Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Aquatic Ecology, Uberlandstrasse 133, 8600 Dübendorf, Switzerland.
Ecology. 2009 Dec;90(12):3430-44. doi: 10.1890/08-0886.1.
Differential habitat selection is a central component in the evolution of species, but it has been quantified rarely for sympatric species in relation to the multiple impacts of resources at the spatial scales at which animals operate. Our main goal was to quantify the selection of terrestrial summer habitats in a natural floodplain in Italy by two sympatric amphibians (Bufo bufo spinosus and B. viridis) as a function of habitat type, prey density, and temperature. We applied a Bayesian resource selection model at three spatial scales: (1) home range placement within the floodplain, (2) space use within 95% home ranges, and (3) space use within 50% core areas. Using these data we explored whether processes acting at large scales lead to space use patterns at small scales and whether the two species use the same habitat types in a way that would facilitate coexistence. Habitat selection was determined by habitat type, prey density, and temperature at all spatial scales, resulting in slightly higher prey density and significantly lower temperature within than outside home ranges. We conclude that amphibians perceive the distribution of habitat types as well as gradients in prey density and temperature at all spatial scales. The effects of habitat type dominated home range placement while prey density and temperature most strongly affected space use within home ranges. Our results suggest that home range placement relies on broad habitat features that indicate resource availability at small spatial scales. At the smallest spatial scale, the selection of prey and refugia is most probably facilitated due to the accumulation of environmental information as animals may sample the entire area. Both species largely preferred the same habitat types, but used them differently in relation to resources across the three spatial scales. For example, while one species used the same habitat type for foraging, the other used it for resting or both resting and foraging. Niche differentiation through differential resource selection within shared habitat types at all spatial scales may therefore facilitate the coexistence of the two species in terrestrial summer habitats.
物种的进化中，差异生境选择是一个核心组成部分，但很少有研究将其量化为同域物种，以反映资源在动物活动的空间尺度上的多重影响。我们的主要目标是量化意大利自然洪泛平原中两种同域两栖动物（棘棱蟾蜍和绿蟾蜍）对陆生夏季栖息地的选择，这是作为对栖息地类型、猎物密度和温度的功能反应。我们在三个空间尺度上应用了贝叶斯资源选择模型：（1）在洪泛平原内的家域安置，（2）在 95%家域内的空间利用，以及（3）在 50%核心区域内的空间利用。利用这些数据，我们探讨了大尺度上的过程是否会导致小尺度上的空间利用模式，以及这两个物种是否以有利于共存的方式利用相同的栖息地类型。在所有空间尺度上，生境选择均由生境类型、猎物密度和温度决定，导致家域内的猎物密度略高，温度明显低于家域外。我们的结论是，两栖动物在所有空间尺度上都能感知栖息地类型的分布以及猎物密度和温度的梯度。生境类型的影响主导了家域的安置，而猎物密度和温度则对家域内的空间利用影响最大。我们的研究结果表明，家域的安置依赖于指示小空间尺度资源可利用性的广泛生境特征。在最小的空间尺度上，由于动物可能会对整个区域进行采样，因此对猎物和避难所的选择很可能会因环境信息的积累而得到促进。这两个物种主要偏好相同的栖息地类型，但在三个空间尺度上的资源利用方面使用方式不同。例如，一种物种使用相同的栖息地类型进行觅食，而另一种物种则将其用于休息或同时用于觅食和休息。因此，在所有空间尺度上通过在共享栖息地类型中进行差异资源选择来实现生态位分化，可能有助于这两个物种在陆生夏季栖息地中的共存。
