Acknowledgements
We thank the curators of GB, LD, S, UME and UPS for providing the material used in this study. We are also grateful to Karin Wiklund, Peter Carlsson, Staffan Nilsson, and especially Tomas Hallingbäck, for their assistance during the fieldwork. The suggestions provided by Neil Bell and two anonymous referees have greatly improved the text, and we are deeply grateful to them for their advice.