关键词: 裸体方格星虫, 线粒体COI基因, 遗传多样性, 隐蔽种, Sipunculus nudus, mtDNA COI, genetic diversity, cryptic species

Abstract: Genetic structure and population differentiation in wild populations of Sipunculus nudus were researched in this paper. 91samples collected from Changle、Gulei、Jinjiang in Fujian province and 15 from Xiamen、Beihai、Sanya were studied based on sequence analyses of the mitochondrial cytochrome oxidase I(mtDNA COI) gene segment. 193 nucleotide polymorphisms and 52 haplotypes were found in total 106 samples. Among three Fujian geographical groups, gene diversities (π) ranged from 0.00155 to 0.01325, and the nucleotide diversities (h) from 0.626 to 0.972, showed that Sipunculus nudus has high genetic diversity. AMOVA analysis disclosed that variation between populations accounting for 98.03% of total variation, revealing that variations occurred between populations were the main source of the total variation. Neighbor-joining tree based on mtDNA COI sequence showed A、B、C and D four different branches with high support value. The four distinct clades among south China coastal waters revealed underestimate cryptic diversity within Sipunculus nudus. Minimum spanning network from all haplotypes reveals two distinct branches as Fujian and the northern Gulf in groups A, which may be approached to subspecies level upon further research. This study may be useful for the resources protection, artificial seed stocking and genetic breeding of Sipunculus nudus．