at the psbA-trnH intergenic spacer, for which labeled primers were used and which was run on the Li-Cor.…”