Nestedness is one of the important patterns in island biogeography,community ecology and conservation biology.However,most previous nestedness studies focus on the taxonomic dimension while neglecting the functional a...Nestedness is one of the important patterns in island biogeography,community ecology and conservation biology.However,most previous nestedness studies focus on the taxonomic dimension while neglecting the functional and phylogenetic processes in generating nestedness.Moreover,few studies have examined the seasonal change of the nestedness and underlying processes.Here,we examined the seasonal nestedness of bird assemblages in taxonomic,functional,and phylogenetic dimensions,and determined the underlying processes of nestedness patterns in the Zhoushan Archipelago,China.We surveyed the occurrence, abundance,and habitats of birds on 40 islands.We calculated taxonomic,functional,and phylogenetic nestedness using WNODF and treeNODF.We determined the processes underlying nestedness by relating nestedness ranks to island characteristics and species traits.The WNODF analyses showed that bird assemblages in winter and summer were both significantly nested.The habitat-by-site matrix was also significantly nested.The nestedness of bird assemblages was significantly correlated with island area,habitat diversity,habitat specificity,minimum area requirement,habitat specificity and hand-wing index(HWI) of birds in both seasons.While the distance to the nearest mainland(DTM) exerted the influence on nestedness in summer,the distance to the nearest larger island(DTNL)affected nestedness only in winter.However,the nestedness of bird assemblages was not caused by passive sampling or human disturbance.The results of treeNODF analyses illustrated that bird assemblages were functionally and phylogenetically nested in summer and winter,but the exact mechanisms were somewhat different in these two seasons.Overall,our results supported the habitat nestedness hypothesis,selective extinction hypothesis,and selective colonization hypothesis in both seasons.From a conservation viewpoint,we should protect islands with large area and diverse habitats,islands close to the mainland,and species with large area requirement and high habitat specificity to prevent local extinction.展开更多
Nestedness is an important part of the theoretical framework of island biogeography and community ecology.However,most previous studies focused on taxonomic dimension and overlooked functional and phylogenetic nestedn...Nestedness is an important part of the theoretical framework of island biogeography and community ecology.However,most previous studies focused on taxonomic dimension and overlooked functional and phylogenetic nestedness.Here,we simultaneously investigated taxonomic,functional,and phylogenetic nestedness of terrestrial mammals on 39 land-bridge islands in the Zhoushan Archipelago,China.As mammals’response to the environment may depend on their body size,we performed analyses for three mammal assemblages separately:overall species,large and medium-sized species,and small species.The taxonomic nestedness was quantified by organizing the species incidence matrix,while the functional and phylogenetic nestedness were estimated by combining the similarity of their ecological traits and phylogeny.Island characteristics(island area,three isolation indices,land use intensity,and habitat diversity)and species traits(body size,litter size,habitat specificity,geographic range size,and minimum area requirement)were used as predictors of nestedness.Overall and small species were significantly nested in 3 facets of nestedness,and results supported the selective extinction,selective colonization,and habitat nestedness hypotheses.Large and medium-sized species were functionally and phylogenetically nested when matrices were ordered by increasing distance to mainland,supporting the selective colonization hypothesis.Overall,differences in nestedness and its underlying mechanisms were detected not only in 3 facets of nestedness but also in the 3 mammal assemblages.Therefore,frameworks that incorporate taxonomic,phylogenetic,and functional nestedness can contribute to a more comprehensive understanding of nestedness processes.Additionally,it also improves our ability to understand the divergent responses of mammal assemblages to the insular environment.展开更多
Nested subset pattern(nestedness)is an important part of the theoretical framework of island biogeography and community ecology.However,most previous studies often used nestedness metrics or randomization algorithms t...Nested subset pattern(nestedness)is an important part of the theoretical framework of island biogeography and community ecology.However,most previous studies often used nestedness metrics or randomization algorithms that are vulnerable to type I error.In this study,we inves-tigated the nestedness of lizard assemblages on 37 islands in the Zhoushan Archipelago,China.We used the line-transect method to survey species occurrence,abundance,and habitat types of lizards on 37 islands during 2 breeding seasons in 2021 and 2022.We applied the nested metric WNODF and the conservative rc null model to control for type I error and quantify the significance of nestedness.Spearman rank cor relations were used to evaluate the role of 4 habitat variables(island area,2 isolation indices,and habitat diversity)and 4 ecological traits(body size,geographic range size,clutch size,and minimum area requirement)in generating nestedness.The results of WNODF analyses showed that lizard assemblages were significantly nested.The habitat-by-site matrix estimated by the program NODF was also significantly nested,support-ing the habitat nestedness hypothesis.The nestedness of lizard assemblages were significantly correlated with island area,habitat diversity.clutch size,and minimum area requirement.Overall,our results suggest that selective extinction and habitat nestedness were the main drivers of lizard nestedness in our system.In contrast,the nestedness of lizard assemblages was not due to passive sampling or selective colonization.To maximize the number of species preserved,our results indicate that we should protect both large islands with diverse habitats and species with largearea requirement and clutch size.展开更多
The limestone region in southwestern Guangxi contains the most typical karst landforms in the world. Due to their destruction, the original forests mainly survive in nature reserves in the form of fragmented areas. Fr...The limestone region in southwestern Guangxi contains the most typical karst landforms in the world. Due to their destruction, the original forests mainly survive in nature reserves in the form of fragmented areas. From June 2009 to September 2010 we conducted an investigation of 13 relatively isolated habitats or sites, selected from each of the 13 nature reserves in southwestern Guangxi, with the least amount of anthropological activity and the largest presence of the original vegetation, in order to study the distribution of birds on forest fragments. The distribution patterns of the birds and the factors which affect them were analyzed by using the 'BINMATNEST' software and the Spearman’s rank correlation analysis, to determine: 1) whether nested patterns of birds in the karst area of southwestern Guangxi exist or not and 2) which factors are correlated with the nested patterns and the effect of these factors on forming nested patterns. The results show that the birds had statistically significant nested patterns in the karst area and the specificity of the habitat of the birds had a significant effect on the nested patterns. We suggest possible reasons for these results, based on the characteristics of the seasonal tropical rain forests in the study area and on neutral theory. We also urgently recommend that close attention be paid to the protection of the diversity of the environment for birds in all fragmented habitats.展开更多
