  We consider the problem of estimating the evolutionary history of a set of
species (phylogeny or species tree) from several genes. It is known that the
evolutionary history of individual genes (gene trees) might be topologically
distinct from each other and from the underlying species tree, possibly
confounding phylogenetic analysis. A further complication in practice is that
one has to estimate gene trees from molecular sequences of finite length. We
provide the first full data-requirement analysis of a species tree
reconstruction method that takes into account estimation errors at the gene
level. Under that criterion, we also devise a novel reconstruction algorithm
that provably improves over all previous methods in a regime of interest.
