ecological niche was adopted.

As of 2021 (the latest edition of the ICVCN), the ICTV definition of species states: "A species is the lowest taxonomic level in the hierarchy approved by the ICTV. A species is a monophyletic group of MGEs (mobile genetic elements) whose properties can be distinguished from those of other species by multiple criteria", with the comment "The criteria by which different species within a genus are distinguished shall be established