Abstract Nestedness is a pattern frequently reported for faunal assemblages in fragmented systems. Although nestedness has been documented for a wide range of taxa, it is rarely tested in snake assemblages. To arrive ...Abstract Nestedness is a pattern frequently reported for faunal assemblages in fragmented systems. Although nestedness has been documented for a wide range of taxa, it is rarely tested in snake assemblages. To arrive at robust generalizations about processes and mechanisms structuring island biotas, it is important to examine under-represented taxa such as snakes for the insights they may offer. We tested for the existence of nestedness and underlying causal mechanisms using snake data collected on islands in the Thousand Island Lake, China. We used the line-transect method to survey snake occupancy and abundance on 20 islands during two breeding seasons in 2009 and 2010. We used the recently developed metric WNODF to estimate nestedness. We used Spearman rank correlations to examine the associations of nestedness and habitat variables （area, isolation, and habitat diversity） as well as life-history traits （body size, clutch size, geographical range size and area requirement） related to species extinction and immigration tendencies. Snake assemblages were significantly nested and were shaped by extinction processes mediated through area effects and habitat nestedness. The nestedness of snake assemblages was not due to passive sampling or selective colonization. From a conservation viewpoint, our results indicate that we should protect both the largest island with the most species-rich community and habitat-rich islands to maximize the number of species preserved .展开更多
Nestedness is an important pattern frequently reported for species assemblages on islands or fragmented systems.However,to date,there are few studies that comprehensively investigated faunal nestedness and underlying ...Nestedness is an important pattern frequently reported for species assemblages on islands or fragmented systems.However,to date,there are few studies that comprehensively investigated faunal nestedness and underlying processes in urbanized landscapes.In this study,we examined the nestedness of bird assemblages and its underlying causal mechanisms in 37 urban parks in Nanjing,China.We used the line-transect method to survey birds from April 2019 to January 2020.We used the Weighted Nestedness metric based on Overlap and Decreasing Fill(WNODF)to estimate the nestedness of bird assemblages.We applied spearman partial correlation test to examine the relationships between nestedness ranks of sites and park characteristics(area,isolation,anthropogenic noise,number of habitat types,and building index),as well as between nestedness ranks of species and their ecological traits(body size,geographic range size,clutch size,minimum area requirement,dispersal ratio,and habitat specificity).We found that bird assemblages in urban parks were significantly nested.Park area,habitat diversity,building index,habitat specificity,and minimum area requirement of birds were significantly correlated with nestedness.Therefore,the nestedness of bird assemblages was caused by selective extinction,habitat nestedness,and urbanization.However,the nestedness of bird assemblages did not result from passive sampling,selective colonization,or human disturbance.Overall,to maximize the number of species preserved in our system,conservation priority should be given to parks with large area,rich habitat diversity,and less building index.From a species perspective,we should focus on species with large area requirement and high habitat specificity for their effective conservation.展开更多
An understanding of the knowledge creation and diffusion process in the organizational context is extremely relevant. Because from this understanding, organizations can restructure processes, reorient teams and implem...An understanding of the knowledge creation and diffusion process in the organizational context is extremely relevant. Because from this understanding, organizations can restructure processes, reorient teams and implement methodologies to assist in the construction of an evolutionary process of knowledge creation and diffusion aimed at sustainable growth and innovation. The theory of complex social networks has been applied in several fields to help understand organizational cognitive processes. However, these approaches still insipiently consider the analysis of the nestedness and modularity of the studied networks. In this article, we presented an approach that sought to identify patterns of nestedness and modularity in networks of affiliation of people in projects in the organizational context. The study sought to identify these patterns in affiliation networks in a public organization providing information technology services in the period from 2006 to 2013. The detection of these patterns was performed using the NODF (Nestedness metric based on Overlap and Decreasing Fill) algorithm described by <a href="#ref1">[1]</a>. The nestedness and modularity metrics can influence patterns of knowledge creation and diffusion in formal and informal networks constituted for the execution of projects in organizations. This study showed that the network structures of the organization during the study period presented a high degree of nestedness, and it was possible to identify combined structures of nestedness and modularity.展开更多
We compare and contrast asymmetry and nestedness, two concepts used in the characterisation of the specialist-generalist balance in bipartite ecological interaction networks. Our analysis is relevant to mutualistic ne...We compare and contrast asymmetry and nestedness, two concepts used in the characterisation of the specialist-generalist balance in bipartite ecological interaction networks. Our analysis is relevant to mutualistic networks such as those consisting of flowering plants and pollinators, or fruiting plants and frugivores, or antagonistic networks such as those consisting of plants and herbivores, in an ecological community. We shall refer to the two sets of species in the bipartite network as plants and animals, the usual but not the only ecological situation. By asymmetry we mean either connectivity asymmetry or dependence asymmetry, which are essentially equivalent. Asymmetry expresses two attributes: generalists interact preferentially with specialists, and specialists avoid interacting with each other. Nested patterns, in principle, should express these same two features and one more: the presence of a core of interactions among generalists. We compute the full set of perfectly nested patterns that are possible in an L × L matrix with N interactions representing an ecological network of L plants and L animals, and point out that the number of nested arrangements grows exponentially with N. In addition, we analyse asymmetry for the full set of perfectly nested patterns, and identify extremes of asymmetry inside the universe of nested patterns. The minimal asymmetry is marked by a modular core of interactions between species that are neither specialists nor generalists. On the other hand, the case of maximal asymmetry is formed by a set of few generalists and many specialists with equal connectivity. The stereotypic case of nestedness with a core of interactions among generalists has intermediate asymmetry.展开更多
