Evaluation of spatial-temporal variability of species composition and diversity in oceanic ecosystems is not easy because it is usually difficult to obtain sufficient data quantifying such variability.In this study,we...Evaluation of spatial-temporal variability of species composition and diversity in oceanic ecosystems is not easy because it is usually difficult to obtain sufficient data quantifying such variability.In this study,we examined pelagic species diversity indicators,species richness,Shannon-Wiener index of diversity and Hurlbert's species evenness,for fish assemblages from two areas(north and south) in the North Pacific Ocean(2°±12°N,178°E±165°W) during May±July 2008.The assemblages were based on data collected by an onboard scientific observer during a commercial longline fishing trip.The species richness and Shannon-Wiener diversity index of fish assemblages in the northern area were slightly higher than those in the southern area,although these differences were not significant(t test,P.0.05).Non-parametric multidimensional scaling and analysis of similarities indicated that there were significant differences in fish assemblages between the two areas(P,0.01).展开更多
Genus Nassarius contains many subgenera, such as Zeuxis, Telasco, Niotha, Varicinassa, Plicarcularia, Nassarius s. str. and Reticunassa. On the basis of morphological characteristics of the shell and radula and sequen...Genus Nassarius contains many subgenera, such as Zeuxis, Telasco, Niotha, Varicinassa, Plicarcularia, Nassarius s. str. and Reticunassa. On the basis of morphological characteristics of the shell and radula and sequences of mitochondrial cytochrome oxidase subunit I (COI) and 16S rRNA genes, Nassarius specimens collected from the South China Sea were identified and phylogenetically analyzed. Although Nassarius sp. and Nassarius (Varicinassa) variciferus were morphologically different in their shells, few variations were found among their radular teeth and sequences of mtCOI and mt16S RNA genes. Therefore, Nassarius sp. should be classified as N. (Varicinassa) variciferus. Nassarius (Zeuxis) sp. has only a subtle difference from Nassarius (Zeuxis) algidus on the shell, but it shows obvious differences in radular teeth and DNA sequence, indicating that they are two distinct species. Sequence divergence of mtCOI and mt16S RNA genes within Nassarius species was much lower than that between species, suggesting that these two genes are suitable for Nassarius species identification. Phylogenetic analysis (neighbor-joining and maximum parsimony) based on mtCOI and mt16S rRNA genes revealed the presence of two groups in genus Nassarius and a closest relationship between subgenera Zeuxis and Telasco. Species of subgenus Plicarcularia did not form a single clade. The molecular phylogeny was not congruent with the previous morphological phylogeny. The subgeneric divisions of genus Nassarius appear to be uncertain and unreliable.展开更多
To facilitate the development of the basis for the selection of plants for re-vegetating tailings in Zambia, an as sessment of the performance of tree species growing on tailings dams was conducted. The performance of...To facilitate the development of the basis for the selection of plants for re-vegetating tailings in Zambia, an as sessment of the performance of tree species growing on tailings dams was conducted. The performance of species was determined in terms of relative density, frequency and importance value for each species. The study reveals variations in performance of species; for example in terms of importance values, Acacia polyacantha （33.5%）, Toona ciliata （21.4%）, Acacia sieberana （9.9%）, Bauhinia thonningii （9.1%） and Peltophorum africanum （8.3%） were the most dominant species. The dominance of these species on tailings dams demonstrates tolerance to railings dams conditions. The study recommends that emphasis must be placed on these species in re-vegetating tailings dams.展开更多
Tea plant is cross pollinated plant, it forms a variety of the tea Germplasm constantly in the long-term breeding process. Tea Germplasm resources are the material foundation for improving varieties and also the basic...Tea plant is cross pollinated plant, it forms a variety of the tea Germplasm constantly in the long-term breeding process. Tea Germplasm resources are the material foundation for improving varieties and also the basic research which is good for developing and expanding tea well-bred varieties in tea field, especially in quality selection and biotechnology research. Furthermore, excellent tea germplasm is primary condition for tea breeding and quality. Therefore, identification and screening excellent tea germplasm become particularly important. We need accelerate develop high-quality tea varieties, and it need to base on exploring and studying tea germplasm. This paper reviews the research progress of tea germplasm on identification from morphological characteristic, biological characteristic, quality characteristic, resistance and heredity. However, there are still some problems on identification and screening of tea germplasm, no effective methods have been found so far which apply on early identification and genetic engineering, so we should make intensive and long lasting study tea germplasm and analyze systematically various identification, which are benefit for breeding high-quality seeds, shortening the breeding period and summing the new way of breeding. We expect them to play the key roles and provide the theory basis for genetic improvement, classification and breeding in tea plant.展开更多
