Post-glacial colonization of Western Europe brown bears from a cryptic Atlantic refugium out of the Iberian Peninsula

Abstract

The European brown bear (Ursus arctos) shows a particular phylogeography that has been used to illustrate the model for contraction-expansion dynamics related to glacial refugia in Southern European peninsulas. Recent studies, however, have nuanced the once generally accepted paradigm, indicating the existence of cryptic refugia for some species further north. In this paper we collected available data on chronology and mitochondrial haplotypes from Western European brown bears, adding new sequences from present day individuals from the Cantabrian (North Iberia) area, in order to reconstruct the dynamics of the species in the region. Both genetics and chronology show that the Iberian Pleistocene lineages were not the direct ancestors of the Holocene ones, the latter entering the Peninsula belatedly (around 10,000 years BP) with respect to other areas such as the British Isles. We therefore propose the existence of a cryptic refugium in continental Atlantic Europe, from where the bears would expand as the ice receded. The delay in the recolonization of the Iberian Peninsula could be due to the orographic characteristics of the Pyrenean-Cantabrian region and to the abundant presence of humans in the natural entrance to the Peninsula.

Keywords:

• Ursus arctos
• brown bear
• LGM
• postglacial colonization
• Iberian Peninsula
• criptic refugium

Acknowledgements

The authors are grateful to R. Hartasánchez and D. Pando of the Fund for the Protection of Wild Animals (FAPAS) for the donation of current Cantabrian brown bear hair samples, and J. Quesada of the Natural History Museum of Barcelona for the donation of samples of naturalised pelts for their genetic study. We thank Dr. Gloria González Fortes for their constant advice during this research and two anonymous reviewers for their valuable comments to a previous version of this paper, which greatly helped to improve the manuscript.