[1] Norwegian Univ Life Sci, Dept Ecol & Nat Resource Management, NO-1432 As, Norway
[2] Norwegian Inst Nat Res, NO-7485 Trondheim, Norway
[3] Univ Tromso, Dept Biol, NO-9037 Tromso, Norway
[4] Univ Oslo, Dept Biol, CEES, NO-0316 Oslo, Norway
[5] CEFE, UMR 5175, F-34293 Montpellier 5, France