Negative Covariance Research Articles

A negative covariation between toxoplasmosis and CoVID-19 with alternative interpretations

Coronaviruses may exert severely negative effects on the mortality and morbidity of birds and mammals including humans and domestic animals. Most recently CoVID-19 has killed about half million people (27th of June, 2020). Susceptibility to this disease appears to differ markedly across different societies but the factors underlying this variability are not known. Given that prevalence of toxoplasmosis in human societies may serve as a proxy for hygiene, and it also exerts both direct and immune-mediated antiviral effects, we hypothesize a negative covariation between toxoplasmosis and measures of the CoVID-19 pandemic across countries. We obtained aged-adjusted toxoplasmosis prevalence of pregnant women from the literature. Since the differences in the CoVID-19 morbidity and mortality may depend on the different timing of the epidemics in each country, we applied the date of first documented CoVID-19 in each country as a proxy of susceptibility, with a statistical control for population size effects. Using these two indices, we show a highly significant negative co-variation between the two pandemics across 86 countries. Then, considering that the wealth of nations often co-varies with the prevalence of diseases, we introduced GDP per capita into our model. The prevalence of toxoplasmosis co-varies negatively, while the date of first CoVID-19 co-varies positively with GDP per capita across countries. Further, to control for the strong spatial autocorrelation among countries, we carried out a Spatial Structure Analyses of the relationships between the date of first CoVID-19, prevalence of toxoplasmosis, and GDP per capita. Results of this analysis did not confirm a direct causal relationship between toxoplasmosis and susceptibility to the CoVID-19 pandemics. As far as an analysis of observational data let us to suggest, it appears that the interaction between CoVID-19 and toxoplasmosis is mediated by GDP per capita and spatial effects. This prompts the question whether the formerly known covariations of CoVID-19 and BCG vaccination or air pollution might have also emerged as spurious indirect effects.

Strategic Risk Shifting and the Idiosyncratic Volatility Puzzle: An Empirical Investigation

We find strong empirical support for the risk-shifting mechanism to account for the puzzling negative relation between idiosyncratic volatility and future stock returns. First, equity holders take on investments with high idiosyncratic risk when their firms are in distress and receive less monitoring from institutional holders as well as when the aggregate economy is in a bad state. Second, the strategically increased idiosyncratic volatility decreases equity betas, particularly in bad states when the market risk premium is high. The negative covariance between the equity beta and the market risk premium causes low and negative returns and alphas in firms with high idiosyncratic volatility. This paper was accepted by Tomasz Piskorski, finance.

Cerebrocerebellar structural covariance in temporal lobe epilepsy with hippocampal sclerosis

PurposeThe purpose of the study was to evaluate cerebral morphological changes in temporal lobe epilepsy with hippocampal sclerosis (TLE-HS) and their relationship to the cerebellum. MethodsThe study cohort included 21 patients with intractable TLE-HS (14 left-sided, 7 right-sided) and 38 healthy controls (HC). All patients later underwent anteromedial temporal lobe resection. All subjects were examined using a 1.5-T magnetic resonance imaging (MRI). Volumes of distinct cerebral and cerebellar structures were measured using voxel-based morphometry. The structural covariance of temporal lobe structures, insula, and thalamus with cerebellar substructures was examined using partial least squares regression. ResultsMorphological changes were more significant in the group with left TLE-HS when comparing left-sided with right-sided structures as well as when comparing patients with controls. The gray matter volume (GMV) of the temporal lobe structures was smaller ipsilaterally to the seizure onset side in most cases. There was a significant amygdala enlargement contralateral to the side of hippocampal sclerosis in both patients with right and left TLE-HS as compared with controls. Selected vermian structures in patients with left but not right TLE-HS had significantly larger GMV than the identical substructures in controls. The structural covariance differed significantly between patients with left and right TLE-HS as compared with HC. The analysis revealed significant negative covariance between anterior vermis and mesial temporal structures in the group with left TLE-HS. No significance was observed for the group with right TLE-HS. ConclusionThere is significant asymmetry in the GMV of cerebral and cerebellar structures in patients with TLE-HS. Morphological changes are distinctly more pronounced in patients with left TLE-HS.The observed structural covariance between the cerebellum and supratentorial structures in TLE-HS suggests associations beyond the mesial temporal lobe structures and thalamus.