Nestedness has been a research focus in fields of island biogeography and community ecology in recent decades. Although nestedness of faunal assemblages has been investigated in natural wetlands, it remains largely un...Nestedness has been a research focus in fields of island biogeography and community ecology in recent decades. Although nestedness of faunal assemblages has been investigated in natural wetlands, it remains largely unknown whether and why waterbird communities in artificial wetlands follow n ested patter ns. We exami ned the existence of n ested ness and un derlyi ng drivers in waterbird comm un ities in subside nee wetlands that are recently created by large-scale un derground coal mining in the North China Plain. Twelve point-count surveys for waterbirds were undertaken approximately every 2 weeks in 55 subside nee wetla nds from September 2016 to April 2017. We used the metric WNODF to estimate nestedness of the assemblages. Partial Spearman rank correlations were performed to examine the association between the nestedness and habitat variables (wetland area, landscape connectivity, wetland age, and habitat diversity) as well as life-history traits (body size, clutch size, dispersal ratio, geographical range size, and migrant status) related to species exti notion risk and colon izati on rate. Waterbird assemblages in the subside nee wetla nds were significantly nested. After controlling for other independent variables, the magnitude of nestedness was significantly and negatively correlated with wetland area and species trait linked to extinction risk (i.e., geographical range size). Our results indicate that selective extinction may be the main driver of the nestedness of waterbird assemblages in our study system. However, the nestedness was not due to passive sampling, selective colonization, or habitat diversity. From a conservation viewpoint, both large wetlands and waterbirds with a small geographic range should be protected to maximize the preserved species richness.展开更多
Aims Nestedness is a characteristic of insular metacommunity structure.Relatively few studies,however,have attempted to evaluate temporal changes in nestedness,or elucidate the mechanisms underlying nestedness.I evalu...Aims Nestedness is a characteristic of insular metacommunity structure.Relatively few studies,however,have attempted to evaluate temporal changes in nestedness,or elucidate the mechanisms underlying nestedness.I evaluated both spatial and temporal patterns of nestedness in the insular floras of four archipelagoes of small islands in the Bahamas and the potential underlying environmental gradients.Methods The NODF(a nestedness metric based on overlap and decreasing fill)and the matrix temperature measure,T,were used to quantify nestedness in insular floras on small islands near Abaco,Andros,Great Exuma and the Exuma Cays,Bahamas.Two different null models were employed for each nestedness measure.Six environmental variables were evaluated in relation to nestedness by ordering islands according to gradients and recalculating NODF scores.Important Findings All archipelagoes were significantly nested.Nestedness among sites contributed more to overall nestedness than did nestedness among species.NODF scores varied among archipelagoes,but were surprisingly constant over time.Ordering islands by vegetated area yielded the highest nestedness scores for three archipelagoes;ordering islands by protection from exposure yielded the highest nestedness score for one archipelago.Nestedness scores varied little over time even though species compositions changed,indicating that extinctions occurred in a deterministic manner.The relative importance of area suggests extinction is an important mechanism in producing nestedness.Attempting to determine the relative importance of immigrations or extinctions requires some assumptions,however,and both processes are likely cumulative in most cases.展开更多
It has been suggested that the importance of network architecture to species diversity and stability should be based on preference networks(comprised of niche differentiations),rather than observational networks,becau...It has been suggested that the importance of network architecture to species diversity and stability should be based on preference networks(comprised of niche differentiations),rather than observational networks,because species abundance may significantly affect interaction frequencies.Considering that resource abundance is usually greater for herbivores than parasites,we hypothesize that the abundance effect is stronger for parasitic than herbivory interactions.To test this hypothesis,we collected 80 quantitative observational networks including 34 herbivorous and 46 parasitic networks from the published literature,and derived preference networks by removing the effects of species abundance.We then determined the network nestedness using both weighted NODF and spectral radius.We also determined species degree distribution,interaction evenness,weighted connectance and robustness for both observational and preference networks.The observational networks(including both herbivory and parasitic networks)were more nested judged by weighted NODF than spectral radius.Preference networks were less nested for parasitic than herbivory networks in terms of both weighted NODF and spectral radius,possibly because removing the abundance effect increased interaction evenness.These trends indicate that the abundance effect on network nestedness is stronger for parasitic than herbivory networks.Weighted connectance and robustness were greater in most preference networks than observational networks,indicating that preference networks may have high network stability and community persistence compared with observational ones.The data indicate that future network analyses should not only address the structural difference between mutualistic and antagonistic interactions,but also between herbivory and parasitic interactions.展开更多
The concept of nestedness originated from the field of biogeography decades ago and has been widely used in metacommunities and biological interaction networks,but there is still a lack of research within local commun...The concept of nestedness originated from the field of biogeography decades ago and has been widely used in metacommunities and biological interaction networks,but there is still a lack of research within local communities.Moreover,studies on nestedness usually rarely incorporate the functional traits of the species and the environmental characteristics of the sites.In this study,we constructed a species presence–absence matrix of a 50-ha forest plot,used the simulated annealing algorithm to reveal the maximum nested structure and further tested the significance of nestedness patterns by constructing null ensembles.The nested ranks were used to represent the orders of species and quadrats in the maximum nestedness matrix.The regression tree analysis was used to reveal the relationships of nested ranks with environmental factors and functional traits.We found that the co-occurrence pattern of local plant communities was significantly nested.The regression tree results showed that the nested ranks of quadrats were determined by soil available phosphorus,soil water content,soil organic carbon and soil pH.Intraspecific variation of functional traits,including leaf C,leaf pH,leaf dry matter content and maximum photosynthetic rate rather than means of functional traits,provided a better explanation for the formation of species’nested ranks.Understanding the causes of species and quadrats nested ranks provides novel lens and useful insights into ecological processes underlying nestedness,and further improves our knowledge of how local plant communities are assembled.展开更多
