A species concept states what should make organisms members of the same species; an operational criterion states what observations will test that claim. Reproductive isolation, distinguishable morphology and ancestry inferred through phylogenetics answer different questions. In a lineage-based interpretation, they are evidence for separation of evolving biological populations, and need not appear together. [ref]
Species Concepts and Species Delimitation by Kevin de Queiroz. pp. 880–883, Table 1, Figure 1 and “Conceptualization versus Delimitation”: distinguish defining properties from operational evidence
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