Social Security Contributions and the Business Cycle

We investigate business cycle dynamics of social security contributions (SSC), by far the largest labor tax distortion in the OECD. In most countries, we find a negative covariation of SSC tax burdens with levels and growth of GDP at business cycle frequencies and lower. In detrended data, a decline of GDP of 1% is associated with a 0.05-0.2 percentage point increase in the aggregate SSC burden, measured as a fraction of the wage bill. For most countries, average marginal SSC rates exceed, but track average rates. Changes in average SSC tax burdens are largely due to adjustments in statutory tax schedules rather than cyclical shifts in earnings distributions. Our findings are consistent with Esping-Andersen's (1990) typology of social welfare states. In some countries, SSC rates co-move with measures of the “labor wedge” (Chari et al. 2007, Brinca et al. 2016).

Historical change of carbon burial in Late Quaternary sediments of the ancient Yellow River delta on the west coast of Bohai Bay, China

The ancient Yellow River Delta (YRD) on the west coast of the Bohai Bay is possibly a huge carbon sink due to the high runoff and sediment load of the Yellow River, which transfers huge amounts of particulate carbon from terrestrial sources to the Bohai Sea. In this study, a 30.76 m long core (BXZK11), drilled in 2016, has been analyzed for AMS 14C dating, grain size, foraminifera, organic carbon (OC), total nitrogen (TN), and stable carbon isotope ratios (δ13C) to provide insights into the historical changes of carbon burial in Late Quaternary sediments of the ancient YRD. The results show that the sedimentary environments are divided into six depositional units in core BXZK11. The biggest contributor to organic carbon apparent mass accumulation rate (OCAMAR) is the negative covariance between apparent sedimentation rate (ASR) and OC. The average of OCAMAR is 20.76 g/(m2 yr) during the Holocene. The rates are highest in delta front deposits and lowest in shallow sea environments. Compared with the modern YRD, BXZK11 exhibits rather low ASR and OCAMAR, indicative of the enormous variations of Yellow River sediment load into the sea and the significant difference of carbon sequestration capacity of YRD at different periods. C3 plants of the delta wetland gradually develop without C4 plant input as the delta transgresses after sea level stabilization. The sediments have been characterized by decreasing terrestrial organic matter (TOM) since 6500 cal. a BP, reflecting the decline of Yellow River freshwater discharge. Both the 8.2 ka event and the weak Asian monsoon summer event at 6265 cal. a BP correspond well with the low TOM in BXZK11. The implication is that climate may affect the dynamics of carbon burial by regulating terrestrial inputs.

Unusually homogeneous helium isotope composition of the Auckland Volcanic Field and its implications for the underlying mantle

The Auckland Volcanic Field (AVF) is one of the most intensively studied monogenetic basalt fields in the world yet its origin remains enigmatic. Magmatism in the AVF occurred from ~193 ka to 500 years bp. The trace element and isotopic diversity of AVF basalts require “small-scale” compositional heterogeneity in the underlying mantle that is comparable in volume to, or slightly larger than, the scale of individual eruptions in the AVF.Olivine from tephra and lava, representing the range of AVF compositions, was crushed and analysed for 3He/4He, and He and CO2 concentrations in an attempt to further characterize and explain the significance of the AVF “end-members”. AVF basalts show a negative covariation between the amount of CO2 released by crushing of olivine and the whole rock concentrations of highly incompatible trace elements, such as Ba, Rb, Nb, Zr, Ti and K. In contrast, the amount of He released by crushing shows no simple relations with the same incompatible elements or their ratios. This leads to a significant variation in CO2/3He ratios (9.4 × 107–3.5 × 109) that may relate to differences in magma ascent dynamics, as well as to different magma sources. The measured CO2/He ratios may have been influenced by varying amounts of CO2 diffusion into vapour bubbles within melt inclusions that depend on melt composition and magma ascent rate. However, petrographically there is no evidence for systematic differences in the size or quantity of vapour bubbles in olivine-hosted melt inclusions.3He/4He ratios in 14 AVF samples studied here show a narrow range from 6.57 to 7.26 RA (mean of 7.10 ± 0.26). This may imply a dominance of the mantle helium budget by small-scale heterogeneities. Alternatively, the 3He/4He results suggest that the tectonic and magmatic history of the mantle beneath the AVF has effectively hybridized the 3He/4He ratio to a larger extent than for highly incompatible trace element ratios and Pb-Nd-Sr isotopes. The value of ~7 RA for the mantle source of AVF basalts, in light of other evidence, suggests that there is a relatively homogeneous He isotope composition for the Zealandia-Antarctic mantle domain.

