Huitu Otso, Norrdahl Kai, Korpimäki Erkki
Section of Ecology, Department of Biology, University of Turku, 20014 Turku, Finland.
Oecologia. 2003 Apr;135(2):209-20. doi: 10.1007/s00442-002-1171-6. Epub 2003 Feb 20.
Populations of northern small rodents have previously been observed to fluctuate in spatial synchrony over distances ranging from tens to hundreds of kilometers between sites. It has been suggested that this phenomenon is caused by common environmental perturbations, mobile predators or dispersal movements. However, very little focus has been given to how the physical properties of the geographic area over which synchrony occurs, such as landscape composition and climate, affect spatial population dynamics. This study reports on the spatial and temporal properties of vole population fluctuations in two areas of western Finland: one composed of large interconnected areas of agricultural farmland interspersed by forests and the other highly dominated by forest areas, containing more isolated patches of agricultural land. Furthermore, the more agricultural area exhibits somewhat milder winters with less snow than the forested area. We found the amplitude of vole cycles to be essentially the same in the two areas, suggesting that the relative amount of predation on small rodents by generalist versus specialist predators is similar in both areas. No seasonal differences in the timing of synchronization were observable for Microtus voles, whereas bank vole populations in field habitats appeared to become synchronized primarily during winter. Microtus populations in field habitats exhibited smaller spatial variation and a higher degree of synchrony in the more continuous agricultural landscape than in the forest-dominated landscape. We suggest that this inter-areal difference is due to differences in the degree of inter-patch connectivity, with predators and dispersal acting as the primary synchronizing agents. Bank vole populations in field habitats were more synchronized within the forest-dominated landscape, most likely reflecting the suitability of the inter-patch matrix and the possibility of dispersal. Our study clearly indicates that landscape composition needs to be taken into account when describing the spatial properties of small rodent population dynamics.
此前曾观察到，北方小型啮齿动物种群在不同地点之间数十至数百公里的距离上呈现空间同步波动。有人认为，这种现象是由常见的环境扰动、流动的捕食者或扩散运动引起的。然而，对于同步发生的地理区域的物理特性，如景观组成和气候，如何影响空间种群动态，却很少有人关注。本研究报告了芬兰西部两个地区田鼠种群波动的时空特性：一个地区由大片相互连接的农田区域组成，其间散布着森林；另一个地区则以森林为主，包含更多孤立的农田斑块。此外，农业区域较多的地区冬季比森林地区略温和，降雪量也较少。我们发现，两个地区田鼠种群数量波动的幅度基本相同，这表明两个地区中，广谱捕食者与专性捕食者对小型啮齿动物的捕食相对数量相似。对于水田鼠来说，同步时间没有季节性差异，而田野栖息地的棕背䶄种群似乎主要在冬季实现同步。田野栖息地的水田鼠种群在更连续的农业景观中比在森林为主的景观中表现出更小的空间变异和更高的同步程度。我们认为，这种地区间差异是由于斑块间连通程度的不同，捕食者和扩散起到了主要的同步作用。田野栖息地的棕背䶄种群在森林为主的景观中同步性更高，这很可能反映了斑块间基质的适宜性和扩散的可能性。我们的研究清楚地表明，在描述小型啮齿动物种群动态的空间特性时，需要考虑景观组成。
