Open Mitosis: Nuclear Envelope Dynamics 211
not found in more basal lineages, open mitosis likely evolved independently
in the different kingdoms and is a result of convergent evolution of mitotic
mechanisms rather than divergence from a common ancestor (see Fig. 1).
When did open mitosis arise in the plant lineage? The evolutionary an-
cestors of the higher plants are the green algae. Modes of mitosis found in
green algae include the proposed archetype of eukaryotic mitosis via kary-
Fig. 1Occurrence of closed and open mitosis in eukaryotes after mitochondrial endosym-
biosis (phylogeny based on Hedges 2002).Asterisksmark independent appearances of
open mitosis during evolution. Theboxedphyla represent organisms with plastids origi-
nating from photosynthetic endosymbiosis (Moreira et al. 2000)
Fig. 2 Variations in mitotic features present in the groups of green algae implicated in
the ancestry of land plants. Presence or absence of features listed on top are marked by
plusandminus, respectively. TheboxindicatesCharophyta(Based on van den Hoek et al.
1995; McCourt et al. 2004)