The nestedness property has become an increasingly important means for devising efficient algorithms for network location problems.There have been attempts to explore the nestedness property of network location proble...The nestedness property has become an increasingly important means for devising efficient algorithms for network location problems.There have been attempts to explore the nestedness property of network location problems with some special cases of the convex ordered median objectives.However,there is little research on the nestedness property for those problems with the concave ordered median objectives.This paper constructs a tree network T and shows that the nestedness property cannot hold for the concave ordered median problem,which fills a gap in the research on the nestedness property.Finally,the authors pose an open problem on identifying the nestedness property for the continuous strategic ordered median problem.展开更多
BACKGROUND The impact of psychiatric disorder,especially depression,on the prognosis of sarcopenic patients is gaining prominence.Yet,there have been very few studies focusing on this issue,let alone the related targe...BACKGROUND The impact of psychiatric disorder,especially depression,on the prognosis of sarcopenic patients is gaining prominence.Yet,there have been very few studies focusing on this issue,let alone the related targeted mental health prevention.This cohort-based nested case-control study is geared to compare risk of depression and the depression-related ambulatory care utilization for sarcopenia persons with and without receiving add-on Chinese herbal medicines(CHMs)treatment.AIM To compare risk of depression and the depression-related ambulatory care utili-zation for sarcopenia persons with and without receiving add-on CHMs treat-ment.METHODS In the beginning,we recruited those aged 20-70 years with newly diagnosed sarcopenia and free of depression between 2002 and 2010 from a nationwide insurance database.From them,we identified cases with depression onset occurring after sarcopenia until December 31,2013.To cautiously isolate the effect of CHMs,we established the matched sets of treated and untreated subjects with CHMs use by randomly frequency matching.A conditional logistic regression was executed to explore the association of CHMs to depression risk,and the frequency and costs of depression-related ambulatory care were compared using Mann-Whitney U test.RESULTS Addition of CHMs to routine care of sarcopenia notably correlated with a lower risk of depression.A remarkable effect of CHMs in reducing depression was detected when sarcopenia subjects received CHMs for more than three years,lowering depression risk by as much as 65%.As compared to CHMs users,the non-CHMs users indeed incurred higher frequency and costs of depression-related ambulatory care after depression attack(P<0.05).Notably,the costs for per depression-related ambulatory care profoundly increased with the years after depression attack.CONCLUSION Sarcopenic patients can greatly benefit from add-on CHMs treatment,underscoring the urgent need for interdisciplinary collaboration and proactive treatment planning.展开更多
Sparse array design has significant implications for improving the accuracy of direction of arrival(DOA)estimation of non-circular(NC)signals.We propose an extended nested array with a filled sensor(ENAFS)based on the...Sparse array design has significant implications for improving the accuracy of direction of arrival(DOA)estimation of non-circular(NC)signals.We propose an extended nested array with a filled sensor(ENAFS)based on the hole-filling strategy.Specifically,we first introduce the improved nested array(INA)and prove its properties.Subsequently,we extend the sum-difference coarray(SDCA)by adding an additional sensor to fill the holes.Thus the larger uniform degrees of freedom(uDOFs)and virtual array aperture(VAA)can be abtained,and the ENAFS is designed.Finally,the simulation results are given to verify the superiority of the proposed ENAFS in terms of DOF,mutual coupling and estimation performance.展开更多
This paper introduces damping amplifier friction vibration absorbers(DAFVAs),compound damping amplifier friction vibration absorbers(CDAFVAs),nested damping amplifier friction vibration absorbers(NDAFVAs),and levered ...This paper introduces damping amplifier friction vibration absorbers(DAFVAs),compound damping amplifier friction vibration absorbers(CDAFVAs),nested damping amplifier friction vibration absorbers(NDAFVAs),and levered damping amplifier friction vibration absorbers(LDAFVAs)for controlling the structural vibrations and addressing the limitations of conventional tuned mass dampers(TMDs)and frictiontuned mass dampers(FTMDs).The closed-form analytical solution for the optimized design parameters is obtained using the H_(2)and H_(∞)optimization approaches.The efficiency of the recently established closed-form equations for the optimal design parameters is confirmed by the analytical examination.The closed form formulas for the dynamic responses of the main structure and the vibration absorbers are derived using the transfer matrix formulations.The foundation is provided by the harmonic and random-white noise excitations.Moreover,the effectiveness of the innovative dampers has been validated through numerical analysis.The optimal DAFVAs,CDAFVAs,NDAFVAs,and LDAFVAs exhibit at least 30%lower vibration reduction capacity compared with the optimal TMD.To demonstrate the effectiveness of the damping amplification mechanism,the novel absorbers are compared with a conventional FTMD.The results show that the optimized novel absorbers achieve at least 91%greater vibration reduction than the FTMD.These results show how the suggested designs might strengthen the structure's resilience to dynamic loads.展开更多
Petroleum hydrocarbon pollution is a global concern,particularly in coastal environments.Polycyclic aromatic hydrocarbons(PAHs) are regarded as the most toxic components of petroleum hydrocarbons.In this study,the bio...Petroleum hydrocarbon pollution is a global concern,particularly in coastal environments.Polycyclic aromatic hydrocarbons(PAHs) are regarded as the most toxic components of petroleum hydrocarbons.In this study,the biomonitoring and ranking effects of petroleum hydrocarbons and PAHs on the marine fish model Oryzias melastigma embryos were determined in the Jiulong River Estuary(JRE) and its adjacent waters in China.The results showed that the levels of petroleum hydrocarbons from almost all sites met the primary standard for marine seawater quality,and the concentrations of the 16 priority PAHs in the surface seawater were lower compared with those in other coastal areas worldwide.A new fish expert system based on the embryotoxicity of O.melastigma(OME-FES) was developed and applied in the field to evaluate the biological effects of petroleum hydrocarbons and PAHs.The selected physiological index and molecular indicators in OME-FES were appropriate biomarkers for indicating the harmful effects of petroleum hydrocarbons and PAHs.The outcome of OME-FES revealed that the biological effect levels of the sampling sites ranged from level Ⅰ(no stress) to level Ⅲ(medium stress),which is further corroborated by the findings of nested analysis of variance(ANOVA) models.Our results suggest that the OME-FES is an effective tool for evaluating and ranking the biological effects of marine petroleum hydrocarbons and PAHs.This method may also be applied to evaluate other marine pollutants based on its framework.展开更多
The Hot Universe Baryon Surveyor (HUBS) mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution. In this paper, we report the latest progres...The Hot Universe Baryon Surveyor (HUBS) mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution. In this paper, we report the latest progress in the design and construction of nested X-ray telescopes which were designed to use a three-stage conic-approximation type assembly to simplify the manufacturing process. The mirror substrate is made using the thermal glass slumping method, with mirrors characterized by a root-mean-square roughness of 0.3 nm, with expected high reflectivity and good thermal stability. We also discuss methods of telescope construction and conduct a deformation analysis of the manufactured mirror. The in situ measurement system program is developed to guide the telescope assembly process.展开更多
