Homotopy decomposition of a group of symplectomorphisms of S2×S2

Abstract We continue the analysis started by Abreu, McDuff and Anjos of the topology of the group of symplectomorphisms of S 2 × S 2 when the ratio of the area of the two spheres lies in the interval (1,2]. We express the group, up to homotopy, as the pushout (or amalgam) of certain of its compact Lie subgroups. We use this to compute the homotopy type of the classifying space of the group of symplectomorphisms and the corresponding ring of characteristic classes for symplectic fibrations.