Patterns of variation at a mitochondrial sequence-tagged-site locus provides new insights into the postglacial history of European Pinus sylvestris populations

Due to their maternal mode of inheritance, mitochondrial markers can be reg arded as almost 'ideal' tools in evolutionary studies of conifer population s. In the present study, polymorphism was analysed at one mitochondrial int ron (nad 1, exon B/C) in 23 native European Pinus sylvestris populations. I n a preliminary screening for variation using a polymerase chain reaction-r estriction fragment length polymorphism approach, two length variants were identified. By fully sequencing the 2.5 kb region, the observed length poly morphism was found to result from the insertion of a 31 bp sequence, with n o other mutations observed within the intron. A set of primers was designed flanking the observed mutation, which identified a novel sequence-tagged-s ite mitochondrial marker for P. sylvestris. Analysis of 747 trees from the 23 populations using these primers revealed the occurrence of two distinct haplotypes in Europe. Within the Iberian Peninsula, the two haplotypes exhi bited extensive population differentiation (Phi(ST) = 0.59; P less than or equal to 0.001) and a marked geographical structuring. In the populations o f central and northern Europe, one haplotype largely predominated, with the second being found in only one individual of one population.