Bitter taste reception is presumably associated with dietary selection, preventing animals from ingesting potentially harmful compounds. Accordingly, carnivores, who encounter these toxic substances less often, should...Bitter taste reception is presumably associated with dietary selection, preventing animals from ingesting potentially harmful compounds. Accordingly, carnivores, who encounter these toxic substances less often, should have fewer genes associated with bitter taste reception compared with herbivores and omnivores. To investigate the genetic basis of bitter taste reception, we confirmed bitter taste receptor （T2R） genes previously found in the genome sequences of two herbivores （cow and horse）, two omnivores （mouse and rat） and one carnivore （dog）. We also identified, for the first time, the T2R repertoire from the genome of other four carnivore species （ferret, giant panda, polar bear and cat） and detected 17-20 bitter receptor genes from the five carnivore genomes, including 12-16 intact genes, 0-1 partial but putatively functional genes, and 3-8 pseudogenes. Both the intact T2R genes and the total T2R gene number among carnivores were the smallest among the tested species, supporting earlier speculations that carnivores have fewer T2R genes, herbivores an intermediate number, and onmivores the largest T2R gene repertoire. To further explain the genetic basis for this disparity, we constructed a phylogenetic tree, which showed most of the T2R genes from the five carnivores were one-to-one orthologs across the tree, suggesting that carnivore T2Rs were conserved among mammals. Similarly, the small carnivore T2R family size was likely due to rare duplication events. Collectively, these results strengthen arguments for the connection between T2R gene family size, diet and habit.展开更多
A growing number of genes responsible for reproductive incompatibilities between species （barrier loci） exhibit the signals of positive selection. However, the possibility that genes experiencing positive selection ...A growing number of genes responsible for reproductive incompatibilities between species （barrier loci） exhibit the signals of positive selection. However, the possibility that genes experiencing positive selection diverge early in speciation and commonly cause reproductive incompatibilities has not been systematically investigated on a genome-wide scale. Here, I outline a research program for studying the genetic basis of speciation in broadcast spawning marine invertebrates that uses a priori genome-wide information on a large, unbiased sample of genes tested for positive selection. A targeted sequence capture approach is proposed that scores single-nucleotide polymorphisms （SNPs） in widely separated species populations at an early stage of allopatric divergence. The targeted capture of both coding and non-coding sequences enables SNPs to be characterized at known locations across the genome and at genes with known selective or neutral histories. The neutral coding and non-coding SNPs provide robust background distributions for identifying Fsm-outliers within genes that can, in principle, identify specific mutations experiencing diversifying selection. If natural hybridization occurs between species, the neutral coding and noncoding SNPs can provide a neutral admixture model for genomic clines analyses aimed at finding genes exhibiting strong blocks to introgression. Strongylocentrotid sea urchins are used as a model system to outline the approach but it can be used for any group that has a complete reference genome available.展开更多
Reinforcement--the process whereby maladaptive hybridization leads to the strengthening of prezygotic isolation between species--has a long history in the study of speciation. Because reinforcement affects traits invo...Reinforcement--the process whereby maladaptive hybridization leads to the strengthening of prezygotic isolation between species--has a long history in the study of speciation. Because reinforcement affects traits involved in mate choice and fertility, it can have indirect effects on reproductive isolation between populations within species. Here we review examples of these ＂cascading effects of reinforcement＂ （CER） and discuss different mechanisms through which they can arise. We discuss three factors that are predicted to influence the potential occurrence of CER： rates of gene flow among populations, the strength of selection acting on the traits involved in reinforcement, and the genetic basis of those traits. We suggest that CER is likely if （1） the rate of gene flow between conspecific populations is low; （2） divergent selection acts on phenotypes involved in reinforcement between sympatric and allopatric populations; and （3） the genetic response to reinforcement differs among conspecific populations subject to parallel reinforcing selection. Future work continuing to address gene flow, selection, and the genetic basis of the traits involved in the reinforcement will help develop a better understanding of reinforcement as a process driving the production of species diversity, both directly and incidentally.展开更多
