Long branch attraction (LBA) is a phenomenon in phylogenetic analyses (most commonly those employing maximum parsimony) when rapidly evolving lineages are inferred to be closely related, regardless of their true evolutionary relationships. For example, in DNA sequence-based analyses, the problem arises when sequences from two (or more) lineages evolve rapidly. There are only four possible nucleotides and when DNA substitution rates are high, the probability that two lineages will evolve the same nucleotide at the same site increases. When this happens, parsimony erroneously interprets this homoplasy as a synapomorphy (i.e., evolving once in the common ancestor of the two lineages).
This problem can be minimized by using methods that correct for multiple substitutions at the same site, by breaking up long branches, adding taxa related to those with the long branches or by using alternative slower evolving traits.
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