Demographic collapse and low genetic diversity of the Irrawaddy dolphin population inhabiting the Mekong River

In threatened wildlife populations, it is important to determine whether observed low genetic diversity may be due to recent anthropogenic pressure or the consequence of historic events. Historical size of the Irrawaddy dolphin (Orcaella brevirostris) population inhabiting the Mekong River is unknown and there is significant concern for long-term survival of the remaining population as a result of low abundance, slow reproduction rate, high neonatal mortality, and continuing anthropogenic threats. We investigated population structure and reconstructed the demographic history based on 60 Irrawaddy dolphins samples collected between 2001 and 2009. The phylogenetic analysis indicated reciprocal monophyly of Mekong River Orcaella haplotypes with respect to haplotypes from other populations, suggesting long-standing isolation of the Mekong dolphin population from other Orcaella populations. We found that at least 85% of all individuals in the two main study areas: Kratie and Stung Treng, bor...

在受胁野生动物种群中，明确观测到的低遗传多样性究竟源于近期人为活动压力，还是历史事件的遗留影响，是一项至关重要的研究课题。栖息于湄公河的伊洛瓦底江豚（Irrawaddy dolphin, Orcaella brevirostris）的历史种群规模至今未知；该种群现存个体数量稀少、繁殖速率缓慢、新生幼崽死亡率偏高，且持续面临人为活动威胁，因此其长期生存前景引发了广泛担忧。本研究基于2001年至2009年间采集的60份伊洛瓦底江豚样本，对其种群结构展开了调查，并重构了该种群的人口统计学历史。系统发育分析结果显示，湄公河种群的伊洛瓦底江豚单倍型与其他种群的单倍型呈互单系关系，这表明湄公河江豚种群与其他伊洛瓦底江豚种群之间存在长期的生殖隔离。本研究发现，在两个主要研究区域——桔井省（Kratie）与上丁省（Stung Treng）中，至少85%的个体bor...