Dickman C R
Department of Zoology, Australian National University, P.O. Box 4, 2601, Canberra, A.C.T., Australia.
Oecologia. 1986 Nov;70(4):536-543. doi: 10.1007/BF00379900.
An investigation was made of the effects of reducing and enhancing the intensity of competition on a small marsupial, Antechinus stuartii, from a larger and competitively dominant congener, A. swainsonii. Populations of these species were monitored in two study areas (one control, one experimental) in forest near Canberra, Australia, between February and July in 1980 and 1981. In the experimental study area in 1980 I reduced the numbers of A. swainsonii relative to A. stuartii (thus reducing the intensity of interspecific competition), but in 1981 I augmented the numbers of A. swainsonii (thus increasing the intensity of competition). No manipulations were made in the control study area, and the numbers of both species remained similar there in both years. When the intensity of interspecific competition was reduced, the A. stuartii population increased in size. Increases occurred also in individual movements, home range areas, diurnal activity and in the proportion of large terrestrial prey (larvae, Amphipoda) in the diet. An increase in use of structurally complex forest floor habitats also coincided with decreased arboreal activity. In contrast, when the intensity of competition was enhanced, most of these population and resource shifts were reversed. These findings suggest that reduction in the intensity of interspecific competition allows A. stuartii access to terrestrial sources of food favoured by A. swainsonii, whereas enhancement leads to exclusion of A. stuartii from the forest floor. Competition occurs by interference. This may result in fixed per capita competitive effects of A. swainsonii on A. stuartii, and account for the observed changes in a very broad range of population and resource parameters.
对减少和增强竞争强度对一种小型有袋动物——斯氏宽足袋鼩（Antechinus stuartii）的影响进行了调查，该有袋动物来自体型更大且在竞争中占优势的同属物种——斯文森宽足袋鼩（A. swainsonii）。1980年和1981年2月至7月期间，在澳大利亚堪培拉附近森林的两个研究区域（一个对照区，一个试验区）对这些物种的种群进行了监测。1980年在试验区，我减少了斯文森宽足袋鼩相对于斯氏宽足袋鼩的数量（从而降低种间竞争强度），但在1981年我增加了斯文森宽足袋鼩的数量（从而增加竞争强度）。对照研究区域未进行任何操作，这两个物种的数量在这两年中都保持相似。当种间竞争强度降低时，斯氏宽足袋鼩的种群数量增加。个体活动、家域面积、日间活动以及饮食中大型陆生猎物（幼虫、双甲目动物）的比例也有所增加。对结构复杂的森林地面栖息地利用的增加也与树栖活动的减少同时出现。相反，当竞争强度增强时，这些种群和资源转移大多发生逆转。这些发现表明，种间竞争强度的降低使斯氏宽足袋鼩能够获取斯文森宽足袋鼩所偏好的陆生食物来源，而竞争强度的增强则导致斯氏宽足袋鼩被排除在森林地面之外。竞争通过干扰发生。这可能导致斯文森宽足袋鼩对斯氏宽足袋鼩产生固定的人均竞争效应，并解释了在非常广泛的种群和资源参数中观察到的变化。
