Microsatellite DNA and clonal structure in the sea whip, Junceella juncea (Octocorallia: Gorgonacea)

• Main Authors: Shang-Yin Liu, 劉商隱
• Other Authors: Chang-Feng Dai
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/79907657462118877409

碩士 === 國立臺灣大學 === 海洋研究所 === 91 === Abstract The identification of different clones is fundamental to the study of population structure among asexual populations. However, due to the low genetic variation of mtDNA and the contamination of zooxanthellate DNA, very few molecular markers are available for studying the clonal structure of cnidarians. The highly variant tandem repeats (microsatellite DNA) randomly distributed among the eukaryote genomes are useful markers to study clonal structure of colonial cnidarians. In this study, we isolated 6 loci from a zooxanthellae-free octocoral Junceella juncea using methods of enrichment and traditional partial library screening. Among the 3856 clones screened by partial library method, only 10 positive signals were found and 3 of them could be used to design primers and be well amplified. However, all loci isolated by enrichment method showed low variations or were monomorphic among populations, it may result in in vitro hybridization during PCR amplification. Overall, 4 of 6 loci were polymorphic and the other 2 were monomorphic. We used the 4 polymorphic loci to study the clonal structure of J. juncea collected from 7 reefs at 3 sites, i.e. Xia-shui-jui, Nanwan in southern Taiwan, and Shi-cheng in northern Taiwan. A total of 40 multilocus genotypes were found among 152 colonies and the number of genotypes (clones) identified at 7 reefs ranged from 2 to 16. The ratio of observed to expected genotypic diversity (Go:Ge) ranged from 0.018 to 0.422 suggesting that asexual reproduction plays a major role in the maintenance of established populations. The results also indicate that the distribution of microsatellites may be rare in Junceella juncea’s genome and the high variation of microsatellites can be used to identify the genets and remets within populations. The feasibility of using microsatellites to estimate genetic variations among populations was discussed.