Heske Edward J, Bondrup-Nielsen Søren
Department of Biology, University of New Mexico, 87131, Albuquerque, NM, USA.
Department of Biology, Division of Zoology, University of Oslo, Blindern, P.O. Box 1050, 0316, Oslo 3, Norway.
Oecologia. 1990 May;83(1):91-98. doi: 10.1007/BF00324639.
There are several published hypotheses that consider spacing behavior to be a significant factor causing the multiannual density fluctuations characteristic of some microtine rodent populations. Recent modeling efforts have concluded, however, that spacing behavior should have a stabilizing rather than a destabilizing effect on population dynamics. Why doesn't spacing behavior stabilize these cyclic populations? We argue that while spacing behavior does have a stabilizing influence on population dynamics by limiting the number of breeding individuals, reproduction continues and population size is not limited in an asymptotic manner. Rather, microtine social organization produces demographic changes within a population that allow density cycles to occur under certain conditions. Using a simulation model, we demonstrate that in a strongly seasonal environment populations with low density dependence in reproduction will cycle whereas populations with high density dependence in reproduction will have relatively stable densities. Given such complicating factors as the "annual species" nature of microtine rodents, occasionally intense predation, and the tendency for territoriality to break down during the non-breeding season, individuals with low density dependence in reproduction will always be able to invade and eventually dominate populations with high density dependence in reproduction, regardless of the resulting destabilization of population dynamics.
有几种已发表的假说认为，空间行为是导致某些田鼠种群出现多年密度波动特征的一个重要因素。然而，最近的建模研究得出结论，空间行为对种群动态应该具有稳定作用而非破坏稳定的作用。为什么空间行为不能使这些周期性种群趋于稳定呢？我们认为，虽然空间行为确实通过限制繁殖个体数量对种群动态具有稳定影响，但繁殖仍在继续，种群规模并未以渐近方式受到限制。相反，田鼠的社会组织会在种群内部产生人口结构变化，从而使得在某些条件下密度循环能够发生。我们使用一个模拟模型证明，在季节性强烈的环境中，繁殖中低密度依赖的种群会出现循环，而繁殖中高密度依赖的种群密度将相对稳定。鉴于田鼠具有“一年生物种”的特性、偶尔存在的强烈捕食以及在非繁殖季节领地性趋于瓦解等复杂因素，繁殖中低密度依赖的个体总是能够侵入并最终占据繁殖中高密度依赖的种群，无论这对种群动态会造成怎样的不稳定影响。
