Old versus new characters for systematics: Cautionary tales from virology

Abstract

Molecular sequence information about viruses has mostly confirmed the groupings devised by traditional taxonomic methods, but shown in addition that the genes of related species may differ in number, arrangement, orientation and in sequence homology. It has also revealed that true genetic recombination between viruses has been common, even among those with RNA genomes, indeed most virus groups seem to have arisen y recombination. Thus, there is an unexpected wealth of genetic chaos hidden behind the fatade of the phenotype, and it is possible that the difficulties that plant taxonomists have had in identifying the relationships of the major groupings of plants could have similar causes. Nonetheless, molecular taxonomy does give sensible results and this is illustrated by a classification of the large subunit Rubisco proteins of 21 plant species based on their amino acid sequences.