Missing links connect the phylogeographic structure of endangered red pandas, remaining as one species -- Ailurus fulgens, and expediting conservation

Monitoring biodiversity depends on well-informed taxonomy, reflecting the underlying biology of organisms critical for appropriate conservation management. The taxonomy of red pandas, endangered mammals distributed along a ~2500km montane range fringing the southern Tibetan Plateau, has been perplexing. Finally resolved as evolutionarily unique Musteloidea, further division of Ailurus into two geographic variants remains contentious. Red pandas are threatened by extinction from anthropogenic disturbances with consequent population decline; continued gene flow is therefore crucial to maintain adaptive potential. A recent phylogenomic study from sampling range ends and a constrictive species concept split red pandas into two species. Subsequent studies supplied additional data missing from their midrange. We evaluated GenBank mtDNA sequences from 393 animals, plotted sampling locations, and analyzed with and without midrange samples. Two sublineages of monophyletic Ailurus were weakly supported by one method when the midrange was excluded, but not when it was included. Using more stringent analyses, Ailurus was strongly confirmed as a single species in all circumstances, although the western sublineage (A. f. fulgens) was weakly supported within. Four haplogroups associated with specific regions, suggesting broad phylogeographic patterning and gene flow, with sympatric crossover and a cline bracketing unsampled Bhutan in the midrange. Red pandas are due for IUCN Red List reassessment in 2025; unwarranted taxonomic revision would delay and imperil action needed to prevent extinction. We recommend maintaining Ailurus as one species, recognizing and protecting biodiversity at one intraspecific level, allowing for gene flow in conservation management, and extensively investigating intergradation of midrange red pandas.