Phyllosphere Fungal Communities Differentiate More Thoroughly than Bacterial Communities Along an Elevation Gradient
Phyllosphere Fungal Communities Differentiate More Thoroughly than Bacterial Communities Along an Elevation Gradient
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DOI：
10.1007/s00248-016-0742-8
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发表时间：
2016-03
影响因子：
3.6
通讯作者：
C. Vacher;T. Cordier;J. Vallance
中科院分区：
文献类型：
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作者：
C. Vacher;T. Cordier;J. Vallance
生态群落相似性的距离衰减模式已经被生态学家认识了几十年[1]。这种模式已经在各种大型有机体和微生物中显示[2-5]，包括叶际细菌群落[6]。它是由四个生态进化过程产生的：选择、漂移、扩散和突变[2，7]。选择和漂变导致了成分相似性随地理距离的衰减，而扩散则抵消了这种衰减[2]。突变降低了位置之间的相似性，而不管它们之间的距离[2]。因此，预计距离衰减曲线的形状在物种的分类或功能组之间会有所不同[8]。例如，细菌等较小的物种群体由于其较高的传播能力，预计距离衰减较慢。由于它们的突变率较高，因此预计它们在给定位置的样品中具有较低的组成相似性[9]。在这里，我们比较了真菌和细菌群落沿着海拔梯度的距离衰减曲线。因为细菌细胞（直径只有几微米）比最小的真菌个体小（单细胞酵母，直径数十微米）[9]，我们假设（i）像真菌一样，细菌群落沿着海拔梯度分化，但（ii）它们分化得不那么彻底（即，他们有一个较慢的距离衰减），和（iii）他们显示较低水平的组成相似性之间的样本，每个海拔。为了验证这些假设，我们比较了欧洲山毛榉（Fagus sylvatica L.）叶圈沿着海拔梯度从488米延伸到1533米，距离为23公里。抽样设计由12个样本组成，对应于4个海拔地点，每个地点3个林地[10]。先前的分析显示真菌群落组成沿着海拔梯度有相当大的变化，这表明气候条件（特别是温度）的选择驱动了叶际真菌群落组成的变化[10]。在这里，我们通过对先前用于测序真菌内部转录间隔区的相同样品中的细菌16 S rDNA进行454焦磷酸测序，表征了沿着沿着相同海拔梯度的细菌群落[10]。生物信息学分析详见表S1。为了避免由于两个条形码区域之间序列变异性的差异而导致的偏差，使用四个同一性截止阈值（90、95、97和99%）将序列聚类成操作分类单位（OTU）。
The distance-decay pattern of similarity in ecological communities has been recognized by ecologists for decades [1]. Such a pattern has been shown for diverse macroorganisms and microorganisms [2–5], including phyllosphere bacterial communities [6]. It results from four eco-evolutionary processes: selection, drift, dispersal and mutation [2, 7]. Selection and drift generate the decay in compositional similarity with geographical distance, while dispersal counteracts it [2]. Mutation decreases the similarity among locations, regardless of the distance between them [2]. The shape of a distance-decay curve is therefore expected to differ between taxonomic or functional groups of species [8]. For instance, groups of smaller species such as bacteria are expected to have a slower distance-decay because of their higher dispersal abilities. They are also expected to have a lower compositional similarity among samples of a given location, because of their higher rates of mutation [9]. Here, we compared the distance-decay curves of fungal and bacterial communities along an elevation gradient. Since bacterial cells (with a diameter of a couple of micrometers) are smaller than the smallest fungal individuals (unicellular yeasts, measuring tens of micrometers across)[9], we hypothesized that (i) like fungi, bacterial communities differentiate along the elevation gradient, but (ii) they differentiate less thoroughly (ie, they have a slower distance-decay), and (iii) they display lower levels of compositional similarity among samples of each elevation. To test these hypotheses, we compared the distancedecay curves of fungal and bacterial communities inhabiting the European beech (Fagus sylvatica L.) phyllosphere along an elevation gradient extending from 488 to 1533 m over a distance of 23 km. The sampling design was composed of 12 samples, corresponding to 4 elevation sites with 3 forest plots per site [10]. Previous analyses showed considerable variation of the fungal community composition along the elevation gradient, suggesting that selection by climatic conditions (temperature, in particular) drives variations in the composition of phyllosphere fungal communities [10]. Here, we characterized the bacterial communities along the same elevation gradient, by 454 pyrosequencing the bacterial 16S rDNA in the same samples that had been used previously for sequencing the fungal internal transcribed spacer region [10]. Bioinformatic analyses are detailed in Table S1. To avoid biases due to differences in sequence variability between both barcode regions, sequence clustering into operational taxonomic units (OTUs) was performed using four identity cutoff thresholds (90, 95, 97, and 99%).