Current understanding of the postglacial colonization of Nearctic and Palearctic species relies heavily on inferences drawn from the phylogeographic analysis of contemporary generic variants. Modern postglacial populations are supposed to be representative of their Pleistocene ancestors, and their current distribution is assumed to reflect the different colonization success and dispersal patterns of refugial lineages. Yet, testing of phylogeographic models against ancestral genomes from glacial refugia has rarely been possible. Here we compare ND1 mitochondrial DNA variation in late Pleistocene (16,000-40,000 years before present), historical and contemporary Atlantic salmon (Salmo salar) populations from northern Spain and other regions of western Europe. Our study demonstrates the presence of Atlantic salmon in the Iberian glacial refugium during the last 40,000 years and points to the Iberian Peninsula as the likely source of the most common haplotype within the Atlantic lineage in Europe. However, our findings also suggest that there may have been significant changes in the genetic structure of the Iberian refugial stock since the last ice age, and question whether modern populations in refugial areas are representative of ice age populations. A common haplotype that persisted in the Iberian Peninsula during the Pleistocene last glacial maximum is now extremely rare or absent from European rivers, highlighting the need for caution when making phylogeographic inferences about the origin and distribution of modern genetic types.

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ABSTRACT. Excavations since 1996 in the large El Mirón Cave in the Cantabrian Cordillera of northern Spain have revealed a cultural sequence of late Mousterian, early Upper Paleolithic, Solutrean, Magdalenian, Azilian, Mesolithic, Neolithic, Chalcolithic, Bronze Age, and Medieval occupations. These components have been dated by 51 generally coherent radiocarbon determinations, all run by the Geochron labs, in association with the Lawrence Livermore labs for AMS. This series is one of the largest for a single prehistoric site in Iberia or even Europe. The series is consistent with the record from Cantabrian Spain and provides new detail on the age of the Middle-Upper Paleolithic transition, on the various phases of the Magdalenian culture, on the appearance of the Neolithic in the Atlantic zone of Spain, and on the origins of the socioeconomic complexity in the metal ages. The stratigraphic relationship of 14 C-dated levels to a roof-fall block and adjacent cave walls (both with engravings) provides rare terminus post and ante quem ages for execution of the rupestral art in El Mirón during the early to mid Magdalenian. The 14 C record has also been instrumental in revealing the existence of depositional hiati during the early Holocene.

During the last 10 years or so, magnetic susceptibility (MS) measurements of cave sediments from archaeological sites have been used for intrasite correlation and paleoclimate estimation. This is possible, if the context is appropriate, because the MS of these sediments result from climate processes active outside caves causing variations in magnetic properties of the sediments ultimately accumulating inside of caves. Once deposited, these materials are preserved, and their stratigraphy provides a climate proxy that can be extracted. Here, using the magnetosusceptibility event and cyclostratigraphy (MSEC) method and graphic correlation, we present a paleoclimatic framework for the last 40,000 years for southern Europe and demonstrate the intersite correlation power of the method. Our preliminary result for southern Europe represents climate fluctuations from ϳ43,000 to ϳ3,000 yr B.P. (we use here uncalibrated ages). The results correlate well with independent climate indicators, and because these data are robust, they can be used in relative dating. ᭧

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