Theoretical approaches to disclosing the emergence and adaptive advantages of multipartite viruses

•Around 16% of all viral species, mostly infecting plants, are multipartite.•Theoretical works assume a benefit of segmentation to compensate for the cost of complementation.•Successful complementation is compromised in plant virus due to frequent bottlenecks.•No general advantage of multipartitism has been experimentally identified yet.•The ecological perspective seems essential to clarify the emergence of multipartitism.