Hansen T F, Stenseth N C, Henttonen H, Tast J
University of Oslo, Department of Biology, Division of Zoology, P.O. Box 1050, Blindern, N-0316 Oslo, Norway.
Proc Natl Acad Sci U S A. 1999 Feb 2;96(3):986-91. doi: 10.1073/pnas.96.3.986.
A 3- to 5-year cycle of vole abundances is a characteristic phenomenon in the ecology of northern regions, and their explanation stands as a central theoretical challenge in population ecology. Although many species of voles usually coexist and are in severe competition for food and breeding space, the role of interspecific competition in vole cycles has never been evaluated statistically. After studying community effects on the population dynamics of the gray-sided vole (Clethrionomys rufocanus) in the subarctic birch forest at Kilpisjärvi, Finland, we report statistical results showing that both interspecific and intraspecific effects are important in the direct year-to-year density dependence. However, interspecific effects are not detectable in the 2-year delayed density dependence that is crucial for generating the characteristic cycles. Furthermore, we show that most of the competition takes place during the winter. The results are evaluated against two models of community dynamics. One assumes that the delayed effects are caused by an interaction with a specialist predator, and the other assumes that they are caused by overgrazing food plants. These statistical results show that vole cycles may be generated by a species-specific trophic interaction. The results also suggest that the gray-sided vole may be the focal species in the birch-forest community, as field voles may be in the taiga and as lemmings may be on the tundra.
田鼠数量呈现3至5年的周期性变化，这是北方地区生态系统中的一种典型现象，而对其作出解释一直是种群生态学的核心理论挑战。尽管许多田鼠物种通常共存，且在食物和繁殖空间方面存在激烈竞争，但种间竞争在田鼠数量周期中的作用从未得到过统计学评估。在对芬兰基尔皮斯耶尔维亚北极桦树林中灰侧田鼠（棕背䶄）种群动态的群落效应进行研究后，我们报告的统计结果表明，种间和种内效应在直接的逐年密度依赖性中都很重要。然而，在对产生典型周期至关重要的两年延迟密度依赖性中，种间效应并不明显。此外，我们发现大部分竞争发生在冬季。我们依据两种群落动态模型对结果进行了评估。一种模型假定延迟效应是由与一种专性捕食者的相互作用引起的，另一种模型假定是由过度啃食食用植物引起的。这些统计结果表明，田鼠数量周期可能是由特定物种的营养相互作用产生的。结果还表明，灰侧田鼠可能是桦树林群落中的关键物种，就像田鼠在泰加林可能是关键物种，旅鼠在冻原可能是关键物种一样。
