Road Centrality and Landscape Spatial Patterns in Wuhan Metropolitan Area,China

Road network is a corridor system that interacts with surrounding landscapes,and understanding their interaction helps to develop an optimal plan for sustainable transportation and land use.This study investigates the relationships between road centrality and landscape patterns in the Wuhan Metropolitan Area,China.The densities of centrality measures,including closeness,betweenness,and straightness,are calculated by kernel density estimation(KDE).The landscape patterns are characterized by four landscape metrics,including percentage of landscape(PLAND),Shannon′s diversity index(SHDI),mean patch size(MPS),and mean shape index(MSI).Spearman rank correlation analysis is then used to quantify their relationships at both landscape and class levels.The results show that the centrality measures can reflect the hierarchy of road network as they associate with road grade.Further analysis exhibit that as centrality densities increase,the whole landscape becomes more fragmented and regular.At the class level,the forest gradually decreases and becomes fragmented,while the construction land increases and turns to more compact.Therefore,these findings indicate that the ability and potential applications of centrality densities estimated by KDE in quantifying the relationships between roads and landscapes,can provide detailed information and valuable guidance for transportation and land-use planning as well as a new insight into ecological effects of roads.

Infection density pattern of Cardinium affects the responses of bacterial communities in an invasive whitefly under heat conditions

Communities of bacteria,especially symbionts,are vital for the growth and development of insects and other arthropods,including Bemisia tabaci Mediterranean(MED),a destructive and invasive insect pest.However,the infection density patterns and influence factors of bacteria in whiteflies,which mainly include symbionts,remain largely unclear.To reveal the different density patterns of Cardinium in B.tabaci MED popula-tions and the impacts of high temperatures on whiteflies with different Cardinium density infection patterns,2 isofemale lines isolated from B.tabaci MED from the same geo-graphical population of China and from B.tabaci MED collected from other countries and locations were examined using several techniques and methods,including fluorescence in situ hybridization(FISH),quantitative real-time polymerase chain reaction(qPCR),16S rRNA gene sequencing,and 2b-RAD sequencing.The results showed that there were 2 different infection density patterns of Cardinium in B.tabaci MED(including 1 high-density pattern and 1 low-density pattern).For whiteflies with low-density Cardinium,conventional PCR could not detect Cardinium,but the other techniques confirmed that there was a low level of Cardinium within hosts.High temperature significantly decreased the diversity of bacterial communities:the relative titer of Cardinium increased but the density of Rickettsia decreased in the isofemale line with high-density Cardinium.How-ever,high temperature did not influence the diversity and symbiont density in the line with low-density Cardinium.Moreover,high temperature influenced the functions of bacterial communities in whiteflies with high-density Cardinium but did not affect the bacterial functions in whiteflies with low-density Cardinium.Our results provide novel insights into the complex associations between symbionts and host insects.