Recent immigrants alter the quantitative genetic architecture of paternity in song sparrows.

Quantifying additive genetic variances and cross‐sex covariances in reproductive traits, and identifying processes that shape and maintain such (co)variances, is central to understanding the evolutionary dynamics of reproductive systems. Gene flow resulting from among‐population dispersal could substantially alter additive genetic variances and covariances in key traits in recipient populations, thereby altering forms of sexual conflict, indirect selection, and evolutionary responses. However, the degree to which genes imported by immigrants do in fact affect quantitative genetic architectures of key reproductive traits and outcomes is rarely explicitly quantified. We applied structured quantitative genetic analyses to multiyear pedigree, pairing, and paternity data from free‐living song sparrows (Melospiza melodia) to quantify the differences in mean breeding values for major sex‐specific reproductive traits, specifically female extra‐pair reproduction and male paternity loss, between recent immigrants and the previously existing population. We thereby quantify effects of natural immigration on the means, variances, and cross‐sex covariance in total additive genetic values for extra‐pair paternity arising within the complex socially monogamous but genetically polygynandrous reproductive system. Recent immigrants had lower mean breeding values for male paternity loss, and somewhat lower values for female extra‐pair reproduction, than the local recipient population, and would therefore increase the emerging degree of reproductive fidelity of social pairings. Furthermore, immigration increased the variances in total additive genetic values for these traits, but decreased the magnitudes of the negative cross‐sex genetic covariation and correlation below those evident in the existing population. Immigration thereby increased the total additive genetic variance but could decrease the magnitude of indirect selection acting on sex‐specific contributions to paternity outcomes. These results demonstrate that dispersal and resulting immigration and gene flow can substantially affect quantitative genetic architectures of complex local reproductive systems, implying that comprehensive theoretical and empirical efforts to understand mating system dynamics will need to incorporate spatial population processes.

Multi-Sensor Combined Measurement While Drilling Based on the Improved Adaptive Fading Square Root Unscented Kalman Filter.

In the process of the attitude measurement for a steering drilling system, the measurement of the attitude parameters may be uncertain and unpredictable due to the influence of server vibration on bits. In order to eliminate the interference caused by vibration on the measurement and quickly obtain the accurate attitude parameters of the steering drilling tool, a new method for multi-sensor dynamic attitude combined measurement is presented. Firstly, by using a triaxial accelerometer and triaxial magnetometer measurement system, the nonlinear model based on the quaternion is established. Then, an improved adaptive fading square root unscented Kalman filter is proposed for eliminating the vibration disturbance signal. In this algorithm, the square root of the state covariance matrix is used to replace the covariance matrix in the classical unscented Kalman filter (UKF) to avoid the filter divergence caused by the negative definite state covariance matrix. The fading factor is introduced into UKF to adjust the filter gain in real-time and improve the adaptive ability of the algorithm to mutation state. Finally, the computational method of the fading factor is optimized to ensure the self-adaptability of the algorithm and reduce the computational complexity. The results of the laboratory test and the field-drilling data show that the proposed method can filter out the interference noise in the attitude measurement sensor effectively, improve the solution accuracy of attitude parameters of drilling tools in the case of abrupt changes in the measuring environment, and thus ensuring the dynamic stability of the well trajectory.

Realized Semibetas: Signs of Things to Come

We propose a new decomposition of the traditional market beta into four semibetas depending on the signed covariation between the market and individual asset returns. Consistent with the pricing implications from a mean-semivariance framework, we show that higher semibetas defined by negative market and negative (positive) asset return covariation predict significantly higher (lower) future returns, while the other two semibetas do not appear to be priced. The results are robust to an array of alternative test specifications and additional controls. Rather than betting on or against beta, we conclude that it is better to bet on and against the right semibetas.

