Ims R A, Andreassen H P
Department of Biology, University of Oslo, Norway.
Nature. 2000 Nov 9;408(6809):194-6. doi: 10.1038/35041562.
Northern vole populations exhibit large-scale, spatially synchronous population dynamics. Such cases of population synchrony provide excellent opportunities for distinguishing between local intrinsic and regional extrinsic mechanisms of population regulation. Analyses of large-scale survey data and theoretical modelling have indicated several plausible synchronizing mechanisms. It is difficult, however, to determine the most important one without detailed data on local demographic processes. Here we combine results from two field studies in southeastern Norway--one identifies local demographic mechanisms and landscape-level annual synchrony among 28 enclosed experimental populations and the other examines region-level multi-annual synchrony in open natural populations. Despite fences eliminating predatory mammals and vole dispersal, the growth rates of the experimental populations were synchronized and moreover, perfectly linked with vole abundance in the region. The fates of 481 radio-marked voles showed that bird predation was the synchronizing mechanism. A higher frequency of risky dispersal movements in slowly growing populations appeared to accelerate predation rate. Thus, dispersal may induce a feedback-loop between predation and population growth that enhances synchrony.
北欧田鼠种群呈现出大规模、空间同步的种群动态。这种种群同步的情况为区分种群调节的局部内在机制和区域外在机制提供了绝佳机会。对大规模调查数据的分析和理论建模已经表明了几种可能的同步机制。然而，没有关于局部种群动态过程的详细数据，就很难确定最重要的机制。在此，我们结合了挪威东南部两项实地研究的结果——一项研究确定了28个封闭实验种群中的局部种群动态机制和景观水平的年度同步性，另一项研究考察了开放自然种群中的区域水平多年同步性。尽管围栏排除了捕食性哺乳动物和田鼠扩散，但实验种群的增长率是同步的，而且与该地区田鼠数量完美相关。481只佩戴无线电标记的田鼠的命运表明，鸟类捕食是同步机制。在生长缓慢的种群中，风险扩散运动的频率较高，这似乎加快了捕食率。因此，扩散可能会在捕食和种群增长之间引发一个反馈循环，从而增强同步性。
