Peguero Guille, Ferrín Miquel, Sardans Jordi, Verbruggen Erik, Ramírez-Rojas Irene, Van Langenhove Leandro, Verryckt Lore T, Murienne Jerome, Iribar Amaia, Zinger Lucie, Grau Oriol, Orivel Jerome, Stahl Clément, Courtois Elodie A, Asensio Dolores, Gargallo-Garriga Albert, Llusià Joan, Margalef Olga, Ogaya Romà, Richter Andreas, Janssens Ivan A, Peñuelas Josep
Departament de Biologia Animal, Biologia Vegetal i Ecologia, Universitat Autònoma de Barcelona, 08193, Bellaterra, Spain.
CSIC, Global Ecology Unit CREAF-CSIC-UAB, 08913, Bellaterra, Spain.
Ecology. 2022 Feb;103(2):e03599. doi: 10.1002/ecy.3599. Epub 2021 Dec 28.
Understanding the mechanisms that drive the change of biotic assemblages over space and time is the main quest of community ecology. Assessing the relative importance of dispersal and environmental species selection in a range of organismic sizes and motilities has been a fruitful strategy. A consensus for whether spatial and environmental distances operate similarly across spatial scales and taxa, however, has yet to emerge. We used censuses of four major groups of organisms (soil bacteria, fungi, ground insects, and trees) at two observation scales (1-m sampling point vs. 2,500-m plots) in a topographically standardized sampling design replicated in two tropical rainforests with contrasting relationships between spatial distance and nutrient availability. We modeled the decay of assemblage similarity for each taxon set and site to assess the relative contributions of spatial distance and nutrient availability distance. Then, we evaluated the potentially structuring effect of tree composition over all other taxa. The similarity of nutrient content in the litter and topsoil had a stronger and more consistent selective effect than did dispersal limitation, particularly for bacteria, fungi, and trees at the plot level. Ground insects, the only group assessed with the capacity of active dispersal, had the highest species turnover and the flattest nonsignificant distance-decay relationship, suggesting that neither dispersal limitation nor nutrient availability were fundamental drivers of their community assembly at this scale of analysis. Only the fungal communities at one of our study sites were clearly coordinated with tree composition. The spatial distance at the smallest scale was more important than nutrient selection for the bacteria, fungi, and insects. The lower initial similarity and the moderate variation in composition identified by these distance-decay models, however, suggested that the effects of stochastic sampling were important at this smaller spatial scale. Our results highlight the importance of nutrients as one of the main environmental drivers of rainforest communities irrespective of organismic or propagule size and how the overriding effect of the analytical scale influences the interpretation, leading to the perception of greater importance of dispersal limitation and ecological drift over selection associated with environmental niches at decreasing observation scales.
理解驱动生物群落随空间和时间变化的机制是群落生态学的主要研究目标。评估扩散和环境物种选择在一系列生物体大小和移动性中的相对重要性是一种富有成效的策略。然而，关于空间和环境距离在不同空间尺度和分类群中是否以相似方式起作用，尚未形成共识。我们在两个地形标准化的观测尺度（1米采样点与2500米样地）上，对四大类生物体（土壤细菌、真菌、地面昆虫和树木）进行了普查，该采样设计在两个热带雨林中重复进行，这两个雨林在空间距离和养分有效性之间具有不同的关系。我们对每个分类群集和地点的群落相似性衰减进行建模，以评估空间距离和养分有效性距离的相对贡献。然后，我们评估了树木组成对所有其他分类群的潜在结构效应。凋落物和表土中养分含量的相似性比扩散限制具有更强、更一致的选择效应，特别是在样地水平上对细菌、真菌和树木而言。地面昆虫是唯一被评估具有主动扩散能力的类群，其物种周转率最高，距离衰减关系最平缓且无显著意义，这表明在这个分析尺度上，扩散限制和养分有效性都不是其群落组装的基本驱动因素。在我们的一个研究地点，只有真菌群落与树木组成明显相关。对于细菌、真菌和昆虫来说，最小尺度的空间距离比养分选择更重要。然而，这些距离衰减模型所确定的较低初始相似性和组成的适度变化表明，随机抽样效应在这个较小的空间尺度上很重要。我们的结果强调了养分作为热带雨林群落主要环境驱动因素之一的重要性，而不论生物体或繁殖体的大小如何，以及分析尺度的主导效应如何影响解释，导致在观测尺度减小的情况下，人们认为扩散限制和生态漂变比与环境生态位相关的选择更为重要。
