1. The sei whale (Balaenoptera borealis) presents a disjointed geographic distribution. Significant genetic divergence between sei whales from the North Atlantic (NA) and North Pacific (NP) have been recorded; however, limited samples from the Southern Hemisphere (SH) have precluded a global analysis.
2. The largest recorded mass mortality event occurred in Golfo de Penas, southern Chile, providing a primary source of SH samples. A global mitochondrial DNA phylogeographic study was undertaken including 111 SH samples (98 from Golfo de Penas), and new sequences from the NP.
3. A marked phylogeographic structure was observed between the three ocean basins' populations, with the highest Φ_ST values between NA–NP and NA–SH, and a lower but still significant value between SH–NP. This structure, and the haplotype distribution pattern, suggest a more recent separation between SH–NP and an absence of recurrent gene flow among all three populations. Only one potential migratory event was detected from SH to NA.
4. These results support an ongoing phylogeographic differentiation between all populations, highlighting the identity of each and the importance of independent management. Therefore, each population should represent a separate management unit, which is important in the development of conservation strategies.
5. Demographic analyses detected a recent reduction of population size in the SH and NA, but not in the NP. For all populations, estimated effective population sizes were higher than estimated census sizes. This suggests that most of the genetic diversity of pre-whaling populations is still retained; however, continued reduction in population sizes could lead to future loss of genetic diversity.
6. This study highlights the necessity of local protection and systematic monitoring of the Golfo de Penas sei whale population. In such a remote area the use of remote sensing techniques could be a cost-effective option for evaluating the threat, periodicity and magnitude of mortalities and their effect on the local whale population. The integration of genetic and demographic approaches improves the understanding of the dynamics of populations, which is particularly useful in endangered species.

中文翻译：

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濒临灭绝的塞鲸的系统地理学和人口统计推断，对保护的影响

1. 塞鲸（Balaenoptera borealis）呈现出不连贯的地理分布。来自北大西洋 (NA) 和北太平洋 (NP) 的塞鲸之间的显着遗传差异已被记录；然而，来自南半球 (SH) 的有限样本排除了全球分析。
2. 记录的最大的大规模死亡事件发生在智利南部的 Golfo de Penas，提供了 SH 样本的主要来源。进行了一项全球线粒体 DNA 系统地理学研究，包括 111 个 SH 样本（98 个来自 Golfo de Penas）和来自 NP 的新序列。
3. 在三个海洋盆地的种群之间观察到明显的系统地理学结构，NA-NP 和 NA-SH 之间的Φ _ST值最高，SH-NP 之间的值较低但仍然显着。这种结构和单倍型分布模式表明 SH-NP 之间最近的分离和所有三个种群之间没有重复的基因流动。仅检测到一次从 SH 到 NA 的潜在迁移事件。
4. 这些结果支持所有种群之间正在进行的系统地理学差异，突出了每个种群的身份和独立管理的重要性。因此，每个种群都应代表一个单独的管理单位，这对制定保护策略很重要。
5. 人口统计分析检测到最近 SH 和 NA 的人口规模减少，但 NP 没有。对于所有人口，估计的有效人口规模高于估计的人口普查规模。这表明捕鲸前种群的大部分遗传多样性仍然保留；然而，种群规模的持续减少可能导致未来遗传多样性的丧失。
6. 这项研究强调了对 Golfo de Penas sei 鲸鱼种群进行本地保护和系统监测的必要性。在这样一个偏远地区，使用遥感技术可能是评估死亡威胁、周期性和严重程度及其对当地鲸鱼种群影响的一种具有成本效益的选择。遗传和人口统计方法的整合提高了对种群动态的理解，这对濒危物种特别有用。