基金supported by the National Natural Science Foundation of China (32271734)。
文摘Nestedness is one of the important patterns in island biogeography,community ecology and conservation biology.However,most previous nestedness studies focus on the taxonomic dimension while neglecting the functional and phylogenetic processes in generating nestedness.Moreover,few studies have examined the seasonal change of the nestedness and underlying processes.Here,we examined the seasonal nestedness of bird assemblages in taxonomic,functional,and phylogenetic dimensions,and determined the underlying processes of nestedness patterns in the Zhoushan Archipelago,China.We surveyed the occurrence, abundance,and habitats of birds on 40 islands.We calculated taxonomic,functional,and phylogenetic nestedness using WNODF and treeNODF.We determined the processes underlying nestedness by relating nestedness ranks to island characteristics and species traits.The WNODF analyses showed that bird assemblages in winter and summer were both significantly nested.The habitat-by-site matrix was also significantly nested.The nestedness of bird assemblages was significantly correlated with island area,habitat diversity,habitat specificity,minimum area requirement,habitat specificity and hand-wing index(HWI) of birds in both seasons.While the distance to the nearest mainland(DTM) exerted the influence on nestedness in summer,the distance to the nearest larger island(DTNL)affected nestedness only in winter.However,the nestedness of bird assemblages was not caused by passive sampling or human disturbance.The results of treeNODF analyses illustrated that bird assemblages were functionally and phylogenetically nested in summer and winter,but the exact mechanisms were somewhat different in these two seasons.Overall,our results supported the habitat nestedness hypothesis,selective extinction hypothesis,and selective colonization hypothesis in both seasons.From a conservation viewpoint,we should protect islands with large area and diverse habitats,islands close to the mainland,and species with large area requirement and high habitat specificity to prevent local extinction.
基金supported by the National Natural Science Foundation of China(32271734 and 31971545).
文摘Nestedness is an important part of the theoretical framework of island biogeography and community ecology.However,most previous studies focused on taxonomic dimension and overlooked functional and phylogenetic nestedness.Here,we simultaneously investigated taxonomic,functional,and phylogenetic nestedness of terrestrial mammals on 39 land-bridge islands in the Zhoushan Archipelago,China.As mammals’response to the environment may depend on their body size,we performed analyses for three mammal assemblages separately:overall species,large and medium-sized species,and small species.The taxonomic nestedness was quantified by organizing the species incidence matrix,while the functional and phylogenetic nestedness were estimated by combining the similarity of their ecological traits and phylogeny.Island characteristics(island area,three isolation indices,land use intensity,and habitat diversity)and species traits(body size,litter size,habitat specificity,geographic range size,and minimum area requirement)were used as predictors of nestedness.Overall and small species were significantly nested in 3 facets of nestedness,and results supported the selective extinction,selective colonization,and habitat nestedness hypotheses.Large and medium-sized species were functionally and phylogenetically nested when matrices were ordered by increasing distance to mainland,supporting the selective colonization hypothesis.Overall,differences in nestedness and its underlying mechanisms were detected not only in 3 facets of nestedness but also in the 3 mammal assemblages.Therefore,frameworks that incorporate taxonomic,phylogenetic,and functional nestedness can contribute to a more comprehensive understanding of nestedness processes.Additionally,it also improves our ability to understand the divergent responses of mammal assemblages to the insular environment.
基金supported by the National Natural Science Foundation of China(31971545 and 32271734).
文摘Nested subset pattern(nestedness)is an important part of the theoretical framework of island biogeography and community ecology.However,most previous studies often used nestedness metrics or randomization algorithms that are vulnerable to type I error.In this study,we inves-tigated the nestedness of lizard assemblages on 37 islands in the Zhoushan Archipelago,China.We used the line-transect method to survey species occurrence,abundance,and habitat types of lizards on 37 islands during 2 breeding seasons in 2021 and 2022.We applied the nested metric WNODF and the conservative rc null model to control for type I error and quantify the significance of nestedness.Spearman rank cor relations were used to evaluate the role of 4 habitat variables(island area,2 isolation indices,and habitat diversity)and 4 ecological traits(body size,geographic range size,clutch size,and minimum area requirement)in generating nestedness.The results of WNODF analyses showed that lizard assemblages were significantly nested.The habitat-by-site matrix estimated by the program NODF was also significantly nested,support-ing the habitat nestedness hypothesis.The nestedness of lizard assemblages were significantly correlated with island area,habitat diversity.clutch size,and minimum area requirement.Overall,our results suggest that selective extinction and habitat nestedness were the main drivers of lizard nestedness in our system.In contrast,the nestedness of lizard assemblages was not due to passive sampling or selective colonization.To maximize the number of species preserved,our results indicate that we should protect both large islands with diverse habitats and species with largearea requirement and clutch size.
基金financed by the National Nature Science Foundation of China (Grant Nos. 30970381,31172123)
文摘The limestone region in southwestern Guangxi contains the most typical karst landforms in the world. Due to their destruction, the original forests mainly survive in nature reserves in the form of fragmented areas. From June 2009 to September 2010 we conducted an investigation of 13 relatively isolated habitats or sites, selected from each of the 13 nature reserves in southwestern Guangxi, with the least amount of anthropological activity and the largest presence of the original vegetation, in order to study the distribution of birds on forest fragments. The distribution patterns of the birds and the factors which affect them were analyzed by using the 'BINMATNEST' software and the Spearman’s rank correlation analysis, to determine: 1) whether nested patterns of birds in the karst area of southwestern Guangxi exist or not and 2) which factors are correlated with the nested patterns and the effect of these factors on forming nested patterns. The results show that the birds had statistically significant nested patterns in the karst area and the specificity of the habitat of the birds had a significant effect on the nested patterns. We suggest possible reasons for these results, based on the characteristics of the seasonal tropical rain forests in the study area and on neutral theory. We also urgently recommend that close attention be paid to the protection of the diversity of the environment for birds in all fragmented habitats.