The relationship between crop richness and predator-prey interactions as they relate to pest-natural enemy systems is a very important topic in ecology and greatly affects biological control services.The effects of cr...The relationship between crop richness and predator-prey interactions as they relate to pest-natural enemy systems is a very important topic in ecology and greatly affects biological control services.The effects of crop arrangement on predator-prey interactions have received much attention as the basis for pest population management.To explore the internal mechanisms and factors driving the relationship between crop richness and pest population management,we designed an experimental model system of a microlandscape that included 50 plots and five treatments.Each treatment had 10 repetitions in each year from 2007 to 2010.The results showed that the biomass of pests and their natural enemies increased with increasing crop biomass and decreased with decreasing crop biomass;however,the effects of plant biomass on the pest and natural enemy biomass were not significant.The relationship between adjacent trophic levels was significant(such as pests and their natural enemies or crops and pests),whereas non-adjacent trophic levels(crops and natural enemies) did not significantly interact with each other.The ratio of natural enemy/pest biomass was the highest in the areas of four crop species that had the best biological control service.Having either low or high crop species richness did not enhance the pest population management service and lead to loss of biological control.Although the resource concentration hypothesis was not well supported by our results,high crop species richness could suppress the pest population,indicating that crop species richness could enhance biological control services.These results could be applied in habitat management aimed at biological control,provide the theoretical basis for agricultural landscape design,and also suggest new methods for integrated pest management.展开更多
基金Supported by the China National Fishery Observer Programthe Shanghai Leading Academic Discipline Project (No. S30702)
文摘Evaluation of spatial-temporal variability of species composition and diversity in oceanic ecosystems is not easy because it is usually difficult to obtain sufficient data quantifying such variability.In this study,we examined pelagic species diversity indicators,species richness,Shannon-Wiener index of diversity and Hurlbert's species evenness,for fish assemblages from two areas(north and south) in the North Pacific Ocean(2°±12°N,178°E±165°W) during May±July 2008.The assemblages were based on data collected by an onboard scientific observer during a commercial longline fishing trip.The species richness and Shannon-Wiener diversity index of fish assemblages in the northern area were slightly higher than those in the southern area,although these differences were not significant(t test,P.0.05).Non-parametric multidimensional scaling and analysis of similarities indicated that there were significant differences in fish assemblages between the two areas(P,0.01).
基金Supported by the Youth Science Foundation of the State Oceanic Administration (No. 2009106)the Directorate Foundation of South China Sea Branch, the State Oceanic Administration (No. 0815)
文摘Genus Nassarius contains many subgenera, such as Zeuxis, Telasco, Niotha, Varicinassa, Plicarcularia, Nassarius s. str. and Reticunassa. On the basis of morphological characteristics of the shell and radula and sequences of mitochondrial cytochrome oxidase subunit I (COI) and 16S rRNA genes, Nassarius specimens collected from the South China Sea were identified and phylogenetically analyzed. Although Nassarius sp. and Nassarius (Varicinassa) variciferus were morphologically different in their shells, few variations were found among their radular teeth and sequences of mtCOI and mt16S RNA genes. Therefore, Nassarius sp. should be classified as N. (Varicinassa) variciferus. Nassarius (Zeuxis) sp. has only a subtle difference from Nassarius (Zeuxis) algidus on the shell, but it shows obvious differences in radular teeth and DNA sequence, indicating that they are two distinct species. Sequence divergence of mtCOI and mt16S RNA genes within Nassarius species was much lower than that between species, suggesting that these two genes are suitable for Nassarius species identification. Phylogenetic analysis (neighbor-joining and maximum parsimony) based on mtCOI and mt16S rRNA genes revealed the presence of two groups in genus Nassarius and a closest relationship between subgenera Zeuxis and Telasco. Species of subgenus Plicarcularia did not form a single clade. The molecular phylogeny was not congruent with the previous morphological phylogeny. The subgeneric divisions of genus Nassarius appear to be uncertain and unreliable.
