RESUMEN
Norway spruce (Picea abies [L.] Karst.) is a broadly distributed European conifer tree whose history has been intensively studied by means of fossil records to infer the location of full-glacial refugia and the main routes of postglacial colonization. Here we use recently compiled fossil pollen data as a template to examine how past demographic events have influenced the species' modern genetic diversity. Variation was assessed in the mitochondrial nad1 gene containing two minisatellite regions. Among the 369 populations (4876 trees) assayed, 28 mitochondrial variants were identified. The patterns of population subdivision superimposed on interpolated fossil pollen distributions indicate that survival in separate refugia and postglacial colonization has led to significant structuring of genetic variation in the southern range of the species. The populations in the northern range, on the other hand, showed a shallow genetic structure consistent with the fossil pollen data, suggesting that the vast northern range was colonized from a single refugium. Although the genetic diversity decreased away from the putative refugia, there were large differences between different colonization routes. In the Alps, the diversity decreased over short distances, probably as a result of population bottlenecks caused by the presence of competing tree species. In northern Europe, the diversity was maintained across large areas, corroborating fossil pollen data in suggesting that colonization took place at high population densities. The genetic diversity increased north of the Carpathians, probably as a result of admixture of expanding populations from two separate refugia.
Asunto(s)
Fósiles , Genética de Población , Picea/genética , Polen/genética , ADN Mitocondrial/genética , ADN de Plantas/genética , Europa (Continente) , Evolución Molecular , Variación Genética , Geografía , Repeticiones de Minisatélite , Filogenia , Análisis de Componente Principal , Análisis de Secuencia de ADN , Árboles/genéticaRESUMEN
BACKGROUND: The reconstruction of biological processes and human activities during the last glacial cycle relies mainly on data from biological remains. Highly abundant tissues, such as wood, are candidates for a genetic analysis of past populations. While well-authenticated DNA has now been recovered from various fossil remains, the final 'proof' is still missing for wood, despite some promising studies. SCOPE: The goal of this study was to determine if ancient wood can be analysed routinely in studies of archaeology and palaeogenetics. An experiment was designed which included blind testing, independent replicates, extensive contamination controls and rigorous statistical tests. Ten samples of ancient wood from major European forest tree genera were analysed with plastid DNA markers. CONCLUSIONS: Authentic DNA was retrieved from wood samples up to 1,000 years of age. A new tool for real-time vegetation history and archaeology is ready to use.
