INTRODUCTION

In recent years, DNA sequences have become one of the most widely used sources for constructing phylogenetic trees. How can we test the accuracy of these construction efforts, considering that evolutionary events occurred in the past, mostly without human witnesses? Phylogenetic trees represent hypotheses of evolutionary relationships that can be explicitly tested using data. The example described in this animation does just that.

A group of investigators set up an experiment to track the evolution of a bacterial virus, called bacteriophage T7, in the laboratory. With the history of the T7 lineages known, the investigators could determine if a phylogenetic construction (based on the DNA sequences of the viruses at the endpoints of the lineages) matched the known history of the lineages.

CONCLUSION

In an experiment to test the accuracy of phylogenetic reconstruction methods, investigators followed the evolution of a bacterial virus as it reproduced over more than 1000 generations. The growth medium during these generations included a mutagen, which caused more nucleotide changes per replication cycle than normal, essentially speeding up evolutionary change. From this experiment, the investigators produced a known phylogenetic tree of 9 lineages. DNA sequences from the viruses at the endpoints of the lineages were given to another set of investigators, who used the sequence to reproduce an accurate phylogenetic tree of the viral lineages. Thus, this experiment provided a known phylogenetic tree that allowed the investigators to declare that their phylogenetic reconstruction was indeed accurate.

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Textbook Reference: Concept 16.2 Phylogeny Can Be Reconstructed from Traits of Organisms