INTERSPECIFIC COMPETITION AND NICHE CHANGES IN TITS (PARUS SPP) - EVALUATION OF NONEXPERIMENTAL DATA
INTERSPECIFIC COMPETITION AND NICHE CHANGES IN TITS (PARUS SPP) - EVALUATION OF NONEXPERIMENTAL DATA
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DOI：
10.1086/284527
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发表时间：
1986-06-01
影响因子：
2.9
通讯作者：
LUNDBERG, A
中科院分区：
文献类型：
--
作者：
ALATALO, RV;GUSTAFSSON, L;LUNDBERG, A
在当前的“竞争争议”中，非实验观察对于测试因果过程（例如种间竞争）的作用受到了质疑。最初，异源和同源区域之间的生态位变化被认为是种间竞争的有力证据。然而，任何单一的变化都可能是由于其他原因造成的，特别是环境的差异，无论假定的竞争对手是否存在。我们评估了欧洲山雀（Parus spp.）的生态位变化。在所有七个研究案例中，一两个物种在共生区域表现出明显的、不同的生态转变。同样，Alatalo（1981）发现，与单一物种的山雀群相比，混合物种山雀群的觅食地点存在普遍差异。在存在假定竞争对手的情况下，这些显着的趋向于发散而不是趋同的转变不能仅用环境差异来解释。种间竞争导致生态位变化的最有力证据来自观察，即在行会内部，仅在形态上与异域繁殖中不存在的物种最相似的物种中发现了变化（重量比≤1.2）。一般来说，我们认为，如果可行的话，做得好的实验是评估替代假设的最佳方法。然而，如果可以反驳观察到的模式的替代解释，那么也可以在不进行实验的情况下对因果过程做出推断。非实验方法很乏味，需要对动物和所考虑的问题有很好的了解。包含几个允许进行一般测试的独立比较具有很大的价值。
The role of nonexperimental observations for testing causal processes, such as interspecific competition, has been questioned during the present "competition controversy." Initially, niche changes between areas of allopatry and sympatry were considered to be strong evidence for interspecific competition. However, any single change may be due to alternative causes, in particular, to differences in the environment irrespective of the presence or absence of the putative competitor. We evaluated niche changes in European tits (Parus spp.). In all seven cases studied, one or two species showed a clear, divergent ecological shift in the area of sympatry. Likewise, Alatalo (1981) found a general pattern of divergence in foraging sites in mixed-species tit flocks compared with monospecific flocks. These significant tendencies toward divergent rather than convergent shifts in the presence of putative competitors cannot be explained by differences in the environment alone. The strongest evidence that interspecific competition causes niche changes comes from the observation that, within the guild, changes were found only in the species that morphologically most closely resembled the species that were absent in allopatry (weight ratio .ltoreq. 1.2). In general, we believe that well-done experiments, if feasible, are the best way to evaluate alternative hypotheses. However, it is also possible to make inferences about causal processes without experiments if alternative explanations of the observed patterns can be refuted. The nonexperimental approach is tedious and requires good knowledge of the animals and the question under consideration. Inclusion of several independent comparisons allowing general tests is of great value.