基金We thank two anonymous reviewers for helpful comments on earlier version of the manuscript. We are grateful to Chunan Forestry Bureau and the Thousand Island Lake National Forest Park for permits necessary to conduct the research. This study was supported by the National Natural Science Foundation of China （Nos. 31100394, 31170397）, the China Postdoctoral Science Foundation （No. 20070411192）, Zhejiang Provincial Postdoctoral Science Foundation, and the Fundamental Research Funds for the Central Universities.
文摘Abstract Nestedness is a pattern frequently reported for faunal assemblages in fragmented systems. Although nestedness has been documented for a wide range of taxa, it is rarely tested in snake assemblages. To arrive at robust generalizations about processes and mechanisms structuring island biotas, it is important to examine under-represented taxa such as snakes for the insights they may offer. We tested for the existence of nestedness and underlying causal mechanisms using snake data collected on islands in the Thousand Island Lake, China. We used the line-transect method to survey snake occupancy and abundance on 20 islands during two breeding seasons in 2009 and 2010. We used the recently developed metric WNODF to estimate nestedness. We used Spearman rank correlations to examine the associations of nestedness and habitat variables （area, isolation, and habitat diversity） as well as life-history traits （body size, clutch size, geographical range size and area requirement） related to species extinction and immigration tendencies. Snake assemblages were significantly nested and were shaped by extinction processes mediated through area effects and habitat nestedness. The nestedness of snake assemblages was not due to passive sampling or selective colonization. From a conservation viewpoint, our results indicate that we should protect both the largest island with the most species-rich community and habitat-rich islands to maximize the number of species preserved .
基金Supported by the National Natural Science Foundation of China(31770462 and 31971545)Natural Science Foundation of Zhejiang Province(LZ18C030002).
文摘Nestedness is an important pattern frequently reported for species assemblages on islands or fragmented systems.However,to date,there are few studies that comprehensively investigated faunal nestedness and underlying processes in urbanized landscapes.In this study,we examined the nestedness of bird assemblages and its underlying causal mechanisms in 37 urban parks in Nanjing,China.We used the line-transect method to survey birds from April 2019 to January 2020.We used the Weighted Nestedness metric based on Overlap and Decreasing Fill(WNODF)to estimate the nestedness of bird assemblages.We applied spearman partial correlation test to examine the relationships between nestedness ranks of sites and park characteristics(area,isolation,anthropogenic noise,number of habitat types,and building index),as well as between nestedness ranks of species and their ecological traits(body size,geographic range size,clutch size,minimum area requirement,dispersal ratio,and habitat specificity).We found that bird assemblages in urban parks were significantly nested.Park area,habitat diversity,building index,habitat specificity,and minimum area requirement of birds were significantly correlated with nestedness.Therefore,the nestedness of bird assemblages was caused by selective extinction,habitat nestedness,and urbanization.However,the nestedness of bird assemblages did not result from passive sampling,selective colonization,or human disturbance.Overall,to maximize the number of species preserved in our system,conservation priority should be given to parks with large area,rich habitat diversity,and less building index.From a species perspective,we should focus on species with large area requirement and high habitat specificity for their effective conservation.
文摘An understanding of the knowledge creation and diffusion process in the organizational context is extremely relevant. Because from this understanding, organizations can restructure processes, reorient teams and implement methodologies to assist in the construction of an evolutionary process of knowledge creation and diffusion aimed at sustainable growth and innovation. The theory of complex social networks has been applied in several fields to help understand organizational cognitive processes. However, these approaches still insipiently consider the analysis of the nestedness and modularity of the studied networks. In this article, we presented an approach that sought to identify patterns of nestedness and modularity in networks of affiliation of people in projects in the organizational context. The study sought to identify these patterns in affiliation networks in a public organization providing information technology services in the period from 2006 to 2013. The detection of these patterns was performed using the NODF (Nestedness metric based on Overlap and Decreasing Fill) algorithm described by <a href="#ref1">[1]</a>. The nestedness and modularity metrics can influence patterns of knowledge creation and diffusion in formal and informal networks constituted for the execution of projects in organizations. This study showed that the network structures of the organization during the study period presented a high degree of nestedness, and it was possible to identify combined structures of nestedness and modularity.
文摘We compare and contrast asymmetry and nestedness, two concepts used in the characterisation of the specialist-generalist balance in bipartite ecological interaction networks. Our analysis is relevant to mutualistic networks such as those consisting of flowering plants and pollinators, or fruiting plants and frugivores, or antagonistic networks such as those consisting of plants and herbivores, in an ecological community. We shall refer to the two sets of species in the bipartite network as plants and animals, the usual but not the only ecological situation. By asymmetry we mean either connectivity asymmetry or dependence asymmetry, which are essentially equivalent. Asymmetry expresses two attributes: generalists interact preferentially with specialists, and specialists avoid interacting with each other. Nested patterns, in principle, should express these same two features and one more: the presence of a core of interactions among generalists. We compute the full set of perfectly nested patterns that are possible in an L × L matrix with N interactions representing an ecological network of L plants and L animals, and point out that the number of nested arrangements grows exponentially with N. In addition, we analyse asymmetry for the full set of perfectly nested patterns, and identify extremes of asymmetry inside the universe of nested patterns. The minimal asymmetry is marked by a modular core of interactions between species that are neither specialists nor generalists. On the other hand, the case of maximal asymmetry is formed by a set of few generalists and many specialists with equal connectivity. The stereotypic case of nestedness with a core of interactions among generalists has intermediate asymmetry.
基金the National Natural Science Foundation of China [31770571, 31770462, and 31471981]the Fundamental Research Funds for the Central Universities [2016QNA6001]Zhejiang Provincial Natural Science Foundation [LZ18C030002).
