Figure 7.

Since the discovery of the first virus, tobacco mosaic virus, more than 100 years ago, the study of plant viruses has provided fundamental insights into numerous aspects of biology, including biochemistry, structural biology, genetics, and, as illustrated here, evolutionary biology. Shown here is a schematic diagram of the distribution of virus diversity in a single plant host, with different colors of branches and leaves illustrating the diversity of haplotypes isolated from different locations on a single, chronically infected host tree. The results demonstrate that several distinct subpopulations of Plum pox virus differentiate and evolve independently in different locations of a single tree. Closely related colors represent closely related haplotypes. (Photo provided by Michel Yvon, Chiraz Jridi, and Stéphane Blanc.) (This figure first appeared on the cover of the Journal of Virology, June 2006, vol. 80, no. 12. [See related article in March 2006, vol. 80, no. 5, p. 2349.])