秦岭细鳞鲑栖息地环境特征研究

为研究秦岭细鳞鲑（Brachymystax lenok tsinlingensis）的栖息地环境选择偏好，对陕西陇县秦岭细鳞鲑国家级自然保护区和甘肃秦州珍稀水生野生动物国家级自然保护区内25个样点进行了鱼类采样和生境测量。共采集到130尾秦岭细鳞鲑样本，样点的平均分布密度为（0.10±0.07）尾/m，两个保护区内秦岭细鳞鲑的密度存在显著性差异（P < 0.05）。与秦岭细鳞鲑密度分布呈正相关的因子依次为坡度、跌水区密度、海拔、粗糙度、遮蔽度、底栖动物生物量和流速，与密度呈负相关的环境因子依次为河宽、水深和溶氧。冗余性分析（RDA）筛选了坡度、粗糙度、遮蔽度、海拔和跌水区5个关键环境因子。基于关键环境因子的实测值建立了栖息地适合度曲线，秦岭细鳞鲑分布的最适坡度范围为5%-10%，海拔分布范围为1500-2000 m，粗糙度范围0.3-0.4；跌水区密度范围12-18个/100 m，遮蔽度在0.5以上。     

RETRACTED ARTICLE: An analysis of population structure and linkage disequilibrium using multilocus data in 187 maize inbred lines

This study analyzes population structure and linkage disequilibrium (LD) among 187 commonly used Chinese maize inbred lines, representing the genetic diversity among public, commercial and historically important lines for corn breeding. Seventy SSR loci, evenly distributed over 10 chromosomes, were assayed for polymorphism. The identified 290 alleles served to estimate population structure and analyze the genome-wide LD. The population of lines was highly structured, showing 6 subpopulations: BSSS (American BSSS including Reid), PA (group A germplasm derived from modern U.S. hybrids in China), PB (group B germplasm derived from modern U.S. hybrid in China), Lan (Lancaster Surecrop), LRC (derivative lines from Lvda Reb Cob, a Chinese landrace) and SPT (derivative lines from Si-ping-tou, a Chinese landrace). Forty lines, which formerly had an unknown and/or miscellaneous origin and pedigree record, were assigned to the appropriate group. Relationship estimates based on SSR marker data were quantified in a Q matrix, and this information will inform breeder’s decisions regarding crosses. Extensive inter- and intra-chromosomal LD was detected between 70 microsatellite loci for the investigated maize lines (2109 loci pairs in LD with D′ > 0.1 and 93 out of them at P < 0.01).This suggests that rapidly evolving microsatellites may track recent population structure. Interlocus LD decay among the diverse maize germplasm indicated that association studies in QTLs and/or candidate genes might avoid nonfunctional and spurious associations since most of the LD blocks were broken between diverse germplasm. The defined population structure and the LD analysis present the basis for future association mapping. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Three‐Stage Inter‐Orthorhombic Evolution and High Thermoelectric Performance in Ag‐Doped Nanolaminar SnSe Polycrystals

The ultrahigh thermoelectric performance of SnSe‐based single crystals has attracted considerable interest in their polycrystalline counterparts. However, the temperature‐dependent structural transition in SnSe‐based thermoelectric materials and its relationship with their thermoelectric performance are not fully investigated and understood. In this work, nanolaminar SnSe polycrystals are prepared and characterized in situ using neutron and synchrotron powder diffraction measurements at various temperatures. Rietveld refinement results indicate that there is a complete inter‐orthorhombic evolution from Pnma to Cmcm by a series of layer slips and stretches along the a‐ and b‐axes over a 200 K temperature range. This phase transition leads to drastic enhancement of the carrier concentration and phonon scattering above 600 K. Moreover, the unique nanolaminar structure effectively enhances the carrier mobility of SnSe. Their grain and layer boundaries further improve the phonon scattering. These favorable factors result in a high ZT of 1.0 at 773 K for pristine SnSe polycrystals. The thermoelectric performances of polycrystalline SnSe are further improved by p‐type and n‐type dopants (i.e., doped with Ag and SnCl₂, respectively), and new records of ZT are achieved in Ag_0.015Sn_0.985Se (ZT of 1.3 at 773 K) and SnSe_0.985Cl_0.015 (ZT of 1.1 at 773 K) polycrystals.