Accurate species delineation is critical for implementing evidence-based conservation frameworks for endangered species, enabling precise prioritisation of ecological interventions and allocation of conservation resources. Traditionally, finless porpoises across the Indo-Pacific waters were classified into a single species Neophocaena phocaenoides with subdivision of three subspecies. In the past two decades, the finless porpoise has been divided into two separate species: the Indo-Pacific finless porpoise N. phocaenoides and the narrow-ridged finless porpoise N. asiaeorientalis, with the Yangtze finless porpoise as the subspecies (N. a. asiaeorientalis) or freshwater population of the latter. In this review, we synthesise multidisciplinary evidence from morphological and anatomical measurements, biochemical and molecular genetic markers and comparative and population genomics to assess the taxonomic status of the Yangtze finless porpoise. Our synthesis reveals obvious differences between the Yangtze finless porpoise and those marine finless porpoises including (but not limited to) body colour, the length and height of dorsal ridge and the width of tubercule, various skull metrics and life history characteristics, genetic structure by multiple molecular markers. Most notably, recent population genomics studies have uncovered significant genetic structure and especially adaptive evolution associated with water homeostasis and urea cycle, providing the strongest molecular evidence to date for reproductive isolation. In combination with systematic differences in other aspects, we strongly suggest that the critically endangered Yangtze finless porpoise should be given an independent full species status (N. asiaeorientalis), reproductively isolated from its marine counterparts, the Indo-Pacific finless porpoise N. phocaenoides and the East Asian finless porpoise N. sunameri. Formal taxonomic recognition is critical for effective conservation, as it mobilises enhanced legal protections under national and international frameworks, secures dedicated conservation resources and affirms the irreplaceable evolutionary heritage value of this lineage, none of which would be automatically guaranteed under a subspecific classification.
DOI: 10.3897/natureconservation.64.193600
Publication Date: 2026-06-12