  Consensus methods are widely used for combining phylogenetic trees into a
single estimate of the evolutionary tree for a group of species. As more taxa
are added, the new source trees may begin to tell a different evolutionary
story when restricted to the original set of taxa. However, if the new trees,
restricted to the original set of taxa, were to agree exactly with the earlier
trees, then we might hope that their consensus would either agree with or
resolve the original consensus tree. In this paper, we ask under what
conditions consensus methods exist that are 'future proof' in this sense. While
we show that some methods (e.g. Adams consensus) have this property for
specific types of input, we also establish a rather surprising `no-go' theorem:
there is no 'reasonable' consensus method that satisfies the future-proofing
property in general. We then investigate a second notion of 'future proofing'
for consensus methods, in which trees (rather than taxa) are added, and
establish some positive and negative results. We end with some questions for
future work.
