Genetic variability of fragmented stands of pedunculate oak (Quercus robur) in Finland.

The genetic structure of 33 natural Quercus robur stands in Finland was studied using 13 allozyme loci to analyze the effects of fragmentation in a wind-pollinated tree species. The present fragmented and discontinuous distribution of oak is a result of both short-term human impact and long-term climatic and geological change, including post-glacial land uplift. In accordance with general expectations, genetic diversity in small populations was lower than that in large populations, and differentiation among small populations was higher than that among large populations. Heterozygote deficiency was more pronounced in large populations, which is proposed to be a Wahlund effect created by either spatial sub-structuring or the existence of synchronized flowering lineages. Also genetic differentiation was higher and diversity lower in Finland than the estimates reported for Central Europe. There were differences in the genetic structure on sites of different geological age. We suggest that on most geologically old sites drift has a prominent effect whereas on younger sites also founder effects may be important.

Microsatellite sequences in a conifer, Pinus sylvestris.

Scots pine (Pinus sylvestris) genomic libraries were constructed and screened with oligonucleotides probes (GT)10, (CT)10, and (AT)10. Eight microsatellites were identified from 6000 clones screened. The longest microsatellite stretch found, (CT)9(N)21(AT)24, was amplified from bud and single pollen grain samples. In order to clarify the complex amplification pattern revealed, two PCR products were sequenced. The size differences were caused both by varying repeat numbers of the microsatellite stretches and by differences in other parts of the amplified sequence. This kind of complex molecular basis of microsatellite amplification within a species has been previously reported. Microsatellite sequences were used as PCR primers to detect polymorphisms and to estimate the abundance of microsatellites.