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Figure 1 | BMC Evolutionary Biology

Figure 1

From: A genomic timescale for the origin of eukaryotes

Figure 1

Working model of gene relationships used in this study. Eukaryotic proteins trace back to four different locations in the evolutionary tree of prokaryotes. The divergence between archaebacteria and eubacteria (last common ancestor, LCA), archaebacteria and eukaryotes (AK), and between cyanobacteria and other eubacteria (BC) are believed to represent speciation events between populations of prokaryotes. The remaining three divergence events are considered to reflect horizontal gene transfer following symbiosis: (1) between an archaebacterium and a eubacterium leading to the origin of eukaryotes (BK-o), (2) between an α-proteobacterium and a eukaryote leading to the origin of mitochondria (BK-m), and (3) between a cyanobacterium and a eukaryote leading to the origin of plastids (BK-p). In this study, divergence times are estimated for AK, BC, BK-o, and BK-m. The divergence time of a fifth event (not shown), the speciation event between a eukaryote (Giardia) and other eukaryotes (GK), also is estimated. Branch lengths are not proportional to time.

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