| 1. |
- Li, Zhonghu, et al.
(författare)
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Population Genetic Evidence for Complex Evolutionary Histories of Four High Altitude Juniper Species in the Qinghai-Tibetan Plateau
- 2012
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 66:3, s. 831-845
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Tidskriftsartikel (refereegranskat)abstract
- Population genetics data based on multiple nuclear loci provide invaluable information to understand demographic, selective, and divergence histories of the current species. We studied nucleotide variation at 13 nuclear loci in 53 populations distributed among four closely related, but morphologically distinct juniper species of the QinghaiTibetan Plateau (QTP). We used a novel approach combining Approximate Bayesian Computation and a recently developed neutrality test based on the maximum frequency of derived mutations to examine the demographic and selective histories of individual species, and isolation-with-migration analyses to study the joint history of the species and detect gene flow between them. We found that (1) the four species, which diverged in response to the extensive QTP uplifts, have different demographic histories; (2) two loci, Pgi and CC0822, depart significantly from neutrality in one species and Pgi, is also marginally significant in another; and (3) shared polymorphisms are common, indicating both incomplete lineage sorting and gene flow after species divergence. In addition, the detected unidirectional gene flow provides indirect support for the theoretical prediction that introgression should mostly take place from local to invading species. Our results, together with previous studies, underscore complex evolutionary histories of plant diversification in the biodiversity-hotspot QTP.
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| 2. |
- Huang, M. -Q, et al.
(författare)
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Switchable Copper-Catalyzed Approach to Benzodithiole, Benzothiaselenole, and Dibenzodithiocine Skeletons
- 2020
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 22:9, s. 3454-3459
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Tidskriftsartikel (refereegranskat)abstract
- A copper-catalyzed reaction between 2-bromo-benzothioamides and S8 or Se involving sulfur rearrangement is reported, enabling access to benzodithioles 2 and benzothiaselenoles 6 in the presence of Cs2CO3. In the absence of S8 or Se, the reaction affords dibenzodithiocines 7 via two consecutive C(sp2)-S Ullmann couplings.
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| 3. |
- Li, Jianquan, et al.
(författare)
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Can Language Models Make Fun? A Case Study in Chinese Comical Crosstalk
- 2023
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Ingår i: Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers). - Stroudsburg, PA : Association for Computational Linguistics. - 9781959429722 ; , s. 7581-7596
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Konferensbidrag (refereegranskat)abstract
- Language is the principal tool for human communication, in which humor is one of the most attractive parts. Producing natural language like humans using computers, a.k.a, Natural Language Generation (NLG), has been widely used for dialogue systems, chatbots, text summarization, as well as AI-Generated Content (AIGC), e.g., idea generation, and scriptwriting. However, the humor aspect of natural language is relatively under-investigated, especially in the age of pre-trained language models. In this work, we aim to preliminarily test whether NLG can generate humor as humans do. We build the largest dataset consisting of numerous Chinese Comical Crosstalk scripts (called C3 in short), which is for a popular Chinese performing art called 'Xiangsheng' or '相声' since 1800s. We benchmark various generation approaches including training-from-scratch Seq2seq, fine-tuned middle-scale PLMs, and large-scale PLMs with and without fine-tuning. Moreover, we also conduct a human assessment, showing that 1) large-scale pretraining largely improves crosstalk generation quality; and 2) even the scripts generated from the best PLM is far from what we expect. We conclude humor generation could be largely improved using large-scale PLMs, but it is still in its infancy. The data and benchmarking code are publicly available in https://github.com/anonNo2/crosstalk-generation. © 2023 Association for Computational Linguistics.
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| 4. |
- Li, Yuan, et al.
(författare)
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Demographic histories of four spruce (Picea) species of the Qinghai-Tibetan Plateau and neighboring areas inferred from multiple nuclear loci
- 2010
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Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 27:5, s. 1001-1014
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Tidskriftsartikel (refereegranskat)abstract
- Nucleotide variation at 12 to 16 nuclear loci was studied in three spruce species from the Qinghai-Tibetan Plateau (QTP), Picea likiangensis, P. wilsonii and P. purpurea, and one species from the Tian Shan mountain range, P. schrenkiana. Silent nucleotide diversity was limited in P. schrenkiana and high in the three species from the QTP, with values higher than in boreal spruce species, despite their much more restricted distributions compared to that of the boreal species. In contrast to European boreal species that have experienced severe bottlenecks in the past, coalescent-based analysis suggests that DNA polymorphism in the species from the QTP and adjacent areas is compatible with the standard neutral model (P. likiangensis, P. wilsonii, P. schrenkiana) or with population growth (P. purpurea). In order to test if P. purpurea is a diploid hybrid of P. likiangensis and P. wilsonii, we used a combination of approaches, including model based inference of population structure, Isolation-with-Migration models and recent theoretical results on the effect of introgression on the geographic distribution of diversity. In contrast to the three other species, each of which was predominantly assigned to a single cluster in the Structure analysis, P. purpurea individuals were scattered over the three main clusters and not, as we had expected, confined to the P. likiangensis and P. wilsonii clusters. Furthermore the contribution of P. schrenkiana was by far the largest one. In agreement with this, the divergence between P. purpurea and P. schrenkiana was lower than the divergence of either P. likiangensis or P. wilsonii from P. schrenkiana. These results, together with previous ones showing that P. purpurea and P. wilsonii share the same haplotypes at both chloroplast and mitochondrial markers, suggest that P. purpurea has a complex origin, possibly involving additional species.
