Faculty of Applied Ecology and Agricultural Science, Hedmark University College, Koppang, Norway.
Oecologia. 2013 Sep;173(1):161-7. doi: 10.1007/s00442-013-2614-y. Epub 2013 Feb 27.
The crash phase of vole populations with cyclic dynamics regularly leads to vast areas of uninhabited habitats. Yet although the capacity for cyclic voles to re-colonize such empty space is likely to be large and predicted to have become evolved as a distinct life history trait, the processes of colonization and its effect on the spatio-temporal dynamics have been little studied. Here we report from an experiment with root voles (Microtus oeconomus) specifically targeted at quantifying the process of colonization of empty patches from distant source patches and its resultant effect on local vole deme size variation in a patchy landscape. Three experimental factors: habitat quality, predation risk and inter-patch distance were employed among 24 habitat patches in a 100 × 300-m experimental area. The first-born cohort in the spring efficiently colonized almost all empty patches irrespective of the degree of patch isolation and predation risk, but this was dependent on habitat quality. Just after the initial colonization wave the deme sizes in patches of the same quality were underdispersed relative to Poisson variance, indicating regulated (density-dependent) settlement. Towards the end of the breeding season local demographic processes acted to smooth out the initial post-colonization differences among source and colonization patches, and among patches of initially different quality. However, at this time demographic stochasticity had also given rise to a large (overdispersed) variation in deme sizes that may have contributed to an overshadowing of the effect of other factors. The results of this experiment confirmed our expectation that the space-filling capacity of voles is large. The costs associated with transience appeared to be so low, at least at the spatial scale considered in this experiment, that such costs are not likely to substantially constrain habitat selection and colonization in the increase phase of cyclic patchy populations.
具有周期性动态的田鼠种群的崩溃阶段经常导致大片无人居住的栖息地。然而，尽管周期性田鼠重新定居这些空旷空间的能力可能很大，并预测已经进化为一种独特的生活史特征，但对定居过程及其对时空动态的影响的研究却很少。在这里，我们报告了一项针对根田鼠（Microtus oeconomus）的实验结果，该实验专门用于量化从遥远的源斑块中殖民空旷斑块的过程及其对斑块状景观中局部田鼠种群大小变化的影响。在一个 100×300 米的实验区域内的 24 个栖息地斑块中，我们使用了三个实验因素：栖息地质量、捕食风险和斑块间距离。在春季，第一只出生的田鼠幼崽几乎可以有效地殖民所有空旷的斑块，而不论斑块的隔离程度和捕食风险如何，但这取决于栖息地的质量。在初始殖民浪潮之后，同一质量的斑块中的种群大小相对泊松方差呈欠分散，表明存在受调节（密度依赖）的定居。在繁殖季节的后期，局部的人口过程作用于消除初始殖民后源斑块和殖民斑块之间以及最初不同质量斑块之间的差异。然而，此时人口随机性也导致种群大小出现了很大的（过分散）变化，这可能掩盖了其他因素的影响。该实验的结果证实了我们的预期，即田鼠的空间填充能力很大。过渡相关的成本似乎很低，至少在本实验考虑的空间尺度内是如此，以至于这些成本不太可能在周期性斑块种群的增加阶段对栖息地选择和定居产生实质性的限制。
