[1] Univ Vigo, Fac Biol, Dept Ecol & Biol Anim, Vigo 36310, Spain
[2] Lancaster Environm Ctr, UK Ctr Ecol & Hydrol, Lancaster, England
[3] Natl Environm Isotope Facil, Radiocarbon Lab, Glasgow, Lanark, Scotland
[4] Univ York, Dept Biol, York, N Yorkshire, England