文摘To facilitate the development of the basis for the selection of plants for re-vegetating tailings in Zambia, an as sessment of the performance of tree species growing on tailings dams was conducted. The performance of species was determined in terms of relative density, frequency and importance value for each species. The study reveals variations in performance of species; for example in terms of importance values, Acacia polyacantha （33.5%）, Toona ciliata （21.4%）, Acacia sieberana （9.9%）, Bauhinia thonningii （9.1%） and Peltophorum africanum （8.3%） were the most dominant species. The dominance of these species on tailings dams demonstrates tolerance to railings dams conditions. The study recommends that emphasis must be placed on these species in re-vegetating tailings dams.
文摘Tea plant is cross pollinated plant, it forms a variety of the tea Germplasm constantly in the long-term breeding process. Tea Germplasm resources are the material foundation for improving varieties and also the basic research which is good for developing and expanding tea well-bred varieties in tea field, especially in quality selection and biotechnology research. Furthermore, excellent tea germplasm is primary condition for tea breeding and quality. Therefore, identification and screening excellent tea germplasm become particularly important. We need accelerate develop high-quality tea varieties, and it need to base on exploring and studying tea germplasm. This paper reviews the research progress of tea germplasm on identification from morphological characteristic, biological characteristic, quality characteristic, resistance and heredity. However, there are still some problems on identification and screening of tea germplasm, no effective methods have been found so far which apply on early identification and genetic engineering, so we should make intensive and long lasting study tea germplasm and analyze systematically various identification, which are benefit for breeding high-quality seeds, shortening the breeding period and summing the new way of breeding. We expect them to play the key roles and provide the theory basis for genetic improvement, classification and breeding in tea plant.
基金supported by the Key Project (30930015)General Project (31271329) from National Natural Science Foundation of China
文摘Bitter taste reception is presumably associated with dietary selection, preventing animals from ingesting potentially harmful compounds. Accordingly, carnivores, who encounter these toxic substances less often, should have fewer genes associated with bitter taste reception compared with herbivores and omnivores. To investigate the genetic basis of bitter taste reception, we confirmed bitter taste receptor （T2R） genes previously found in the genome sequences of two herbivores （cow and horse）, two omnivores （mouse and rat） and one carnivore （dog）. We also identified, for the first time, the T2R repertoire from the genome of other four carnivore species （ferret, giant panda, polar bear and cat） and detected 17-20 bitter receptor genes from the five carnivore genomes, including 12-16 intact genes, 0-1 partial but putatively functional genes, and 3-8 pseudogenes. Both the intact T2R genes and the total T2R gene number among carnivores were the smallest among the tested species, supporting earlier speculations that carnivores have fewer T2R genes, herbivores an intermediate number, and onmivores the largest T2R gene repertoire. To further explain the genetic basis for this disparity, we constructed a phylogenetic tree, which showed most of the T2R genes from the five carnivores were one-to-one orthologs across the tree, suggesting that carnivore T2Rs were conserved among mammals. Similarly, the small carnivore T2R family size was likely due to rare duplication events. Collectively, these results strengthen arguments for the connection between T2R gene family size, diet and habit.
