Population connectivity of Pomacentrus coelestis in Northern West-Pacific
Date Issued
2008
Date
2008
Author(s)
Liu, Shang-Yin Vanson
Abstract
Analysis of genetic data can reveal past and ongoing connectivity among reef fish populations, and using geochemical signatures in calcified structures provide another indirect means of tracing movements and determining the population origin of reef fishes. These methods can be applied to determine which populations are connected by larval transport, and the results of these studies are crucial for effective management of fisheries and the design of marine reserves. In this dissertation, I used both methods to study the connectivity of Pomacentrus coelestis among populations in the West-Pacific. he results of genetic analysis indicated that a genetic break existed between mainland Japan and Okinawa populations, and this break was congruent with the pattern of phenotypic variations documented in previous studies. This evidence supports that the latitudinal variation of reproductive traits among P. coelestis populations is likely being genetically based. The historical demography of P. coelestis revealed by molecular data suggested that drastic changes in sea level and sea surface temperatures during the last glaciations might have resulted in dramatic reduction of their population size in the northwestern Pacific. Among populations around Taiwan, a genetic break was found between the Penghu-northern Taiwan group and the southern Taiwan group (Kenting and Hainan populations). However, the results of Bayesian assignments revealed a larval transportation pattern differed from that proposed by previous studies. The recruits in southern Taiwan were mainly from the South China Sea (approximately 50%), while the recruits in Penghu and northern Taiwan were from mixed sources. Moreover, both Φst of adult populations and Fst of recruit populations indicated limited gene flow between Penghu-northern Taiwan and southern Taiwan groups. It suggests that the recruits in southern Taiwan may have different origins comparing with those of northern Taiwan and Penghu populations.he geochemical signatures in sagittae showed that significant differences were found in Mg/Ca, Mn/Ca, Sr/Ca, Ba/Ca and δ18O values among sites in pre-settlement region of otoliths. By using the combined data of trace element ratios and stable isotopic compositions, the results of PCA (principal component analysis) showed that the otoliths collected from Tiaoshi, southern Taiwan and other three sites (Maoao, Yehliu and Chinwan Outer Bay) around Taiwan could be separated. This indicates that the population at Tiaoshi may have different source which is congruent with the results of genetic studies. Overall, it suggests P. coelestis larvae may be transported by the South China Sea Surface Water (SCSSW) from Hainan Island to southern Taiwan, and the population at Chinwan Outer Bay in Penghu and Yehliu in northern Taiwan may share the same gene pool (Fst = -0.0001, p > 0.05). In addition, the results also indicated that the incorporation of Ba/Ca and Mn/Ca element ratios in P. coelestis otolith could control by physiological regulations. Thus, caution is warranted when using these two element ratios. hese results suggest that the last glaciations had profound effect on the historical demography of P. coelestis, and the recent demographic connectivity was mainly determined by local hydrodynamic regimes. Since self retention is unlikely the case in P. coelestis populations, the connectivity patterns of P. coelestis could be used as a reference for designing effective management strategies on marine organisms with low degree of self retention in the West-Pacific.
Subjects
Pomacentrus coelestis
population connectivity
microsatellite
otolith chemistry
historical demography
West Pacific
SDGs
Type
thesis
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