Postglacial range expansion and its genetic imprints in Abies alba (Mill.) — A synthesis from palaeobotanic and genetic data

We present a range-wide synthesis of our own research and related work on the complex postglacial history of Abies alba Mill. It is based on macroremains, fossil pollen records as well as on different genetic markers. The geographic distribution of genetic lineages and allele frequencies together with the fossil records confirm multiple refugia with at least three of them being sources for the Holocene range expansion into Central Europe, representing so-called effective refugia. One is located in the northern Apennines. A long-term refugium in the southern Balkans contributes to northward expansion with a branch along the Carpathians in the East and the Dinaric Alps in the West. Furthermore, new allozyme data indicate a third effective refugium in the northern or western Balkans, respectively. Using different genetic marker categories the differentiation of A. alba populations could be attributed to different time scales. A separation of maternal lineages took place in previous glacial cycles of the Quaternary, while a second pattern of genetic differentiation is the result of isolation processes during the last glaciation and subsequent gene flow after range expansion. Suture and introgression zones of refugial gene pools were clearly recognised. The patterns of genetic variation and genetic diversity spanning between rear and leading edges of the present range are discussed for evolutionary implications and conservation strategies.