Some advantages and limitations of mitosis as a phylogenetic criterion

The advantages and disadvantages of mitosis as a phylogenetic character are discussed. Mitosis is suggested to be a good character on the grounds that it is universally applicable and that it reflects features of the basic organism since it is unlikely to have arisen through multiple endosymbiotic events. Since mitosis is an absolutely essential feature of the cell cycle it is subject to a great deal of evolutionary pressure and one would not expect a priori that relatively inefficient mitotic apparatuses would persist. It is suggested that supposedly primitive mitotic apparatuses are not inefficient and that the evidence that they are functionally different from those of higher organisms is largely negative electron microscopic evidence. This type of evidence is not very satisfactory since it can result from poor preservation and consequently it should be continually retested. Another weakness of mitosis as a phylogenetic criterion (shared with other essentially morphological criteria) is that there is no easy way to relate structural change with genetic change. Thus, while mitosis is a useful phylogenetic character, its usefulness is limited.