Hillebrand Helmut, Watermann Frank, Karez Rolf, Berninger Ulrike-G
Erkenlaboratory, Department of Limnology, EBC, Uppsala University, Norr Malma 4200, 76173, Norrtaelje, Sweden.
Institute of Chemistry and Biology of the Marine Environment, Marine Station, Schleusenstrasse 1, 26382, Wilhelmshaven, Germany.
Oecologia. 2001 Jan;126(1):114-124. doi: 10.1007/s004420000492. Epub 2001 Jan 1.
For unicellular organisms, a lack of effects of local species richness on ecosystem function has been proposed due to their locally high species richness and their ubiquitous distribution. High dispersal ability and high individual numbers may enable unicellular taxa to occur everywhere. Using our own and published data sets on uni- and multicellular organisms, we conducted thorough statistical analyses to test whether (1) unicellular taxa show higher relative local species richness compared to multicellular taxa, (2) unicellular taxa show lower slopes of the species:area relationships and species:individuals relationships, and (3) the species composition of unicellular taxa is less influenced by geographic distance compared to multicellular taxa. We found higher local species richness compared to the global species pool for unicellular organisms than for metazoan taxa. The difference was significant if global species richness was conservatively estimated but not if extrapolated, and therefore higher richness estimates were used. Both microalgae and protozoans showed lower slopes between species richness and sample size (area or individuals) compared to macrozoobenthos, also indicating higher local species richness for unicellular taxa. The similarity of species composition of both benthic diatoms and ciliates decreased with increasing geographic distance. This indicated restricted dispersal ability of protists and the absence of ubiquity. However, a steeper slope between similarity and distance was found for polychaetes and corals, suggesting a stronger effect of distance on the dispersal of metazoans compared to unicellular taxa. In conclusion, we found partly different species richness patterns among uni- and multicellular eukaryotes, but no strict ubiquity of unicellular taxa. Therefore, the effect of local unicellular species richness on ecosystem function has to be reanalyzed. Macroecological patterns suggested for multicellular organisms may differ in unicellular communities.
对于单细胞生物，由于其局部物种丰富度高且分布广泛，有人提出局部物种丰富度对生态系统功能缺乏影响。高扩散能力和大量个体数量可能使单细胞类群能够在任何地方出现。利用我们自己以及已发表的关于单细胞和多细胞生物的数据集，我们进行了全面的统计分析，以检验：（1）与多细胞类群相比，单细胞类群是否表现出更高的相对局部物种丰富度；（2）单细胞类群的物种 - 面积关系和物种 - 个体关系的斜率是否更低；（3）与多细胞类群相比，单细胞类群的物种组成受地理距离的影响是否更小。我们发现，与后生动物类群相比，单细胞生物的局部物种丰富度高于全球物种库。如果保守估计全球物种丰富度，差异是显著的，但如果采用外推估计则不显著，因此我们使用了更高的丰富度估计值。与大型底栖动物相比，微藻和原生动物在物种丰富度与样本量（面积或个体数量）之间的斜率更低，这也表明单细胞类群的局部物种丰富度更高。底栖硅藻和纤毛虫的物种组成相似度随地理距离增加而降低。这表明原生生物的扩散能力有限且并非无处不在。然而，多毛类动物和珊瑚在相似度与距离之间的斜率更陡，这表明与单细胞类群相比，距离对后生动物扩散的影响更强。总之，我们发现单细胞和多细胞真核生物之间存在部分不同的物种丰富度模式，但单细胞类群并非严格无处不在。因此，必须重新分析局部单细胞物种丰富度对生态系统功能的影响。针对多细胞生物提出的宏观生态模式在单细胞群落中可能有所不同。
