Multipartite viruses: adaptive trick or evolutionary treat?

Pie chart showing the abundances of all currently annotated species in the ICTV (2015) for each viral family.18 Figures around the pie indicate the number of species in a given family. Colors link to a viral family in the color legend. In the legend the number of genera corresponding to each family is given in parenthesis. Families with four or less species are merged together. Pop charts contain multipartite (solid line) and segmented (dashed line) viral families (name in bold face), and show the number of multipartite or segmented species/total number of species. Background colors of the pop charts indicate the main host. List of families with four or less viral species, with the number of genera first given between brackets if different from one: *ssDNA: Bacilladnavirus 1, Spiraviridae 1, Genomoviridae 1, Bidnaviridae 1; *ssRNA(+): Leviviridae (2) 4, Hypoviridae 4, Benyviridae 4, Ourmiavirus 3, Bacillarnavirus 3, Albetovirus 3, Sinaivirus 2, Jingmenvirus 2, Permutotetraviridae 2, Sarthroviridae 1, Carmotetraviridae 1, Barnaviridae 1, Alvernaviridae 1, Gammaflexiviridae 1, Marnaviridae 1, Roniviridae 1, Virtovirus 1, Polemovirus 1, Papanivirus 1, Labyrnavirus 1, Idaeovirus 1, Higrevirus 1, Cilevirus 1, Aumaivirus 1; *ssRNA(？): Nyamiviridae (2) 4, Deltavirus 1, Wastrivirus 1, Crustavirus 1, Chengtivirus 1, Arlivirus 1, Anphevirus 1, Sunviridae 1, Mymonaviridae 1; *dsRNA: Amalgaviridae 4, Picobirnaviridae 2, Botybirnavirus 1, Quadriviridae 1, Megabirnaviridae 1, Cystoviridae