Holocene distribution of woody taxa at the westernmost limit of the Circumboreal/Mediterranean boundary: Evidence from wood remains

Macrofossils and megafossils of different genera, which were found in twelve localities in the mountains of northwest Iberia, provide spatially precise evidence of their distribution in the region during the Holocene. Macrofossils were recovered from mires, eroded peat bogs and lakes, identified by their wood anatomy and dated using radiocarbon methods. Conifers (Pinus), deciduous trees (Betula, Salix, Quercus) and shrubs (Erica, Fabaceae) were identified. The findings of Pinus gr. sylvestris/nigra have special biogeographical significance. The available palaeoecological data from the Cantabrian Range and nearby mountains (Ancares and Courel) indicate that pines have grown during the Holocene over the highlands of the western part of the Cantabrian Range area as a natural vegetation element. Nevertheless, Pinus sylvestris is the only pine species that is currently present in the Cantabrian Mountains, and its natural distribution area is now limited to a few enclaves. In this study, we provide a number of conclusive findings demonstrating that the past distribution of Pinus gr. sylvestris/nigra in this region suffered an important range contraction during the last two millennia. Historical data also support this idea, as they strongly suggest that this species survived well into the historical period.

► We present data based on macro- and megafossils at the Holocene from 12 sites located in the mountains of NW Iberia. ► Pinus gr. sylvestris occurred over the highlands of the western Cantabrian Range as a natural element of the vegetation. ► In the westernmost mountains, other taxa (Betula, Quercus) were dominant over the forest landscapes. ► Historical, pollen and macrofossil data evidence that pines survived well into the historical period. ► Pine populations may have suffered an important demise and local extinctions during the last millennia.