渔山岛岩礁基质潮间带大型底栖动物优势种生态位

2009年3月至2010年1月期间对渔山岛岩礁基质潮间带大型底栖动物进行定量采样调查，并获得大型底栖动物85种，筛选出全年取样获得优势种30种，隶属5门7纲24科。对获得的30个优势种以Shannon—Wiener指数为基础进行了生态位宽度测定，以Pianka重叠指数为基础进行了生态位重叠值分析，结果显示：潮间带大型底栖动物群落中优势种生态位宽度变化范围为0.18~1.94，值较高的有条纹隔贻贝、覆瓦小蛇螺、角偏顶蛤、日本笠藤壶、鳞笠藤壶和马氏毛粒蟹，均大于1.00，它们对环境适应的能力较强；各优势种的生态位重叠程度不均匀，在0~0.97之间，它们对群落环境资源的利用存在着交叉，潜在的种间竞争压力较大。以密度数据四次开方为基础，利用欧氏距离进行群落物种的系统聚类分析和非度量多维标度排序分析，结果均表明30个优势种可以分为三大类，即狭布种、泛化种和特有种。优势种生态位宽度、优势种之间的生态位重叠值与物种的分布与数量密切相关，生境相似程度高的物种聚类和排序距离就小，大型底栖动物主要通过在资源位上的分布、摄食类群和生活型等的差异缓解竞争。

Niche analysis of dominant species of macrobenthic community at a tidal flat of Yushan Island

The theory of niche breadth has played an important role in the study of community composition and function, of the relationships among species, biodiversity, community succession and population evolution since Grinnell proposed that niche breadth was the minimum unit of a population. Yushan Island belongs to an archipelago of 13 islands and 41 reefs southeast of Xiangshan, in Zhejiang province. To determine the composition of the intertidal macroinvertebrate communities of Yushan Island, quantitative surveys were conducted according to the National Standard, GB/T 12763.6-2007, from March 2009 to January 2010. Eighty-five species of macrobenthos were identified, including 30 dominant species belonging to 24 families, seven classes and five phyla. Most organisms were arthropods or mollusks. Shannon-Wiener's Niche Breadth (NB) index and the Pianka's Niche Overlap index were used to compare dominant species. NB was significantly different among species. Septifer virgatus, Serpulorbis imbricata, Modiolus modiolus, Tetraclita japonica, T. squamosa and Pilumnus minutus had large niche breadths (NB>1.00), while Littorina brevicula, Crepidula gravispinosa and Ophiura kinbergi had narrow niche breadths. The adaptabilities of the most dominant species to environmental conditions (NB >1.00) were higher than for other species (NB<1.00). The abundances of individuals of species restricted to conditions located only within a narrow intertidal section or to only certain seasons, for example L. brevicula, was higher, but the niche breadth of these species was not larger than the other species in the same restricted habitats. Thus niche breadth was related to habitat. Niche overlaps, which varied from 0 to 0.97, were impacted significantly by niche breadth and relative abundance. Tetraclita japonica and T. squamosa had a niche overlap close to 0.97. Thus it is likely that when these two species are located in the same portion of the middle intertidal zone, there is competition for substrate. Crepidula gravispinosa and Ophiura kinbergi were found in association with Mytilus coruscus; Corophium acherusicum and Clianella japonica, and both occupied burrows produced by mollusca. Acanthochiton rubrolineatus and Thais luteostoma also typically cohabited the same area. It is likely that space competition among the dominant species was intense since the niche overlap exceeded 0.9. Niche overlaps occurred between species with both low niche breadth and high niche breadth. Niche overlaps of zero indicated that the species did not inhabit that environmental site. Using hierarchical clustering with between-group linkage and non-metric multidimensional scaling, the 30 dominant species were classified into three groups: rare, common and special species. Spatial distribution, niche overlap, functional feeding differences and habitat differences were the principle strategies used by each species to reduce competition.