Spatial covariation of fish population vital rates in a stream network

Animal populations are spatially structured in heterogeneous landscapes, in which local patches with differing vital rates are connected by dispersal of individuals to varying degrees. Although there is evidence that vital rates differ among local populations, much less is understood about how vital rates covary among local patches in spatially heterogeneous landscapes. In this study, we conducted a nine‐year annual mark–recapture survey to characterize spatial covariation of survival and growth for two Japanese native salmonids, white‐spotted charr Salvelinus leucomaenis japonicus and red‐spotted masu salmon Oncorhynchus masou ishikawae, in a headwater stream network composed of distinctly different tributary and mainstem habitats. Spatial structure of survival and growth differed by species and age class, but results provided support for negative covariation between vital rates, where survival was higher in the tributary habitat but growth was higher in the mainstem habitat. Thus, neither habitat was apparently more important than the other, and local habitats with complementary vital rates may make this spatially structured population less vulnerable to environmental change (i.e. portfolio effect). Despite the spatial structure of vital rates and possibilities that fish can exploit spatially distributed resources, movement of fish was limited due partly to a series of low‐head dams that prevented upstream movement of fish in the study area. This study shows that spatial structure of vital rates can be complex and depend on species and age class, and this knowledge is likely paramount to elucidating dynamics of spatially structured populations.

17 The Impact of Modifiable Comorbid Conditions on Long-term Patient Reported Outcomes in Burn Survivors

Abstract Introduction Pre-existing comorbidities in burn survivors increase the risk of death and negatively impact quality of life. Investigations to date have only evaluated comorbidities as cumulative indices, which prevents identification of specific conditions for risk reduction after injury. Therefore, we aimed to evaluate the differential effects of specific conditions on patient reported outcomes. Methods A prospectively maintained trauma registry was merged with a longitudinal burn database using unique patient identifiers for burn survivors from 2007–2018. Admission comorbidities included: chronic liver disease, diabetes, hypertension, chronic pulmonary disease, chronic gastrointestinal disease, malignancy, cerebrovascular accident, congestive heart failure, bleeding disorder, coagulopathy, congenital condition, psychiatric illness, major depressive disorder, smoking status, alcohol use disorder, substance use disorder, trauma history, and steroid use. Demographic and burn related variables included age, gender, race, surface area burned, and number of operations during admission. Health related quality of life was assessed using the Short Form-12/Veterans RAND 12(SF/VR-12©) health survey component scores at 6, 12, & 24 months post injury. SF/VR-12 outcomes were evaluated with generalized linear models. Results The dataset included 493 adult participants of which 354 were male (71.8%). Median burn size was 14% TBSA (IQR 5%, 28%), and mean age was 45.0±16.3 years. 343 participants (69.6%) had ≥1 comorbidity, with a mean of 1.32±1.30 comorbidities/participant. SF/VR-12 mental component scores at 6 and 12 months post injury were negatively associated with history of psychiatric illness (p< 0.001, p=0.013); there were no significant predictors at 24 month follow up. SF/VR-12 physical component scores were negatively associated with smoking (p=0.019), diabetes (p=0.001), alcohol use disorder (p=0.001), and history of CVA (p=0.005) at 6 month follow up. 12 month SF/VR-12 physical component scores were negatively associated with trauma history (p=0.001), diabetes (p=0.042), and CHF (p=0.016). 24-month SF/VR-12 physical component scores were negatively associated with psychiatric illness (p=0.003). Conclusions Smoking, alcohol use disorder, and diabetes were associated with lower physical component scores 6-months after injury; diabetes persisted a negative covariate at 12 months. Psychiatric illness was negatively associated with mental component scores at 6 and 12 months after injury. Burn survivors may benefit from integrated diabetes management and mental health treatment during their rehabilitation. Applicability of Research to Practice Specific comorbid conditions differentially affect quality of life in burn survivors. Targeting management of specific conditions during recovery may improve quality of life.

