Origin and diversification of eukaryotes.

The bulk of the diversity of eukaryotic life is microbial. Although the larger eukaryotes-namely plants, animals, and fungi-dominate our visual landscapes, microbial lineages compose the greater part of both genetic diversity and biomass, and contain many evolutionary innovations. Our understanding of the origin and diversification of eukaryotes has improved substantially with analyses of molecular data from diverse lineages. These data have provided insight into the nature of the genome of the last eukaryotic common ancestor (LECA). Yet, the origin of key eukaryotic features, namely the nucleus and cytoskeleton, remains poorly understood. In contrast, the past decades have seen considerable refinement in hypotheses on the major branching events in the evolution of eukaryotic diversity. New insights have also emerged, including evidence for the acquisition of mitochondria at the time of the origin of eukaryotes and data supporting the dynamic nature of genomes in LECA.