The genetic basis for describing viruses as species.
The basis for the taxonomic definition of viruses or other species eventually has to be genetic. Since the beginning of the taxonomical considerations of organisms, the criterion that individuals can be grouped together on the basis of genetic compatibilities has been adopted as the guiding principle for describing a species. Although the genetic tests for grouping and distinguishing viruses may be different, the principle behind the species concept can still be applied. Also, the very existence of virus heredity and invokes the concept of speciation.