基金Acknowledgments I would like to thank Nicolas Bierne for the opportunity of contributing to the Special Column： Population Genomics in the Sea. Helpful comments on the manuscript were provided by Nicolas Bierne and two anonymous reviewers.Partial funding for the work described on strongylocentrotid sea urchins was provided by the Natinal Science Foundation （DEB-1011061 ）.
文摘A growing number of genes responsible for reproductive incompatibilities between species （barrier loci） exhibit the signals of positive selection. However, the possibility that genes experiencing positive selection diverge early in speciation and commonly cause reproductive incompatibilities has not been systematically investigated on a genome-wide scale. Here, I outline a research program for studying the genetic basis of speciation in broadcast spawning marine invertebrates that uses a priori genome-wide information on a large, unbiased sample of genes tested for positive selection. A targeted sequence capture approach is proposed that scores single-nucleotide polymorphisms （SNPs） in widely separated species populations at an early stage of allopatric divergence. The targeted capture of both coding and non-coding sequences enables SNPs to be characterized at known locations across the genome and at genes with known selective or neutral histories. The neutral coding and non-coding SNPs provide robust background distributions for identifying Fsm-outliers within genes that can, in principle, identify specific mutations experiencing diversifying selection. If natural hybridization occurs between species, the neutral coding and noncoding SNPs can provide a neutral admixture model for genomic clines analyses aimed at finding genes exhibiting strong blocks to introgression. Strongylocentrotid sea urchins are used as a model system to outline the approach but it can be used for any group that has a complete reference genome available.
文摘Reinforcement--the process whereby maladaptive hybridization leads to the strengthening of prezygotic isolation between species--has a long history in the study of speciation. Because reinforcement affects traits involved in mate choice and fertility, it can have indirect effects on reproductive isolation between populations within species. Here we review examples of these ＂cascading effects of reinforcement＂ （CER） and discuss different mechanisms through which they can arise. We discuss three factors that are predicted to influence the potential occurrence of CER： rates of gene flow among populations, the strength of selection acting on the traits involved in reinforcement, and the genetic basis of those traits. We suggest that CER is likely if （1） the rate of gene flow between conspecific populations is low; （2） divergent selection acts on phenotypes involved in reinforcement between sympatric and allopatric populations; and （3） the genetic response to reinforcement differs among conspecific populations subject to parallel reinforcing selection. Future work continuing to address gene flow, selection, and the genetic basis of the traits involved in the reinforcement will help develop a better understanding of reinforcement as a process driving the production of species diversity, both directly and incidentally.
基金supported by the National Natural Science Foundation of China (31030012)National Key Technology Research & Development Program (2012BAD19B05)Special Fund for Agro-scientific Research in the Public Interest (201103012)
文摘The relationship between crop richness and predator-prey interactions as they relate to pest-natural enemy systems is a very important topic in ecology and greatly affects biological control services.The effects of crop arrangement on predator-prey interactions have received much attention as the basis for pest population management.To explore the internal mechanisms and factors driving the relationship between crop richness and pest population management,we designed an experimental model system of a microlandscape that included 50 plots and five treatments.Each treatment had 10 repetitions in each year from 2007 to 2010.The results showed that the biomass of pests and their natural enemies increased with increasing crop biomass and decreased with decreasing crop biomass;however,the effects of plant biomass on the pest and natural enemy biomass were not significant.The relationship between adjacent trophic levels was significant(such as pests and their natural enemies or crops and pests),whereas non-adjacent trophic levels(crops and natural enemies) did not significantly interact with each other.The ratio of natural enemy/pest biomass was the highest in the areas of four crop species that had the best biological control service.Having either low or high crop species richness did not enhance the pest population management service and lead to loss of biological control.Although the resource concentration hypothesis was not well supported by our results,high crop species richness could suppress the pest population,indicating that crop species richness could enhance biological control services.These results could be applied in habitat management aimed at biological control,provide the theoretical basis for agricultural landscape design,and also suggest new methods for integrated pest management.
