Mergeay Joachim, Vanoverbeke Joost, Verschuren Dirk, De Meester Luc
Laboratory of Aquatic Ecology, P.O. Box 02439, Katholieke Universiteit Leuven, Charles Deberiotstraat 32, 3000 Leuven, Belgium.
Ecology. 2007 Dec;88(12):3032-43. doi: 10.1890/06-1538.1.
Dormant propagule banks are important reservoirs of biological and genetic diversity of local communities and populations and provide buffering mechanisms against extinction. Although dormant stages of various plant and animal species are known to remain viable for decades and even centuries, little is known about the effective influence of recolonization from such old sources on the genetic continuity of intermittent populations under natural conditions. Using recent and old dormant eggs recovered from a dated lake sediment core in Kenya, we traced the genetic composition of a local population of the planktonic crustacean Daphnia barbata through a sequence of extinction and recolonization events. This was combined with a phylogeographic and population-genetic survey of regional populations. Four successive populations, fully separated in time, inhabited Lake Naivasha from ca. 1330 to 1570 AD, from ca. 1610 to 1720 AD, from ca. 1840 to 1940 AD, and from 1995 to the present (2001 AD). Our results strongly indicate genetic continuity between the 1840-1940 and 1995-2001 populations, which are separated in time by at least 50 years, and close genetic relatedness of them both to the 1330-1580 population. A software tool (Colonize) was developed to find the most likely source population of the refounded 1995-2001 population and to test the number of colonists involved in the recolonization event. The results confirmed that the 1995-2001 population most probably developed out of a limited number of surviving local dormant eggs from the previous population, rather than out of individuals from regional (central and southern Kenya) or more distant (Ethiopia, Zimbabwe) populations that may have immigrated to Lake Naivasha through passive dispersal. These results emphasize the importance of prolonged dormancy for the natural long-term dynamics of crustacean zooplankton in fluctuating environments and suggest an important role of old local dormant egg banks in aquatic habitat restoration.
休眠繁殖体库是当地群落和种群生物及遗传多样性的重要储存库，并提供了防止灭绝的缓冲机制。尽管已知各种动植物物种的休眠阶段能存活数十年甚至数百年，但对于在自然条件下，来自这些古老来源的重新定殖对间歇性种群遗传连续性的实际影响却知之甚少。利用从肯尼亚一个有年代记录的湖泊沉积物岩芯中获取的近期和古老休眠卵，我们通过一系列灭绝和重新定殖事件，追踪了浮游甲壳动物巴氏水蚤当地种群的遗传组成。这与对区域种群的系统地理学和种群遗传学调查相结合。四个在时间上完全分开的连续种群，大约在公元1330年至1570年、公元1610年至1720年、公元1840年至1940年以及从1995年到现在（公元2001年）居住在奈瓦沙湖。我们的结果有力地表明，在时间上相隔至少50年的1840 - 1940年和1995 - 2001年种群之间存在遗传连续性，并且它们两者与1330 - 1580年种群有密切的遗传关系。开发了一个软件工具（Colonize）来找出重新建立的1995 - 2001年种群最可能的源种群，并测试参与重新定殖事件的殖民者数量。结果证实，1995 - 2001年种群很可能是由前一个种群中有限数量存活的当地休眠卵发育而来，而不是由可能通过被动扩散迁移到奈瓦沙湖的区域（肯尼亚中部和南部）或更遥远（埃塞俄比亚、津巴布韦）种群的个体发育而来。这些结果强调了长时间休眠对于波动环境中甲壳动物浮游生物自然长期动态的重要性，并表明古老的当地休眠卵库在水生栖息地恢复中具有重要作用。
