Data from: Blue whale population structure along the eastern South Pacific Ocean: Evidence of more than one population

Blue whale (Balaenoptera musculus) populations were among the most intensively exploited species of whales in the world. As a consequence of this intensive exploitation, blue whale sightings off the coast of Chile were uncommon by the end of the 20th century. In 2004 a feeding and nursing ground was reported in southern Chile. With the aim to investigate the genetic identity and relationship of these Chilean blue whales to those in other Southern Hemisphere areas, 60 biopsy samples were collected between 2003 to 2009 years. Samples were genotyped at seven microsatellite loci, and the mitochondrial control region was sequenced, allowing us to identify 52 individuals. To investigate the genetic identity of this suspected remnant population, we compared these 52 individuals to blue whales from Antarctica (ANT, n=96), Northern Chile (NCh, n=19) and the eastern tropical Pacific (ETP, n=31). No significant differentiation in haplotype frequencies (mtDNA) nor among genotypes (nDNA) were found between SCh, NCh and ETP, while significant differences were found between these three areas and Antarctica. When Bayesian clustering analyses were carried out, two distinct groups arose: i) ANT and ii) SCh, NCh and ETP. Our results suggest at least two isolated breeding population units or subspecies. This difference is also supported from other lines of evidence such as morphometrics and acoustics. The lack of differences detected between SCh/NCh/ETP areas supports the hypothesis that eastern South Pacific blue whales are using the ETP area as possible breeding area. Considering the small population sizes previously reported for the SCh area, additional conservation measures and monitoring of this population should be developed and prioritized.

蓝鲸（Balaenoptera musculus）是全球受捕捞强度最高的鲸类物种之一。受高强度捕捞影响，至20世纪末，智利沿海的蓝鲸目击记录已极为罕见。2004年，科研人员在智利南部海域发现一处蓝鲸觅食与育婴场。为探究智利蓝鲸的遗传特征及其与南半球其他海域蓝鲸的亲缘关系，研究团队于2003年至2009年间采集了60份组织活检样本。研究人员对7个微卫星位点（microsatellite loci）进行基因分型，并对线粒体控制区（mitochondrial control region）进行测序，最终鉴定出52个独特个体。为验证这一疑似残存种群的遗传特征，研究团队将这52个个体与南极海域（ANT，n=96）、智利北部（NCh，n=19）及东热带太平洋（ETP，n=31）的蓝鲸样本进行比对分析。结果显示，智利南部海域（SCh）、智利北部海域与东热带太平洋海域之间，无论是线粒体DNA（mtDNA）单倍型频率还是核DNA（nDNA）基因型，均未检测到显著遗传分化；而上述三个海域的种群与南极海域蓝鲸种群则存在显著遗传差异。贝叶斯聚类分析进一步揭示了两个独立的类群：其一为南极海域种群，其二为智利南部、智利北部及东热带太平洋海域种群。本研究结果表明，蓝鲸至少存在两个彼此隔离的繁殖种群单元或亚种。该结论亦得到形态测量学（morphometrics）与声学研究等多方面证据的支持。智利南部、智利北部与东热带太平洋海域种群间未检测到遗传差异，这一结果支持“东太平洋南部蓝鲸将东热带太平洋海域作为潜在繁殖场”的假说。鉴于此前报道的智利南部海域蓝鲸种群规模极小，该种群的额外保护措施与监测工作应尽快制定并予以优先推进。