Past demography in forest trees: what can we learn from nuclear DNA sequences that we do not already know?

Acquiring nuclear DNA sequences in forest tree species is becoming easier as molecular tools are developing rapidly and we now have at our disposal an array of theoretical methods to carry out statistical inferences from multilocus sequence variation.In the present article we use results from two recent studies of nuclear DNA sequence polymorphism in Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) to illustrate what additional insights to each species' history can be gained compared with classical phylogeographic studies based on chloroplast or mitochondrial DNA.The sampling schemes and statistical analyses used in these two studies were similar facilitating a comparison between them.In both cases we inferred the presence of a rather severe bottleneck predating the Last Glacial Maximum (18,000 years ago).This result is discussed in relation to recent reassessments of the fossil pollen record and to its implication for our understanding of adaptation.Finally we briefly outline some suggestions for future research.