Virus evolution and taxonomy

Abstract

With the demonstration of the existence of viruses over 100 years ago, and the plethora of different viruses subsequently described in all types of cells, it became urgent to classify these microorganisms. The first efforts in this direction were initiated in 1966, and in 1973 the International Committee on Taxonomy of Viruses was created. The task of this committee is to classify viruses hierarchically, using the four main taxa, order, family, genus and species. However, classification is rendered difficult because major elements drive virus evolution, such as mutation, recombination and reassortment. Plant viruses are very well suited to establish a means of virus classification and to study virus evolution, given the ease with which large numbers of plants can be infected and high yields of virus rapidly obtained. In addition, using plant viruses obviates the restrictions generally linked to animal experimentation. Examples are provided among plant viruses illustrating the extent to which some of the elements driving evolution have participated in structuring the viruses known today, and hence the complexity there is in constructing phylogenetic trees of viruses. Consequently, grouping viruses in a durable taxonomic system is particularly hazardous and classification must proceed with caution. © 2008 Springer Berlin Heidelberg.