Conservation genomics provides insights into genetic resilience and adaptation of the endangered Chinese hazelnut, Corylus chinensis

Global climate change has increased concerns regarding biodiversity loss.However,many key conservation issues still required further research,including demographic history,deleterious mutation load,adaptive evolution,and putative introgression.Here we generated the first chromosome-level genome of the endangered Chinese hazelnut,Corylus chinensis,and compared the genomic signatures with its sympatric widespread C.kwechowensis-C yunnanensis complex.We found large genome rearrangements across all Corylus species and identified species-specific expanded gene families that may be involved in adaptation.Population genomics revealed that both C.chinensis and the C.kwechowensis-C.yunnanensis complex had diverged into two genetic lineages,forming a consistent pattern of southwestern-northern differentiation.Population size of the narrow southwestern lineages of both species have decreased continuously since the late Miocene,whereas the widespread northern lineages have remained stable(C.chinensis) or have even recovered from population bottlenecks(C.kwechowensis-C.yunnanensis complex) during the Quaternary.Compared with C.kwechowensis-C. yunnanensis complex,C.chinensis showed significantly lower genomic diversity and higher inbreeding level.However,C.chinensis carried significantly fewer deleterious mutations than C.kwechowensis-C. yunnanensis complex,as more effective purging selection reduced the accumulation of homozygous variants.We also detected signals of positive selection and adaptive introgression in different lineages,which facilitated the accumulation of favorable variants and formation of local adaptation.Hence,both types of selection and exogenous introgression could have mitigated inbreeding and facilitated survival and persistence of C.chinensis.Overall,our study provides critical insights into lineage differentiation,local adaptation,and the potential for future recovery of endangered trees.

Population genomics reveals demographic history and selection signatures of hazelnut (Corylus)

Hazelnut(Corylus spp.)is known as one of the four famous tree nuts in the world due to its pleasant taste and nutritional benefits.However,hazelnut promotion worldwide is increasingly challenged by global climate change,limiting its production to a few regions.Focusing on the eurytopic Section Phyllochlamys,we conducted whole-genome resequencing of 125 diverse accessions from five geo-ecological zones in Eurasia to elucidate the genomic basis of adaptation and improvement.Population structure inference outlined five distinct genetic lineages corresponding to climate conditions and breeding background,and highlighted the differentiation between European and Asian lineages.Demographic dynamics and ecological niche modeling revealed that Pleistocene climatic oscillations dominantly shaped the extant genetic patterns,and multiple environmental factors have contributed to the lineage divergence.Whole-genome scans identified 279,111,and 164 selective sweeps that underlie local adaptation in Corylus heterophylla,Corylus kweichowensis,and Corylus yunnanensis,respectively.Relevant positively selected genes were mainly involved in regulating signaling pathways,growth and development,and stress resistance.The improvement signatures of hybrid hazelnut were concentrated in 312 and 316 selected genes,when compared to C.heterophylla and Corylus avellana,respectively,including those that regulate protein polymerization,photosynthesis,and response to water deprivation.Among these loci,22 candidate genes were highly associated with the regulation of biological quality.Our study provides insights into evolutionary processes and the molecular basis of how sibling species adapt to contrasting environments,and offers valuable resources for future climate-resilient breeding.

Particulate Amines in the Background Atmosphere of the Yangtze River Delta,China:Concentration,Size Distribution,and Sources

Amines are important for new particle formation and subsequent growth in the atmosphere.Consequently,the processes involved are receiving more attention in recent years.Here,we conduct a field observation in order to investigate the atmospheric particulate amines at a background site in the Yangtze River Delta(YRD)during the summer of 2018.Four amines in PM_(2.5),i.e.,methylamine(MA),dimethylamine(DMA),diethylamine(DEA),and trimethylamine(TMA),were collected,twice daily and analyzed.During the campaign,our measurements found the concentrations of MA,DMA,DEA,and TMA of 15.0±15.0,6.3±6.9,20.4±30.1,and 4.0±5.9 ng m^-(3),respectively,and the four amines correlated well with each other.The concentration of amines appear to be independent of whether they were collected during the day or night.Both MA and DMA exhibited a bimodal size distribution that had peaks at 0.67 and 1.1μm,suggesting amines preferably distribute on submicron particles.Boundary layer height(BLH),relative humidity,and pH of aerosols were found have a negative relationship with amines,while aerosol liquid water content(ALWC)was found to have a positive relationship with amines.The PMF(positive matrix factorization)source apportionment results showed that the main source of amines in Chongming Island was of anthropogenic origin such as industrial and biomass emission,followed by marine sources including sea salt and marine biogenic sources.Given that the YRD region is still suffering from complex atmospheric pollution and that the knowledge on aerosol amines is still limited,more field studies are in urgent need for a better understanding of the pollution characteristics of amines.

Modal analysis of subway tunnel in soft soil during operation

Modal parameters are of great significance in civil engineering because they can characterize the properties of structures and be used for vibration control and structural health monitoring.Subway tunnels are long linear truss structures combined with the mutual cou-pling of the surrounding soil.Therefore,the operational modal analysis of a mutual coupling tunnel is complicate,as is the modal iden-tification of shield tunnels in a time–frequency domain,and these are hot civil engineering topics.Using the shield tunnel of Shanghai metro line No.12 project as a case study,we carried out the vibration response monitoring of a subway tunnel during operation and presented methods to identify structural modal parameters.The modal parameters of lower vibration modes were estimated using response measurements.Modal frequencies and shapes were identified with high precision and accuracy using the orthogonal polynomial clustering algorithm under hammer excitation conditions and the autoregressive-moving-average model under ambient excitation con-ditions.The dynamic behavior of a mutual coupling tunnel presented obvious low frequency characteristics,and the first 9th order mode frequencies were less than 100 Hz.The diagonal values of the modal assurance criteria were all greater than 0.85.The modal parameters can be used for the health monitoring of operational subway tunnels.

Diverse bacterial populations of PM_(2.5) in urban and suburb Shanghai,China

Airborne bacteria play key roles in terrestrial and marine ecosystems and human health,yet our understanding of bacterial communities and their response to the environmental variables lags significantly behind that of other components of PM_(2.5).Here,atmospheric fine particles obtained from urban and suburb Shanghai were analyzed by using the qPCR and Illumina Miseq sequencing.The bacteria with an average concentration of 2.12× 10^(3 )cells/m^(3),were dominated by Sphingomonas,Curvibacter,Acinetobacter,Bradyrhizobium,Methylobacterium,Halomonas,Aliihoeflea,and Phyllobacterium,which were related to the nitrogen,carbon,sulfur cycling and human health risk.Our results provide a global survey of bacterial community across urban,suburb,and high-altitude sites.In Shanghai(China),urban PM2.5 harbour more diverse and dynamic bacterial populations than that in the suburb.The structural equation model explained about 27%,41%,and 20%^78%of the variance found in bacteria diversity,concentration,and discrepant genera among urban and suburb sites.This work furthered the knowledge of diverse bacteria in a coastal Megacity in the Yangtze river delta and emphasized the potential impact of environmental variables on bacterial community structure.