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| 5. |
- Li, Zhonghu, et al.
(författare)
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The Pleistocene demography of an alpine juniper of the Qinghai-Tibetan Plateau : tabula rasa, cryptic refugia or something else?
- 2011
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Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 38:1, s. 31-43
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Tidskriftsartikel (refereegranskat)abstract
- Aim Numerous palaeoecological and genetic studies have shown that different tree species responded in very different ways to Pleistocene climatic oscillations. Some were forced into small refugia far from their current range, while others were able to survive in small refugia close to, or even within, their current natural range. In this study we examine the Pleistocene demography of a juniper species (Juniperus przewalskii, Cupressaceae) from the Qinghai-Tibetan Plateau. Location The Qinghai-Tibetan Plateau (QTP). Methods Eight nuclear loci were sequenced in 141 individuals from 20 natural populations distributed across the entire natural range of J. przewalskii, and coalescent analysis was used to test demographic hypotheses. Results The overall nucleotide diversity in the sample was low (pi(sil) = 0.0029), with few rare alleles and pronounced population genetic structure (F-ST = 0.181). We detected a division previously found using chloroplast DNA markers: all segregating sites in populations from the central part of the QTP appear to be a subset of those found around the edge of the plateau, confirming the relatively young age of the former. In contrast to the middle Pleistocene bottlenecks detected in boreal tree species, the coalescent-based analyses failed to reject the standard neutral model for the juniper species considered here. Main conclusions Juniperus przewalskii did not undergo marked changes in population sizes during the Pleistocene, although this species seems to have experienced recent, post-glacial expansion. This finding is largely consistent with the limited number of previous studies on conifer species of the QTP, but contradicts findings of studies on boreal species. These findings have wide implications for understanding plant species' responses to past climatic oscillations on the high-elevation QTP.
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| 6. |
- Ma, Tao, et al.
(författare)
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Genomic insights into salt adaptation in a desert poplar
- 2013
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 2797-
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Tidskriftsartikel (refereegranskat)abstract
- Despite the high economic and ecological importance of forests, our knowledge of the genomic evolution of trees under salt stress remains very limited. Here we report the genome sequence of the desert poplar, Populus euphratica, which exhibits high tolerance to salt stress. Its genome is very similar and collinear to that of the closely related mesophytic congener, P. trichocarpa. However, we find that several gene families likely to be involved in tolerance to salt stress contain significantly more gene copies within the P. euphratica lineage. Furthermore, genes showing evidence of positive selection are significantly enriched in functional categories related to salt stress. Some of these genes, and others within the same categories, are significantly upregulated under salt stress relative to their expression in another salt-sensitive poplar. Our results provide an important background for understanding tree adaptation to salt stress and facilitating the genetic improvement of cultivated poplars for saline soils.
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| 7. |
- Miehe, Georg, et al.
(författare)
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The Kobresia pygmaea ecosystem of the Tibetan highlands – Origin, functioning and degradation of the world's largest pastoral alpine ecosystem: Kobresia pastures of Tibet
- 2019
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697. ; 648, s. 754-771
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Tidskriftsartikel (refereegranskat)abstract
- With 450,000 km2 Kobresia (syn. Carex) pygmaea dominated pastures in the eastern Tibetan highlands are the world's largest pastoral alpine ecosystem forming a durable turf cover at 3000–6000 m a.s.l. Kobresia's resilience and competitiveness is based on dwarf habit, predominantly below-ground allocation of photo assimilates, mixture of seed production and clonal growth, and high genetic diversity. Kobresia growth is co-limited by livestock-mediated nutrient withdrawal and, in the drier parts of the plateau, low rainfall during the short and cold growing season. Overstocking has caused pasture degradation and soil deterioration over most parts of the Tibetan highlands and is the basis for this man-made ecosystem. Natural autocyclic processes of turf destruction and soil erosion are initiated through polygonal turf cover cracking, and accelerated by soil-dwelling endemic small mammals in the absence of predators. The major consequences of vegetation cover deterioration include the release of large amounts of C, earlier diurnal formation of clouds, and decreased surface temperatures. These effects decrease the recovery potential of Kobresia pastures and make them more vulnerable to anthropogenic pressure and climate change. Traditional migratory rangeland management was sustainable over millennia, and possibly still offers the best strategy to conserve and possibly increase C stocks in the Kobresia turf.
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| 8. |
- Wu, H., et al.
(författare)
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Modular synthesis of 3-substituted isocoumarinsviasilver-catalyzed aerobic oxidation/6-endoheterocyclization ofortho-alkynylbenzaldehydes
- 2021
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Ingår i: Organic and biomolecular chemistry. - : Royal Society of Chemistry (RSC). - 1477-0520 .- 1477-0539. ; 19:30, s. 6657-6664
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Tidskriftsartikel (refereegranskat)abstract
- A method involving silver-catalyzed aerobic oxidation/6-endoheterocyclization ofortho-alkynylbenzaldehydes to yield 3-substituted isocoumarins is described. The developed protocol allows convenient access to a range of synthetically useful 3-substituted isocoumarins and related fused heterocyclolactones in good to high yields, using silver tetrafluoroborate as the catalyst, and atmospheric oxygen as the terminal oxidant and the source of endocyclic oxygen. Mechanistic studies suggest the involvement of a free-radical pathway.
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