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Eukaryotes are a holophyletic group of polyphyletic origin

Because of the polyphyletic origin of the eukaryotic monophylum, eukaryogenesis within prokaryotes is not comparable with mammal origin within paraphyletic reptiles. Both synapomorphies and plesiomorphies represent apomorphies and are indeed suitable for defining monophyletic (holophyletic and paraphyletic) groups. Alphaproteobacteria (Bacteria) and Asgard (Archaea) are the ancestors of LECA (the Last Eukaryotic Common Ancestor). The presence of ESPs in Asgard does not dispute the polyphyletic origin of eukaryotes ; it only further corroborates it. “Candidatus Prometheoarchaeum syntrophicum” is the closest relative to eukaryotes and the only Asgard with available microscopy data. This newly discovered species has a prokaryotic cell organization and does not exhibit features of eukaryotic complexity (nucleus, mitochondrion, meiotic cycle), and thus, it does not belong to Eukaryomorpha. Along with Cyanobacteria, non- photosynthetic eukaryotes are the ancestors of the primary photosynthetic eukaryotes (archaeplastidians). Non-photosynthetic eukaryotes are not the ancestors of plastids, hence LECA is not the only ancestor of the extant eukaryotic diversity. Eukaryotes are monophyletic by definition, as they have a single ancestor, LECA. They are also holophyletic as all LECA’s descendants belong to the same group. They are polyphyletic as well since they exhibit numerous symbioses and anastomoses in the tree of life. Symbiogenesis will always be one of the major forces driving eukaryotic evolution. A group of polyphyletic origin, such as eukaryotes, should not be assigned to a higher taxon that contains its single parent, as is the case with Eukaryomorpha.

Eukaryomorpha, archaea, alphaproteobacteria, eukaryogenesis, lichens, hybridization, symbiogenesis, paraphyly

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