文摘Nestedness has been a research focus in fields of island biogeography and community ecology in recent decades. Although nestedness of faunal assemblages has been investigated in natural wetlands, it remains largely unknown whether and why waterbird communities in artificial wetlands follow n ested patter ns. We exami ned the existence of n ested ness and un derlyi ng drivers in waterbird comm un ities in subside nee wetlands that are recently created by large-scale un derground coal mining in the North China Plain. Twelve point-count surveys for waterbirds were undertaken approximately every 2 weeks in 55 subside nee wetla nds from September 2016 to April 2017. We used the metric WNODF to estimate nestedness of the assemblages. Partial Spearman rank correlations were performed to examine the association between the nestedness and habitat variables (wetland area, landscape connectivity, wetland age, and habitat diversity) as well as life-history traits (body size, clutch size, dispersal ratio, geographical range size, and migrant status) related to species exti notion risk and colon izati on rate. Waterbird assemblages in the subside nee wetla nds were significantly nested. After controlling for other independent variables, the magnitude of nestedness was significantly and negatively correlated with wetland area and species trait linked to extinction risk (i.e., geographical range size). Our results indicate that selective extinction may be the main driver of the nestedness of waterbird assemblages in our study system. However, the nestedness was not due to passive sampling, selective colonization, or habitat diversity. From a conservation viewpoint, both large wetlands and waterbirds with a small geographic range should be protected to maximize the preserved species richness.
基金This work was supported by National Geographic Society grants(7447-03 and 8137-06)to the author.
文摘Aims Nestedness is a characteristic of insular metacommunity structure.Relatively few studies,however,have attempted to evaluate temporal changes in nestedness,or elucidate the mechanisms underlying nestedness.I evaluated both spatial and temporal patterns of nestedness in the insular floras of four archipelagoes of small islands in the Bahamas and the potential underlying environmental gradients.Methods The NODF(a nestedness metric based on overlap and decreasing fill)and the matrix temperature measure,T,were used to quantify nestedness in insular floras on small islands near Abaco,Andros,Great Exuma and the Exuma Cays,Bahamas.Two different null models were employed for each nestedness measure.Six environmental variables were evaluated in relation to nestedness by ordering islands according to gradients and recalculating NODF scores.Important Findings All archipelagoes were significantly nested.Nestedness among sites contributed more to overall nestedness than did nestedness among species.NODF scores varied among archipelagoes,but were surprisingly constant over time.Ordering islands by vegetated area yielded the highest nestedness scores for three archipelagoes;ordering islands by protection from exposure yielded the highest nestedness score for one archipelago.Nestedness scores varied little over time even though species compositions changed,indicating that extinctions occurred in a deterministic manner.The relative importance of area suggests extinction is an important mechanism in producing nestedness.Attempting to determine the relative importance of immigrations or extinctions requires some assumptions,however,and both processes are likely cumulative in most cases.
基金This study was financially supported by National Natural Science Foundation of China(grant nos.32071605,31530007 and 31870417).
文摘It has been suggested that the importance of network architecture to species diversity and stability should be based on preference networks(comprised of niche differentiations),rather than observational networks,because species abundance may significantly affect interaction frequencies.Considering that resource abundance is usually greater for herbivores than parasites,we hypothesize that the abundance effect is stronger for parasitic than herbivory interactions.To test this hypothesis,we collected 80 quantitative observational networks including 34 herbivorous and 46 parasitic networks from the published literature,and derived preference networks by removing the effects of species abundance.We then determined the network nestedness using both weighted NODF and spectral radius.We also determined species degree distribution,interaction evenness,weighted connectance and robustness for both observational and preference networks.The observational networks(including both herbivory and parasitic networks)were more nested judged by weighted NODF than spectral radius.Preference networks were less nested for parasitic than herbivory networks in terms of both weighted NODF and spectral radius,possibly because removing the abundance effect increased interaction evenness.These trends indicate that the abundance effect on network nestedness is stronger for parasitic than herbivory networks.Weighted connectance and robustness were greater in most preference networks than observational networks,indicating that preference networks may have high network stability and community persistence compared with observational ones.The data indicate that future network analyses should not only address the structural difference between mutualistic and antagonistic interactions,but also between herbivory and parasitic interactions.
基金This study was funded by the National Science Foundation of China(31925027)the Fundamental Research Funds for the Central Universities(20lgpy116,2021qntd18).
文摘The concept of nestedness originated from the field of biogeography decades ago and has been widely used in metacommunities and biological interaction networks,but there is still a lack of research within local communities.Moreover,studies on nestedness usually rarely incorporate the functional traits of the species and the environmental characteristics of the sites.In this study,we constructed a species presence–absence matrix of a 50-ha forest plot,used the simulated annealing algorithm to reveal the maximum nested structure and further tested the significance of nestedness patterns by constructing null ensembles.The nested ranks were used to represent the orders of species and quadrats in the maximum nestedness matrix.The regression tree analysis was used to reveal the relationships of nested ranks with environmental factors and functional traits.We found that the co-occurrence pattern of local plant communities was significantly nested.The regression tree results showed that the nested ranks of quadrats were determined by soil available phosphorus,soil water content,soil organic carbon and soil pH.Intraspecific variation of functional traits,including leaf C,leaf pH,leaf dry matter content and maximum photosynthetic rate rather than means of functional traits,provided a better explanation for the formation of species’nested ranks.Understanding the causes of species and quadrats nested ranks provides novel lens and useful insights into ecological processes underlying nestedness,and further improves our knowledge of how local plant communities are assembled.
基金supported by the Macao Foundation under Grant No.0249National Natural Science Foundation of China under Grant No.70901050
文摘The nestedness property has become an increasingly important means for devising efficient algorithms for network location problems.There have been attempts to explore the nestedness property of network location problems with some special cases of the convex ordered median objectives.However,there is little research on the nestedness property for those problems with the concave ordered median objectives.This paper constructs a tree network T and shows that the nestedness property cannot hold for the concave ordered median problem,which fills a gap in the research on the nestedness property.Finally,the authors pose an open problem on identifying the nestedness property for the continuous strategic ordered median problem.
