Department of Biology, University of Puerto Rico, Mayagüez Campus, Mayagüez, PR 00682.
Microb Ecol. 2012 Jul;64(1):200-13. doi: 10.1007/s00248-011-0004-8.
The mechanisms that ultimately regulate the diversity of microbial eukaryotic communities in bryophyte ecosystems remain a contentious topic in microbial ecology. Although there is robust consensus that abiotic factors, such as water chemistry of the bryophyte and pH, explain a significant proportion of protist and microcrustacean diversity, there is no systematic assessment of the role of bryophyte habitat complexity on such prominent microbial groups. Water-holding capacity is correlated with bryophyte morphology and canopy structure. Similarly, canopy structure explains biodiversity dynamics of the macrobiota suggesting that canopy structure may also be a potential parameter for understanding microbial diversity. Canopy roughness of the dominant bryophyte species within the Bahoruco Cloud Forest, Cachote, Dominican Republic, concomitant with their associated diversity of testate amoebae and microcrustaceans was estimated to determine whether canopy structure could be added to the list of factors explaining microbial biodiversity in bryophytes. We hypothesized that smooth (with high moisture content) canopies will have higher species richness, density, and biomass of testate amoebae and higher richness and density of microcrustaceans than rough (desiccation-prone) canopies. For testate amoebae, we found 83 morphospecies with relative low abundances. Species richness and density differed among bryophytes with different bryophyte canopy structures and based on non-metric multidimensional scaling, canopy roughness explained 25% of the variation in species composition although not as predicted. Acroporium pungens (low roughness, LR) had the lowest species richness (2 ± 0.61 SD per gram dry weight bryophyte), and density (2.1 ± 0.61 SD individual per gram of dry weight bryophyte); whereas Thuidium urceolatum (high roughness) had the highest richness (24 ± 10.82 SD) and density (94 ± 64.30 SD). The fact that the bryophyte with the highest roughness had the highest levels of diversity for testate amoebae suggests that moisture levels at the level of the bryophyte canopy may not represent a biodiversity driver in a cloud forest with high relative humidity; however, high roughness could generate a dynamic and fluctuating moisture environment with concomitant alternating microbial communities. A total of 26 microcrustacean morphospecies were found across 11 bryophytes; however, no bryophyte canopy effect was detected on their richness and density. Microcrustacean mean density was low ranging from less than one individual per 50 cm2 of bryophyte in Leucobryum (LR) to a maximum of 6 ± 3.37 SD individuals/50 cm2 in Monoclea (LR). This lack of pattern suggests that possible explanatory variables may be related to larger scale processes than those examined in this study.
在苔藓植物生态系统中，最终调节微生物真核生物群落多样性的机制仍然是微生物生态学中的一个有争议的话题。尽管人们普遍认为，非生物因素，如苔藓植物的水化学和 pH 值，解释了原生动物和微型甲壳类动物多样性的很大一部分，但对于苔藓植物栖息地复杂性对这些突出微生物群的作用，并没有系统的评估。持水能力与苔藓植物的形态和冠层结构有关。同样，冠层结构解释了大型生物多样性的动态变化，表明冠层结构也可能是理解微生物多样性的一个潜在参数。在多米尼加共和国 Bahoruco 云雾林的 Cachote，对主要苔藓物种的冠层粗糙度进行了评估，同时还评估了与之相关的有孔虫和微型甲壳类动物的多样性，以确定冠层结构是否可以添加到解释苔藓植物中微生物生物多样性的因素列表中。我们假设，光滑（水分含量高）的冠层将比粗糙（易干燥）的冠层具有更高的有孔虫物种丰富度、密度和生物量，以及更高的微型甲壳类动物丰富度和密度。对于有孔虫，我们发现了 83 种形态物种，相对丰度较低。具有不同苔藓植物冠层结构的苔藓植物之间的物种丰富度和密度存在差异，基于非度量多维尺度分析，冠层粗糙度解释了物种组成变化的 25%，尽管与预测的结果不一致。Acroporium pungens（低粗糙度，LR）的物种丰富度最低（每克干重苔藓植物 2 ± 0.61 SD），密度最低（每克干重苔藓植物 2.1 ± 0.61 SD 个体）；而 Thuidium urceolatum（高粗糙度）的物种丰富度最高（24 ± 10.82 SD），密度最高（94 ± 64.30 SD）。具有最高粗糙度的苔藓植物具有最高水平的有孔虫多样性，这表明在相对湿度较高的云雾林中，苔藓植物冠层的水分水平可能不是生物多样性的驱动因素；然而，高粗糙度可能会产生动态波动的水分环境，并伴随着交替的微生物群落。在 11 种苔藓植物中发现了总共 26 种微型甲壳类动物形态物种；然而，在它们的丰富度和密度方面没有检测到苔藓植物冠层的影响。微型甲壳类动物的平均密度较低，每 50 平方厘米苔藓植物中不到一个个体，Leucobryum（LR）中最低，每 50 平方厘米中最多 6 ± 3.37 SD 个个体/Monoclea（LR）。这种没有模式的情况表明，可能的解释变量可能与本研究中检查的更大规模过程有关。
