Department of Zoology, University of Oxford, South Parks Road, Oxford, UK.
ISME J. 2010 Nov;4(11):1357-65. doi: 10.1038/ismej.2010.77. Epub 2010 Jun 10.
Community similarity declines with increasing geographic distance if species tend to be locally adapted or if they are dispersal limited. The distance-decay of similarity has been shown for bacteria previously, but distinguishing between these competing mechanisms is difficult from observational surveys. I found little evidence of a relationship between geographic distance and similarity in community composition in an aquatic bacterial community. When bacterial colonization occurred into initially identical sterile microcosms across a woodland, a strong distance-decay relationship was observed after 28 days, implying that dispersal limitation created a strong pattern in these communities in the absence of environmental differences. This conclusion was not supported by the results of a reciprocal transplant experiment. When microcosms at the extremities of the study area were transplanted to the opposite end of the study area, the communities converged on the community composition at the site to which they were transplanted. This convergence did not depend on whether colonization into the microcosms was prevented, implying a minor role for dispersal limitation over these spatial and temporal scales. Additional manipulations of colonization rates were consistent with the hypothesis that dispersal limitation structured these communities over short time scales (a few days), but that dispersal limitation had a minor role over longer time scales (>7 days).
如果物种倾向于局部适应或受到扩散限制，那么随着地理距离的增加，群落的相似性就会下降。先前已经证明了细菌之间的相似性具有距离衰减的特征，但从观测调查中很难区分这些竞争机制。在一个水生细菌群落中，我几乎没有发现群落组成的地理距离与相似性之间存在关系的证据。当细菌在林地的无菌微宇宙中进行殖民时，在 28 天后观察到了强烈的距离衰减关系，这表明在没有环境差异的情况下，扩散限制在这些群落中产生了强烈的模式。这一结论与一项相互移植实验的结果不一致。当研究区域边缘的微宇宙被移植到研究区域的另一端时，群落会与它们被移植到的地点的群落组成趋同。这种趋同并不取决于是否阻止了微宇宙中的殖民，这意味着在这些空间和时间尺度上，扩散限制的作用较小。对殖民率的其他操作处理与以下假设一致，即扩散限制在短时间尺度（几天）上构建了这些群落，但在较长时间尺度（>7 天）上扩散限制的作用较小。
