Taxonomic species recognition should be consistent.

Yet a proposed revision of Felidae taxonomy ignored the molecular data and lumped all five mainland tiger subspecies into one subspecies, distinct from the Sumatran tiger subspecies [[20]]. The biological species concept (BSC), which became the default species definition over 30 different species concepts, defines species as 'groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups' [[7]]. A subspecies has four possible fates: (i) extinction; (ii) connecting and interbreeding with another subspecies to become a new mixed subspecies; (iii) evolution into a new species; and (iv) staying the same [[17]]. [Extracted from the article]