Phylogenomics reveal Populusgonggaensis as a hybrid between P.lasiocarpa and P.cathayana (Salicaceae).

High levels of intra-specific polymorphism and frequent hybridisation make it difficult to define species and correctly apply their scientific names. Populus L. is a challenging genus with plentiful natural and artificial hybrids. This study is a part of the project 'Flora of Pan-Himalaya' and aims to determine the taxonomic identity of P.gonggaensis N. Chao & J.R. He and to find out whether it is of hybrid origin. Whole-genome sequencing data were obtained from 57 samples. The SNP matrix was developed for phylogenetic reconstruction, ABBA-BABA statistics, PCA and ADMIXTURE analysis. The results indicate that P.gonggaensis is a spontaneous hybrid between P.lasiocarpa and P.cathayana. This study points out the importance of SNP data and comprehensive analyses for discovering the potential interspecific hybridisation and clarifies the usage of the name. In addition, the lectotype of P.gonggaensis was designated.

Paraboeazunyiensis (Gesneriaceae), a new species from north Guizhou, China.

A new lithophytic species, Paraboeazunyiensis T.Deng, F.Wen & R.B.Zhang (Gesneriaceae), inhabiting Karst rocks in northern Guizhou, China, is introduced and depicted in this study. It bears a resemblance to P.crassifolia (Hemsl.) B.L. Burtt, yet is distinguishable by its shorter filaments and staminodes, triangular ovate calyx segments, and ovaries surpassing the styles in length. Moreover, the phylogenetic tree constructed from nuclear DNA (ITS) and plastid DNA (trnL-F) data firmly support the differentiation of this novel species from P.crassifolia.

Experimental and theoretical study on molecular aggregation and its effect on the photo-physical properties of the mesogenic bi-1,3,4-thiadiazole derivative.

A bi-thiadiazole derivative, 5,5'-bis(4- tetradecyloxyphenyl)-2,2'-bi-1,3,4-thiadiazole (BTD-14), was revealed to exhibit an extremely stable thermotropic SmC phase and very interesting aggregation behavior in solutions. H- and J-aggregates could be formed simultaneously in chloroform solutions of BTD-14 with moderate concentration (10(-4) M), and the population of J-aggregates enlarges during further concentration increase. All monomers, H-aggregates and J-aggregates in solutions could be reserved in the drop-cast films, and both the presence of J-aggregates and the energy transfer path from H-aggregates to J-aggregates were considered to contribute to the relative high solid state fluorescence quantum yield (33%). The BTD-1 dimer potential energy surface (PES) was computed with M062x/6-31G** method, and the molecular packing pattern corresponding to the lowest minimum of the PES are in good agreement with the crystal structures. Exploring the effect of molecular packing on its electronic structure with the TD-M062x method revealed that J-aggregates could be formed by enlarging the intermolecular displacement along the molecular long axis by about 9.8 Å.