We maintain the minimum spanning tree of a point set in the plane subj
ect to point insertions and deletions, in amortized time O(n1/2 log2 n
) per update operation. We reduce the problem to maintaining bichromat
ic closest pairs, which we solve in time O(n(epsilon)) per update. Our
algorithm uses a novel construction, the ordered nearest neighbor pat
h of a set of points. Our results generalize to higher dimensions, and
to fully dynamic algorithms for maintaining minima of binary function
s, including the diameter of a point set and the bichromatic farthest
pair.