We then define the mathematical problem of taxa-counting, which is equivalent to finding the chromatic number of a graph, a well-known NP-hard problem.
However, the problem of rogue taxa continues to also be a problem for supermatrices and therefore the development of solutions will likely benefit both methods.
Besides the potential problem of limited taxa and gene sampling, the tree topology may be more influenced by the final alignment itself than by the phylogenetic reconstruction method [ 54, 55].
Statistical correlation of traits between different species without incorporation of their evolutionary relationships suffers from the problem of phylogenetic nonindependence as taxa may be similar simply due to shared ancestry.
For the anthropologist, there is the additional problem of applying findings from extant taxa to extinct taxa with potentially different morphologies and limb proportions.
The availability of complete genomes and a robust phylogenetic history allow the identification of these taxonomical problems and the preliminary identification of taxa that might be regarded as good candidates for new species.
One problem of each type involved five taxa and the other involved six.
In the second-round phylogenetic analyses, to resolve the problem of long-branch attraction, 5 taxa (2 nematodes and 3 platyhelminths) showing extremely long branches (Fig. 5 and [additional file 4]) were excluded from the original data set used in the first step.
We point out that instead of the two biases mentioned by Barthélémy et al. [ 1], the problems encountered are incident to the limited set of taxa sampled.
In the maximum parsimony problem, there are known character-states for a set of taxa (of the species) or Operational Taxonomic Units (OTUs).
Darwin addresses the species question by raising the problems caused by natural variation in the practical discrimination of taxa at the species and varietal levels.