Variability scaling and consistency in airborne and satellite altimetry measurements of Arctic sea ice

Abstract. Satellite and airborne remote sensing provide complementary capabilities for the observation of the sea ice cover. However, due to the differences in footprint sizes and noise levels of the measurement techniques, as well as sea ice's variability across scales, it is challenging to carry out inter-comparison or consistently study these observations. In this study we focus on the remote sensing of sea ice thickness parameters and carry out the following: (1) the analysis of variability and its statistical scaling for typical parameters and (2) the consistency study between airborne and satellite measurements. By using collocating data between Operation IceBridge and CryoSat-2 (CS-2) in the Arctic, we show that consistency exists between the variability in radar freeboard estimations, although CryoSat-2 has higher noise levels. Specifically, we notice that the noise levels vary among different CryoSat-2 products, and for the European Space Agency (ESA) CryoSat-2 freeboard product the noise levels are at about 14 and 20 cm for first-year ice (FYI) and multi-year ice (MYI), respectively. On the other hand, for Operation IceBridge and NASA's Ice, Cloud, and land Elevation Satellite (ICESat), it is shown that the variability in snow (or total) freeboard is quantitatively comparable despite more than a 5-year time difference between the two datasets. Furthermore, by using Operation IceBridge data, we also find widespread negative covariance between ice freeboard and snow depth, which only manifests on small spatial scales (40 m for first-year ice and about 80 to 120 m for multi-year ice). This statistical relationship highlights that the snow cover reduces the overall topography of the ice cover. Besides this, there is prevalent positive covariability between snow depth and snow freeboard across a wide range of spatial scales. The variability and consistency analysis calls for more process-oriented observations and modeling activities to elucidate key processes governing snow–ice interaction and sea ice variability on various spatial scales. The statistical results can also be utilized in improving both radar and laser altimetry as well as the validation of sea ice and snow prognostic models.

Environmentally triggered variability in the genetic variance-covariance of herbivory resistance of an exotic plant Solidago altissima.

The variability in the genetic variance–covariance (G‐matrix) in plant resistance and its role in the evolution of invasive plants have been long overlooked. We conducted an additional analysis of the data of a reciprocal transplant experiment with tall goldenrod, Solidago altissima, in multiple garden sites within its native range (USA) and introduced range (Japan). We explored the differences in G‐matrix of resistance to two types of foliar herbivores: (a) a lace bug that is native to the USA and recently introduced to Japan, (b) and other herbivorous insects in response to plant origins and environments. A negative genetic covariance was found between plant resistances to lace bugs and other herbivorous insects, in all combinations of garden locations and plant origins except for US plants planted in US gardens. The G‐matrix of the resistance indices did not differ between US and Japanese plants either in US or Japanese gardens, while it differed between US and Japanese gardens in both US and Japanese plants. Our results suggested that the G‐matrix of the plant resistance may have changed in response to novel environmental differences including herbivore communities and/or other biotic and abiotic factors in the introduced range. This may have revealed a hidden trade‐off between resistances, masked by the environmental factors in the origin range. These results suggest that the stability of the genetic covariance during invasion, and the environmentally triggered variability in the G‐matrices of plant resistance may help to protect the plant against multiple herbivore species without changing its genetic architecture and that this may lead to a rapid adaptation of resistance in exotic plants. Local environments of the plant also have a critical effect on plant resistance and should be considered in order to understand trait evolution in exotic plants.

Single nucleotide polymorphism heritability and differential patterns of genetic overlap between inattention and four neurocognitive factors in youth.

Theoretical models of attention-deficit/hyperactivity disorder implicate neurocognitive dysfunction, yet neurocognitive functioning covers a range of abilities that may not all be linked with inattention. This study (a) investigated the single nucleotide polymorphism (SNP) heritability (h2SNP) of inattention and aspects of neurocognitive efficiency (memory, social cognition, executive function, and complex cognition) based on additive genome-wide effects; (b) examined if there were shared genetic effects among inattention and each aspect of neurocognitive efficiency; and (c) conducted an exploratory genome-wide association study to identify genetic regions associated with inattention. The sample included 3,563 participants of the Philadelphia Neurodevelopmental Cohort, a general population sample aged 8-21 years who completed the Penn Neurocognitive Battery. Data on inattention was obtained with the Kiddie Schedule of Affective Disorders (adapted). Genomic relatedness matrix restricted maximum likelihood was implemented in genome-wide complex trait analysis. Analyses revealed significant h2SNP for inattention (20%, SE = 0.08), social cognition (13%, SE = 0.08), memory (17%, SE = 0.08), executive function (25%, SE = 0.08), and complex cognition (24%, SE = 0.08). There was a positive genetic correlation (0.67, SE = 0.37) and a negative residual covariance (-0.23, SE = 0.06) between inattention and social cognition. No SNPs reached genome-wide significance for inattention. Results suggest specificity in genetic overlap among inattention and different aspects of neurocognitive efficiency.

