Origin of land plants revisited in the light of sequence contamination and missing data

Knowing the closest relatives of land plants is key to understanding the complex adaptations to terrestrial life. Unfortunately, multi-gene analyses yield highly incongruent results, suggesting for instance Charales, Zygnematales, or Coleochaete as the sister-group of land plants. Such controversy may result from the real history of life, in particular closely spaced speciation events, incomplete lineage sorting, gene duplication or horizontal gene transfer. In such cases, the solution resides in improved taxon sampling and sophisticated models of evolution. However, we will show that the quality of data used to infer the phylogeny may also play a major role, creating unnecessary controversy. In particular, the inclusion of contaminant sequences from other species, and of genes with incomplete taxon sampling explains a large part of the discrepancies observed between various studies. The use of a carefully checked and almost complete dataset suggests that land plants are closely related to a group composed of Zygnematales and Coleochaetales.