Genetic diversity and population demography of narrow‐ridged finless porpoises from South Korea on the basis of mitochondrial DNA variation: Implications for its conservation in East Asia

Abstract

The narrow‐ridged finless porpoise, Neophocaena asiaeorientalis, is a small cetacean inhabiting the coastal waters of Taiwan, East China, Korea, and Japan, and is threatened by anthropogenic pressures. We analyzed the mitochondrial control region of N. asiaeorientalis from Korean waters to better understand the genetic diversity, population structure, and demographic history through comparison with previously reported sequences from Japan and China. The network and phylogenetic analyses illustrated that few common haplotypes were centrally located, and that most of the unique haplotypes were on the edges of the branches. Moreover, the estimates of fixation indices and gene flow revealed significant genetic differentiation among the regions in East Asia. The mismatch distribution suggested a population expansion in the late Pleistocene. We propose that the current genetic variation in N. asiaeorientalis in East Asia was shaped by historical demographic expansion during the late Pleistocene. The N. asiaeorientalis of Korean waters has the highest diversity observed with the sampling available at this time. However, the abundance of N. asiaeorientalis in Korean waters has rapidly declined and the species needs protection from bycatch.

Adhesive Bowel Obstruction (ABO) in a Stranded Narrow-Ridged Finless Porpoise (Neophocaena asiaeorientalis sunameri)

“…Cetaceans serve as umbrella species at the top of the marine ecosystem [38,39], playing a crucial role as keystone species that define the entire environmental conditions [40], including various factors such as micro-plastics, contaminants, epidemics, and pollution [41,42]. However, the NRFP is currently listed as an endangered species on the International Union for Conservation of Nature (IUCN) Red List, reflecting a significant decline in its population in recent years [43]. To address this issue, it is imperative to establish a continuous monitoring system for the NRFP population and the emergence of diseases within the marine environment of Korean seawater.…”

Different Microsatellite Mutation Models May Lead to Contrasting Demographic Inferences through Genealogy-Based Approaches: A Case Study of the Finless Porpoise off the East Asian Coast

“…Meanwhile, the Yangtze River was connected to the East China Sea through the paleo-river mouths, strengthening the connection between the epicontinental areas of the northern East China Sea and southern Yellow Sea [48]. The finless porpoise found in the BS is exclusively the narrow-ridged form, and it differs genetically from the porpoises seen around the Yangtze River mouth (the mid-East China Sea) and off the Korean coast in the Yellow Sea [27]. from Bohai Sea and wide-ridged finless porpoise (N. phocaenoides) from South China Sea (Pearl River Delta region).…”

“…The Taiwan Strait (TWS): two currently recognized species, the narrow-ridged and the wide-ridged finless porpoise inhabit waters of TWS and they appear to have been reproductively isolated since the LGM [24]. Occasional sally of species were seen, e.g., Lee et al [27] reported two wide-ridged finless porpoises stranded on Jeju Island, Korea, while narrow-ridged finless porpoises have been found stranded, albeit very rarely, in Hong Kong [29]. Whether these distant migrations can lead to efficient gene flow remains unknown.…”

“…Genetic differentiation was also observed within the porpoise populations of each marine basin. For instance, Li et al [26] found a moderate differentiation between the narrow-ridged porpoise in the Bohai Sea and Yangtze River mouth, while Lee et al [27] reported a genetic differentiation between the narrow-ridged porpoises off the east-and west coast of Yellow Sea. Another recent study suggested that the wide-ridged finless porpoise from the Pearl River Delta (PRD) region and Taiwan Strait represent two genetic populations [28], and even deeper divergence was recently found between the porpoises in northern South China Sea and the Gulf of Thailand [29].…”

“…Therefore, we should expect a relatively fast rate of substitutions (calculated in generations) compared to other cetacean species. Moreover, evidence of genetic structure was commonly noted within the range of currently recognized species [26,27,29,30], and some of the "intra-species" divergence was considerably higher than the "inter-species" divergence [28,29,[36][37][38]. Instead of being an exceptional case [31], it was proposed that the interplay between glacial barrier, geographic isolation, and unknown vicariance may have shaped a multilevel divergence of the genus [28,36], which, however, remains to be tested with a more comprehensive sampling scheme [28].…”