Subspecies Taxonomy and Inter-Population Divergences of the Critically Endangered Yellow-Breasted Bunting: Evidence from Song Variations

SIMPLE SUMMARY: Identifying the taxonomic status of subspecies or population with independent evolutionary tendencies is important for the targeted conservation of endangered species. Two subspecies of the critically endangered, Yellow-breasted Bunting Emberiza aureola have long been classified: E. a. aureola and E. a. ornata. However, populations distributed in Hokkaido, Japan, are sometimes considered another subspecies of E. a. insulana. By comparing vocal divergences, we found that the song of the Yellow-breasted Bunting Emberiza aureola has subspecies-specific properties and that insulana can be classified acoustically as a subspecies. Morphological and genetic differences should be tested further to confirm its subspecies status. Our results not only confirm the subspecies but also provide key evidence for targeted taxon conservation efforts for this critically endangered bird species, given that several Japanese populations have disappeared. ABSTRACT: The critically endangered Yellow-breasted Bunting has undergone population collapse globally because of illegal hunting and habitat deterioration. It was listed as critically endangered (CR) by the International Union for Conservation of Nature (IUCN) in 2017 and designated a Class I (highest level) national conservation bird species in China in 2021. Birdsong in the breeding season is the main communicative signal under sexual selection, and song variations have long been considered critical evidence of divergence among subspecies or populations. We compared the songs of 89 males from 18 populations to test subspecies taxonomy. We found that songs of the Yellow-breasted Bunting Emberiza aureola are subspecies specific and that three subspecies can be clearly discriminated by song divergences. Moreover, an analysis of multiple vocal traits supports the claim that insulana is distinct from aureola and ornata. Finally, at the geographic population level, populations can be clearly classified in accordance with the three subspecies, although the aureola population in Xinjiang, China is differentiated from other populations of the same subspecies. The results of this study demonstrate that all populations and subspecies are unique and should be protected to maintain intraspecies song diversity. In addition, several specific populations, such as insulana populations in Japan and the Xinjiang, China population of aureola, need to be paid special attention to prevent the extinction of unique or local taxa.