Chloroplast microsatellites as a tool for phylogeographic studies: the case of white oaks in Poland

Assessing the distribution of chloroplast DNA (cpDNA) haplotype variation is useful for studying the phylogeography of angiosperms. In the last two decades the cpDNA phylogeography of white oaks in Europe has been extensively studied, mostly based on the PCR-RFLP technique. However, PCR-RFLPs have low mutation rates and are primarily useful for reconstructing patterns at large geographical scales and lack resolution at fine spatial scales. Here we evaluate the usefulness of chloroplast microsatellites (cpSSR) as an alternative to PCR-RFLPs in Polish oak populations which have been underrepresented in previous studies. Eighty-five cpSSR haplotypes were detected using 14 cpSSR loci and a broad collection of 6680 trees sampled throughout Poland. Haplotype diversity was significantly lower in Q. petraea (H-e = 0.798) than in Q. robur (H-e = 0.820). Only 17 haplotypes (H01-H17) were found in 13 or more individuals, comprising together 97.9% of the sample. Most frequent cpSSR haplotypes were related to PCR-RFLP haplotypes, establishing the cross-references between the two marker systems. There was significant concordance between the matrices of genetic distances obtained by PCR-RFLP haplotypes and cpSSR haplotypes. Phylogenetic relationships among cpSSR haplotypes supported the existence of the three predominant maternal lineages of oaks in Poland: Iberian (7.8%), Apennine (20.6%) and Balkan (65.5%). The results are discussed with regards to the usefulness of cpSSR markers for phylogeographic studies.