Collaborative Research: Abandoned Elephant Seal Colonies in Antarctica: Integration of Genetic, Isotopic, and Geologic Approaches toward Understanding Holocene Environmental Change

在之前由美国国家科学基金会赞助的研究中，PI发现南象海豹曾经存在于南极洲维多利亚陆地海岸（VLC），这一地区不再被观察到。海豹皮和毛的蜕皮发生在300公里的海岸线上，距离任何现存的栖息地都超过1000公里。在前殖民地的最后一次海豹记录是在公元~年1600. 由于遗弃发生在亚南极封海豹之前，VLC群落的消失可能是由于环境因素，可能是冷却和陆地固定的侵蚀，常年海冰使得进入拖出地点变得困难。因此，沿VLC的海豹栖息记录有可能作为气候变化的代表。象海豹主要是亚南极物种，分布在极地周围。遗传研究揭示了种群之间的显著分化，特别是在麦格理I.，这是最接近被遗弃的VLC殖民地的现存种群。麦格理种群不仅在遗传上是独特的，而且在过去的50年里，它经历了每年2%的无法解释的下降。在一项初步研究中，遗传分析显示了VLC海豹和麦格理岛海豹之间的密切关系。了解两个种群之间的关系，以及导致VLC种群消亡的环境压力，将有助于更好地了解当今种群的遗传结构，环境变化对海豹种群的影响，以及可能导致麦格理岛海豹数量下降的原因。该项目解决了几个关键的研究问题：(1)为什么象海豹殖民然后放弃了VLC？(2)海象记录揭示了全新世气候变化和海冰状况的哪些信息？(3)海豹的觅食策略是什么？这些策略是否随着气候的变化而变化？(4) VLC海豹的遗传结构与现存种群的关系如何？(5)遗传多样性如何随时间和种群数量的减少而变化？(6)利用古代样本估计mtDNA突变率，可以了解VLC种群随时间的动态变化？(7)象海豹和阿德利企鹅在同一地点，但显然在不同的时间，它们之间的生态关系是什么？拟议的工作包括对年轻研究人员进行专业培训，并将数据纳入研究生和本科生课程。

During previous NSF-sponsored research, the PI's discovered that southern elephant seal colonies once existed along the Victoria Land coast (VLC) of Antarctica, a region where they are no longer observed. Molted seal skin and hair occur along 300 km of coastline, more than 1000 km from any extant colony. The last record of a seal at a former colony site is at ~A.D. 1600. Because abandonment occurred prior to subantarctic sealing, disappearance of the VLC colony probably was due to environmental factors, possibly cooling and encroachment of land-fast, perennial sea ice that made access to haul-out sites difficult. The record of seal inhabitation along the VLC, therefore, has potential as a proxy for climate change. Elephant seals are a predominantly subantarctic species with circumpolar distribution. Genetic studies have revealed significant differentiation among populations, particularly with regard to that at Macquarie I., which is the extant population nearest to the abandoned VLC colony. Not only is the Macquarie population unique genetically, but it is has undergone unexplained decline of 2%/yr over the last 50 years3. In a pilot study, genetic analyses showed a close relationship between the VLC seals and those at Macquarie I. An understanding of the relationship between the two populations, as well as of the environmental pressures that led to the demise of the VLC colonies, will provide a better understanding of present-day population genetic structure, the effect of environmental change on seal populations, and possibly the reasons underlying the modern decline at Macquarie Island.This project addresses several key research problems: (1) Why did elephant seals colonize and then abandon the VLC? (2) What does the elephant seal record reveal about Holocene climate change and sea-ice conditions? (3) What were the foraging strategies of the seals and did these strategies change over time as climate varied? (4) How does the genetic structure of the VLC seals relate to extant populations? (5) How did genetic diversity change over time and with colony decline? (6) Using ancient samples to estimate mtDNA mutation rates, what can be learned about VLC population dynamics over time? (7) What was the ecological relationship between elephant seals and Adelie penguins that occupied the same sites, but apparently at different times? The proposed work includes the professional training of young researchers and incorporation of data into graduate and undergraduate courses.