Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
PLoS One. 2009 Sep 18;4(9):e7071. doi: 10.1371/journal.pone.0007071.
The changes in phylogenetic composition and structure of communities during succession following disturbance can give us insights into the forces that are shaping communities over time. In abandoned agricultural fields, community composition changes rapidly when a field is plowed, and is thought to reflect a relaxation of competition due to the elimination of dominant species which take time to re-establish. Competition can drive phylogenetic overdispersion, due to phylogenetic conservation of 'niche' traits that allow species to partition resources. Therefore, undisturbed old field communities should exhibit higher phylogenetic dispersion than recently disturbed systems, which should be relatively 'clustered' with respect to phylogenetic relationships. Several measures of phylogenetic structure between plant communities were measured in recently plowed areas and nearby 'undisturbed' sites. There was no difference in the absolute values of these measures between disturbed and 'undisturbed' sites. However, there was a difference in the 'expected' phylogenetic structure between habitats, leading to significantly lower than expected phylogenetic diversity in disturbed plots, and no difference from random expectation in 'undisturbed' plots. This suggests that plant species characteristic of each habitat are fairly evenly distributed on the shared species pool phylogeny, but that once the initial sorting of species into the two habitat types has occurred, the processes operating on them affect each habitat differently. These results were consistent with an analysis of correlation between phylogenetic distance and co-occurrence indices of species pairs in the two habitat types. This study supports the notion that disturbed plots are more clustered than expected, rather than 'undisturbed' plots being more overdispersed, suggesting that disturbed plant communities are being more strongly influenced by environmental filtering of conserved niche traits.
演替过程中干扰后群落的系统发育组成和结构的变化，可以让我们深入了解塑造群落随时间变化的力量。在废弃的农田中，当田地被犁耕时，群落组成会迅速发生变化，这被认为反映了竞争的放松，因为优势物种被消除，它们需要时间重新建立。竞争会导致系统发育离散度增加，因为“生态位”特征的系统发育保守性允许物种分配资源。因此，未受干扰的旧农田群落应该表现出比最近受干扰的系统更高的系统发育离散度，而后者在系统发育关系上应该相对“聚集”。在最近犁耕的地区和附近的“未受干扰”地点测量了几种植物群落之间的系统发育结构措施。受干扰和“未受干扰”地点之间这些措施的绝对值没有差异。然而，生境之间的“预期”系统发育结构存在差异，导致受干扰的样方的系统发育多样性明显低于预期，而“未受干扰”的样方则与随机预期没有差异。这表明，每个栖息地特有的植物物种在共享物种库系统发育上的分布相当均匀，但一旦物种最初被分类为两种栖息地类型，作用于它们的过程就会以不同的方式影响它们。这些结果与两种栖息地类型中物种对之间系统发育距离和共现指数之间的相关性分析一致。这项研究支持了这样一种观点，即受干扰的样方比预期的更聚集，而不是“未受干扰”的样方更离散，这表明受干扰的植物群落受到保守生态位特征的环境过滤的影响更强。
