南麂列岛潮间带大型底栖动物群落优势种生态位

为了解南麂列岛潮间带大型底栖动物的群落特征及其物种间相互作用情况,于2012年5月至2013年2月对南麂列岛保护区内的12个资源位点(潮间带3个潮区的4个季节采样)进行了调查。共采集和鉴定出大型底栖动物354种,其中,18个优势种分别隶属于3门5纲12科。通过对优势种生态位的宽度、重叠度和相似比例的分析,发现:1)带偏顶蛤Modiolus comptus、条纹隔贻贝Septifer virgatus和异须沙蚕Nereis heterocirrata的生态位宽度较宽,均大于0.9;白条地藤壶Euraphia withersi和白脊藤壶Fistulobalanus albicostatus的生态位宽度则较窄,均小于0.5。2)各优势种群的生态位重叠度较低而生态位相似比例较高,生态位宽度值较高的物种对其他物种的生态位重叠值和生态位相似比例也较高,反之则较低。3)Bray-Curtis相似性聚类分析和非度量多维尺度排序(NMDS)结果表明,这些优势种基本属于同一生态类群,没有表现出明显的群落差异。经分析,潮间带大型底栖动物各优势种生态位宽度的分化是由于其对环境的适应能力和迁移能力的不同所导致的,而生态位重叠度较低情况的出现主要是由于各物种占据潮间带上不同的潮区,减小了种间竞争的压力。

Intertidal zone of the Nanji Islands is a niche for dominant species of the macrobenthic community

Since 1917, when Grinnell proposed that niche breadth is the minimum unit of a population, the theory of ecological niches has persisted as one of the core ideas in the study of community composition and function, the relationships among various species, biodiversity, community, and population evolution. Ecologists use the term "ecological niche" to describe how organisms respond to, and in turn alter, the distribution of their resources and competitors. The metrics of niche overlap, breadth, and position play a central role in our understanding of an organismal community. The Nanji Archipelago Marine Nature Reserve is located in the southeast region of Zhejiang Province, China. It is a marine ecosystem reserve, aimed at protecting marine biodiversity. Specifically, the shellfish, algae, and the natural environment are the main targets for protection. To examine the characteristics of the macrobenthic community as well as the interactions between the macrobenthic species in the rocky intertidal zone of the Nanji Islands, organism assemblages in 4 sections of the Nanji Islands were investigated between May 2012 and February 2013. During the 10 months of research, 354 species were found, most of which were molluscs, annelids, and arthropods. In addition, dominance coefficient analysis identified 18 dominant species belonging to 3 different phyla, 5 classes, and 12 families. Every tidal zone in each season was treated as a resource state, and 12 such resource states were selected for further ecological niche analysis. Indices of the niche breadth, niche overlap, and niche proportional similarity were calculated based on the abundance of the dominant species. The values of the niche breadth indices for Modiolus comptus, Septifer virgatus, and Nereis heterocirrata were the highest(greater than 0.9), while those of Euraphia withersi and Fistulobalanus albicostatus were the lowest(lower than 0.5). The values of for the niche overlap index of the macrobenthic community in the Nanji Islands were low. In contrast, the values of its niche proportional similarity were relatively high. The species with broad niche breadth were found to have high niche overlap index values and niche proportional similarity. According to the results of the Bray-Curtis similarity analysis and non-metric multidimensional scaling analysis(NMDS), there was no significant difference in community composition among the different areas in the Nanji Islands. There was only one weak distinguishing feature within community that divided the community into two groups, one group comprising of species living in the high tidal zone and the upper level of the middle tidal zone, and the other comprising species living in the low tidal zone and the lower level of the middle tidal zone. Thus, we can speculate that the different distribution patterns of the benthic species in the intertidal zones were caused by various factors involved in their environmental adaptability and migration capability. Our results also indicate that the differential environmental adaptability and migration capability of the macrobenthic species may lead to differences in their niche breadth. Since each species assumes its own position in the intertidal zone, the pressure due to inter-specific competition is reduced to some extent, possibly explaining why the niche overlap indices in the Nanji Islands were relatively low.