long branch attraction

Long branch attraction (LBA) is a problem in phylogenetic analyses, particularly in those analyses employing the non-parametric statistical method termed maximum parsimony.

In LBA, rapidly evolving lineages are inferred to be closely related, regardless of their true evolutionary relationships. This problem in analysis arises when the DNA of two (or more) lineages evolves rapidly. Because there are only four possible nucleotides, high rates of DNA substitution create the probability that two separate lineages will convergently evolve the same nucleotide at the same locus. In such cases, parsimony erroneously interprets this similarity as a synapomorphy, that is, as having evolved once in the common ancestor of the two lineages. The problem of LBA can be minimized by applying statistical methods that incorporate differential rates of substitution among lineages, such as maximum likelihood, or by breaking up long branches by adding taxa that are related to those with the long branches.