文摘BACKGROUND The impact of psychiatric disorder,especially depression,on the prognosis of sarcopenic patients is gaining prominence.Yet,there have been very few studies focusing on this issue,let alone the related targeted mental health prevention.This cohort-based nested case-control study is geared to compare risk of depression and the depression-related ambulatory care utilization for sarcopenia persons with and without receiving add-on Chinese herbal medicines(CHMs)treatment.AIM To compare risk of depression and the depression-related ambulatory care utili-zation for sarcopenia persons with and without receiving add-on CHMs treat-ment.METHODS In the beginning,we recruited those aged 20-70 years with newly diagnosed sarcopenia and free of depression between 2002 and 2010 from a nationwide insurance database.From them,we identified cases with depression onset occurring after sarcopenia until December 31,2013.To cautiously isolate the effect of CHMs,we established the matched sets of treated and untreated subjects with CHMs use by randomly frequency matching.A conditional logistic regression was executed to explore the association of CHMs to depression risk,and the frequency and costs of depression-related ambulatory care were compared using Mann-Whitney U test.RESULTS Addition of CHMs to routine care of sarcopenia notably correlated with a lower risk of depression.A remarkable effect of CHMs in reducing depression was detected when sarcopenia subjects received CHMs for more than three years,lowering depression risk by as much as 65%.As compared to CHMs users,the non-CHMs users indeed incurred higher frequency and costs of depression-related ambulatory care after depression attack(P<0.05).Notably,the costs for per depression-related ambulatory care profoundly increased with the years after depression attack.CONCLUSION Sarcopenic patients can greatly benefit from add-on CHMs treatment,underscoring the urgent need for interdisciplinary collaboration and proactive treatment planning.
基金supported by China National Science Foundations(Nos.62371225,62371227)。
文摘Sparse array design has significant implications for improving the accuracy of direction of arrival(DOA)estimation of non-circular(NC)signals.We propose an extended nested array with a filled sensor(ENAFS)based on the hole-filling strategy.Specifically,we first introduce the improved nested array(INA)and prove its properties.Subsequently,we extend the sum-difference coarray(SDCA)by adding an additional sensor to fill the holes.Thus the larger uniform degrees of freedom(uDOFs)and virtual array aperture(VAA)can be abtained,and the ENAFS is designed.Finally,the simulation results are given to verify the superiority of the proposed ENAFS in terms of DOF,mutual coupling and estimation performance.
基金the postdoctoral research grant received from the University of Glasgow for the partial financial support for this research work。
文摘This paper introduces damping amplifier friction vibration absorbers(DAFVAs),compound damping amplifier friction vibration absorbers(CDAFVAs),nested damping amplifier friction vibration absorbers(NDAFVAs),and levered damping amplifier friction vibration absorbers(LDAFVAs)for controlling the structural vibrations and addressing the limitations of conventional tuned mass dampers(TMDs)and frictiontuned mass dampers(FTMDs).The closed-form analytical solution for the optimized design parameters is obtained using the H_(2)and H_(∞)optimization approaches.The efficiency of the recently established closed-form equations for the optimal design parameters is confirmed by the analytical examination.The closed form formulas for the dynamic responses of the main structure and the vibration absorbers are derived using the transfer matrix formulations.The foundation is provided by the harmonic and random-white noise excitations.Moreover,the effectiveness of the innovative dampers has been validated through numerical analysis.The optimal DAFVAs,CDAFVAs,NDAFVAs,and LDAFVAs exhibit at least 30%lower vibration reduction capacity compared with the optimal TMD.To demonstrate the effectiveness of the damping amplification mechanism,the novel absorbers are compared with a conventional FTMD.The results show that the optimized novel absorbers achieve at least 91%greater vibration reduction than the FTMD.These results show how the suggested designs might strengthen the structure's resilience to dynamic loads.
基金The Scientific Research Foundation of the Third Institute of Oceanography,Ministry of Natural Resources under contract Nos 2020014 and 2020017the National Natural Science Foundation of China under contract No.41977211the National Program on Global Change and Air-Sea Interaction under contract No.GASI-02-SCS-YDsum。
文摘Petroleum hydrocarbon pollution is a global concern,particularly in coastal environments.Polycyclic aromatic hydrocarbons(PAHs) are regarded as the most toxic components of petroleum hydrocarbons.In this study,the biomonitoring and ranking effects of petroleum hydrocarbons and PAHs on the marine fish model Oryzias melastigma embryos were determined in the Jiulong River Estuary(JRE) and its adjacent waters in China.The results showed that the levels of petroleum hydrocarbons from almost all sites met the primary standard for marine seawater quality,and the concentrations of the 16 priority PAHs in the surface seawater were lower compared with those in other coastal areas worldwide.A new fish expert system based on the embryotoxicity of O.melastigma(OME-FES) was developed and applied in the field to evaluate the biological effects of petroleum hydrocarbons and PAHs.The selected physiological index and molecular indicators in OME-FES were appropriate biomarkers for indicating the harmful effects of petroleum hydrocarbons and PAHs.The outcome of OME-FES revealed that the biological effect levels of the sampling sites ranged from level Ⅰ(no stress) to level Ⅲ(medium stress),which is further corroborated by the findings of nested analysis of variance(ANOVA) models.Our results suggest that the OME-FES is an effective tool for evaluating and ranking the biological effects of marine petroleum hydrocarbons and PAHs.This method may also be applied to evaluate other marine pollutants based on its framework.
基金supported by National Key R&D Program of China (2022YFF0709101)China National Space Administration (D050104)National Natural Science Foundation of China (62105244 and U2030111)。
文摘The Hot Universe Baryon Surveyor (HUBS) mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution. In this paper, we report the latest progress in the design and construction of nested X-ray telescopes which were designed to use a three-stage conic-approximation type assembly to simplify the manufacturing process. The mirror substrate is made using the thermal glass slumping method, with mirrors characterized by a root-mean-square roughness of 0.3 nm, with expected high reflectivity and good thermal stability. We also discuss methods of telescope construction and conduct a deformation analysis of the manufactured mirror. The in situ measurement system program is developed to guide the telescope assembly process.
