All four analyzed traits were coded as binary traits (presence “1” or absence “0”). While the sexual reproduction may be either present or absence, the mitotic traits have to be seen a little different. An absence for the closed nuclear division means that the nuclear envelope is open or semi-open during mitosis. For the intranuclear spindles, an absence corresponds to extranuclear spindles and the absence of orthomitosis (axial symmetry) stands for pleuromitosis (bilateral symmetry). The annotation of traits is based on literature (supplementary table S1, Supplementary Material online). Not every species in our data set is annotated for every trait in literature. We therefore applied a majority rule for each group in question. If there is data on the exact ancestral state of a trait, we annotated it to be present in the whole group. In cases where only one representative of a group is annotated in literature, this annotation was suspected to be present in the whole group. Groups with different annotations for different members were annotated by majority rule. No cases with a 50:50 distribution were found in our data set. Two species in our data set are annotated with incompatible mitotic combinations (closed orthomitosis with extranuclear spindle): Chlamydomonas reinhardtii and Volvox carteri, both members of the taxon Chlorophyceae. Although the combination of traits itself is incompatible, the majority rule resulted in this combination for the group.