The relatively conserved 18S is often used in the phylogenetic analysis of microalgae. However, whether it can really help in barcoding microalgae needs to be evaluated. In this study the multiple approaches of coales...The relatively conserved 18S is often used in the phylogenetic analysis of microalgae. However, whether it can really help in barcoding microalgae needs to be evaluated. In this study the multiple approaches of coalescent, distance and character-based barcoding are first employed in C hlorella and Scenedesmus to test the efficiency of 18S sequences for barcoding green microalgae. We show that most Chlorella and Scenedesmus species, including the cryptic species, can be distinguished by 18S sequences with all coalescent General Mixed Yule-coalescent(GMYC), poisson tree process(PTP), and P ID, distance(ABGD) and character-based approaches. Both GMYC and PTP analyses produce more genetic groups. The P ID and ABGD analyses only cluster some species. All species(apart from a few of lineages) can be separated in character-based barcoding analysis with more than three character attributes. In comparison with previous barcoding results with r bcL, tufA, ITS and 16 S, 18S produces good resolution in identifying Chlorella and Scenedesmus. Our results reveal that 18S is highly efficient in identifying taxa of green microalgae at species level, based on a combination of multiple barcoding approaches. Combining 18S with other gene markers may be useful in barcoding microalgae.展开更多
In this study, we propose a simple linear least squares estimation method(LLS) based on a Fourier transform to estimate the complex frequency of a harmonic signal. We first use a synthetically-generated noisy time ser...In this study, we propose a simple linear least squares estimation method(LLS) based on a Fourier transform to estimate the complex frequency of a harmonic signal. We first use a synthetically-generated noisy time series to validate the accuracy and effectiveness of LLS by comparing it with the commonly used linear autoregressive method(AR). For an input frequency of 0.5 m Hz, the calculated deviations from the theoretical value were 0.004‰and 0.008‰ for the LLS and AR methods respectively; and for an input 5 10 6attenuation,the calculated deviations for the LLS and AR methods were 2.4% and 1.6%. Though the theory of the AR method is more complex than that of LLS, the results show LLS is a useful alternative method. Finally, we use LLS to estimate the complex frequencies of the five singlets of the0S2 mode of the Earth’s free oscillation. Not only are the results consistent with previous studies, the method has high estimation precisions, which may prove helpful in determining constraints on the Earth’s interior structures.展开更多
基金Supported by the China Post-doctoral Science Foundation(Nos.2014M561661,2015T80558)the Natural Science Foundation of Jiangsu Province(No.BK20150680)+1 种基金the National Natural Science Foundation of China(No.31600294)the Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization and Fundamental Research Funds for the Central Universities of Ministry of Education of China(No.Y0201600141)
文摘The relatively conserved 18S is often used in the phylogenetic analysis of microalgae. However, whether it can really help in barcoding microalgae needs to be evaluated. In this study the multiple approaches of coalescent, distance and character-based barcoding are first employed in C hlorella and Scenedesmus to test the efficiency of 18S sequences for barcoding green microalgae. We show that most Chlorella and Scenedesmus species, including the cryptic species, can be distinguished by 18S sequences with all coalescent General Mixed Yule-coalescent(GMYC), poisson tree process(PTP), and P ID, distance(ABGD) and character-based approaches. Both GMYC and PTP analyses produce more genetic groups. The P ID and ABGD analyses only cluster some species. All species(apart from a few of lineages) can be separated in character-based barcoding analysis with more than three character attributes. In comparison with previous barcoding results with r bcL, tufA, ITS and 16 S, 18S produces good resolution in identifying Chlorella and Scenedesmus. Our results reveal that 18S is highly efficient in identifying taxa of green microalgae at species level, based on a combination of multiple barcoding approaches. Combining 18S with other gene markers may be useful in barcoding microalgae.
基金supported by National 973 Project China (2013CB733302,2013CB733305)NSFCs (41174011, 41429401, 41210006, 41128003, 41021061)
文摘In this study, we propose a simple linear least squares estimation method(LLS) based on a Fourier transform to estimate the complex frequency of a harmonic signal. We first use a synthetically-generated noisy time series to validate the accuracy and effectiveness of LLS by comparing it with the commonly used linear autoregressive method(AR). For an input frequency of 0.5 m Hz, the calculated deviations from the theoretical value were 0.004‰and 0.008‰ for the LLS and AR methods respectively; and for an input 5 10 6attenuation,the calculated deviations for the LLS and AR methods were 2.4% and 1.6%. Though the theory of the AR method is more complex than that of LLS, the results show LLS is a useful alternative method. Finally, we use LLS to estimate the complex frequencies of the five singlets of the0S2 mode of the Earth’s free oscillation. Not only are the results consistent with previous studies, the method has high estimation precisions, which may prove helpful in determining constraints on the Earth’s interior structures.
