西沙和中沙群岛海域生物多样性特点

根据西沙和中沙群岛海域鱼类调查研究的历史资料,对鱼类物种组成进行了系统整理,发现该海域记录的鱼类种类有620种,隶属于26目98科301属。地理分布以印度-太平洋、印度-西太平洋、西太平洋3种类型为主,典型珊瑚礁鱼类的科属类型突出,证实了该水域高生物多样性、丰富生物量以及高生产力的特性。采用分类阶元包含指数分析得出,西沙和中沙群岛海域鱼类组成目、科、属所分别拥有的(科、属、种),(属、种)和(种)的平均数目分别为(3.77、11.58、23.85),(3.07、6.33)和(2.06),与东沙群岛海域较为接近,且明显高于东海陆架区海域,证明低纬度海域的鱼类分类多样性低,种类组成主要集中分布于较少数的分类类群。使用PRIMER5.2软件计算了平均分类差异指数△+和分类差异变异指数∧+,数值分别为60.0和164.0,其中△+低于东海陆架区(65.7),高于东沙群岛海域(55.2),说明西沙和中沙群岛海域鱼类组成之间的亲缘关系比东海陆架海区近而比东沙群岛海区远,这可能与西沙和中沙群岛海域主要受南海反气旋式环流系统所支配,环境因子变化大有关。对比我国同处于海洋生物物种多样性最高的印度尼西亚-马来西亚-菲律宾海区的东沙群岛和南沙群岛海域,并对10科典型的珊瑚礁鱼类进行相对丰富度和相似性指数分析,发现任意两海域之间典型珊瑚礁鱼类科的相对丰富度差异均不显著,这可能是由于他们同处西太平洋地区物种多样性中心,起源同源有关。西沙和中沙群岛与南沙群岛珊瑚礁海域较为相似,基本体现了距离越远,相似性系数越小的特点;其鱼类组成的多样性符合以世界物种多样性高的三角区为中心,呈降低的梯度分布的特点。研究结果支持西沙和中沙群岛海域鱼类地理位置靠近世界物种多样性高的三角区。

The characteristics of biodiversity of fish in Xisha & Zhongsha Islands

Based on the records of fish species in Xisha & Zhongsha Islands, we sorted out the composition of fish species systematically and found that 602 species in Xisha & Zhongsha Islands belong to 26 orders, 98 families and 301 genera, mainly distributing in Indo-Pacific,Indo-western Pacific and Western Pacific, which indicated the high biodiversity, biomass and productivity of these areas. Analyzed by the inclusion index in taxonomic level, the average number of(families, genera, species),(genera, species)and (species)in per order, family and genus were(3.77,11.58,23.85),(3.07,6.33)and(2.06), similar to the case of Dongsha Islands and obviously higher than that in the East China Sea Continent Shelf .It was showed that taxonomic diversity was lower in the lower-latitude area than in the the higher-latitude area. The average taxonomic distinctness △+ and the variation in taxonomic distinctness △+ of Xisha & Zhongsha islands(164.0)were calculated by PRIMER5.2 software. The value of △+ in the Xisha & Zhongsha Islands(60.2)was lower than that in the East China Sea Continental Shelf(65.7)but higher than that in the Dongsha Islands(55.2), which may due to the anticyclonic circulation in Xisha & Zhongsha Islands. Compared with Dongsha Islands and Nansha Islands in China and Indonesia-Malaysia-Philippines sea areas, we also analyzed the richness of 10 families and found no significant difference among them, which may be related to their locations near the triangle center where had the highest species diversity in the Westem Pacific.The similarities between Xisha & Zhongsha Islands and the NanSha Islands was closer, demonstrating that the similarity was lower with farther distance. The species diversity was gradiently distributed since the triangle center where had the highest species diversity in the world.The results of the paper supported the inference that the fish species diversity was appropriate higher in Xisha & Zhongsha Islands since it was near the triangle center.