Geography and Environment, University of Southampton, Southampton, S017 1BJ, UK;
Alaska Quaternary Center, university of Alaska, Fairbanks, AK 99775, USA;
Biology Department, Middlebury College, Vermont 05753, USA;
Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775-7000, USA;
School of Biological Sciences, University of Portsmouth, Portsmouth PO1 2DY, UK;