中文摘要：

树生苔藓是反映大气污染有效指示体，在这些苔藓上附着大量的硅藻，但目前对这些硅藻属种组成及其生态属性了解很少。为此，本文在武汉市主要公园和校园以及大九湖自然保护区（用于对比）乔木上共采集26个附生苔藓样本，同时记录树种和苔藓属种，并进行硅藻属种鉴定统计分析。调查共发现13属73种附生苔藓硅藻，其中羽纹纲Luticola mutica、Pinnularia borealis和Hantzschia amphioxys是主要优势种。7个样本中硅藻属种数超过10种，表明在附生苔藓具有较高的硅藻物种丰富度。主成分分析和聚类分析结果表明，26个样本可分为3个类群：以L. mutica为优势种的组合，以H. amphioxys和Humidophila contenta为优势种的组合，和以P. borealis为优势种的组合。这些主要优势种均为全球广泛分布的耐旱属种，耐旱种的大量出现主要响应于树皮干旱生境。将26个样本分别按照不同树种、苔藓属种和地区分组，相似性分析结果表明，硅藻与苔藓并无特定的附着关系，而树种可能是影响硅藻组成的因素之一。此外，武汉市和大九湖的硅藻组成差异显著。本研究揭示了附生苔藓硅藻组合特征，为深入了解陆生硅藻生物多样性及其环境指示意义奠定了基础。

英文摘要：

Epiphytic bryophytes on trees are a useful indicator of air pollution and they provide habitats for a large number of diatoms. Until now, little knowledge is available about these diatoms and their autoecology. In this paper, twentytwo epiphytic bryophyte samples on trees from the main parks and campuses in Wuhan City and four samples from Dajiuhu National Natural Reserve （for comparison） were collected for diatom analysis, in combination with tree and bryophyte identifications. In total, 13 genera and 73 species of diatoms were identified, which were dominated by three Pennatae taxa, i.e. Luticola mutica, Pinnularia borealis and Hantzschia amphioxys. Seven samples had more than 10 diatom species within each sample, indicating high diatom richness in epiphytic bryophytes. Three clusters were identified by principal component analysis and clustering analysis, including one dominated by L. mutica, a second with H. amphioxys and Humidophila contenta codominated assemblages, and a third dominated by the diatom P. borealis. All of these dominant diatom species are cosmopolitan droughttolerant species. The high abundance of droughttolerant species was mainly responsive to dry conditions on tree bark. Twentysix samples were divided into different groups according to their host tree species and bryophyte species and locations, respectively. The ANOSIM analysis revealed that there was no parasitehost relationship between diatoms and bryophytes, but tree species might influence diatom composition. Diatom communities in Wuhan City were significantly different from those in Dajiuhu National Natural Reserve. The results revealed the characteristics of epiphytic diatom composition on epiphytic bryophytes, thus improving our knowledge about the biodiversity of terrestrial diatoms and their potential as an environmental indicator.