Precautionary Savings and the Stock-Bond Covariance

I show that the precautionary savings motive can account for high-frequency variation in the stock-bond covariance. An increase in the price of risk lowers risky asset prices on account of an increase in risk premia; it lowers bond yields on account of the precautionary savings component. Consequently, a price of risk shock moves risky and safe asset prices in the opposite direction. Times when the price of risk is volatile see a more negative stock-bond covariance. I demonstrate that a model calibrated to match the equity risk premium fits well the recent evidence on stock-bond covariance. Empirically, I show that stock-bond covariance co-moves with credit spreads and can predict excess returns on risky bonds and on bond-like stocks. The calibrated model underlines the first-order effect of risk compensation on safe rates.

Pre- and post-copulatory traits working in concert: sexual dichromatism in passerines is associated with sperm morphology.

Passerine birds produce costly traits under intense sexual selection, including elaborate sexually dichromatic plumage and sperm morphologies, to compete for fertilizations. Plumage and sperm traits vary markedly among species, but it is unknown if this reflects a trade-off between pre- and post-copulatory investment under strong sexual selection producing negative trait covariance, or variation in the strength of sexual selection among species producing positive covariance. Using phylogenetic regression, we analysed datasets describing plumage and sperm morphological traits for 278 passerine species. We found a significant positive relationship between sperm midpiece length and male plumage elaboration and sexual dichromatism. We did not find a relationship between plumage elaboration and testes mass. Our results do not support a trade-off between plumage and sperm traits, but may be indicative of variance among species in the strength of sexual selection to produce both brightly coloured plumage and costly sperm traits.

Estimation of temporal covariances in pathogen dynamics using Bayesian multivariate autoregressive models.

It is well recognised that animal and plant pathogens form complex ecological communities of interacting organisms within their hosts, and there is growing interest in the health implications of such pathogen interactions. Although community ecology approaches have been used to identify pathogen interactions at the within-host scale, methodologies enabling robust identification of interactions from population-scale data such as that available from health authorities are lacking. To address this gap, we developed a statistical framework that jointly identifies interactions between multiple viruses from contemporaneous non-stationary infection time series. Our conceptual approach is derived from a Bayesian multivariate disease mapping framework. Importantly, our approach captures within- and between-year dependencies in infection risk while controlling for confounding factors such as seasonality, demographics and infection frequencies, allowing genuine pathogen interactions to be distinguished from simple correlations. We validated our framework using a broad range of synthetic data. We then applied it to diagnostic data available for five respiratory viruses co-circulating in a major urban population between 2005 and 2013: adenovirus, human coronavirus, human metapneumovirus, influenza B virus and respiratory syncytial virus. We found positive and negative covariances indicative of epidemiological interactions among specific virus pairs. This statistical framework enables a community ecology perspective to be applied to infectious disease epidemiology with important utility for public health planning and preparedness.

Adaptive Least-Squares Collocation Algorithm Considering Distance Scale Factor for GPS Crustal Velocity Field Fitting and Estimation

High-precision, high-reliability, and high-density GPS crustal velocity are extremely important requirements for geodynamic analysis. The least-squares collocation algorithm (LSC) has unique advantages over crustal movement models to overcome observation errors in GPS data and the sparseness and poor geometric distribution in GPS observations. However, traditional LSC algorithms often encounter negative covariance statistics, and thus, calculating statistical Gaussian covariance function based on the selected distance interval leads to inaccurate estimation of the correlation between the random signals. An unreliable Gaussian statistical covariance function also leads to inconsistency in observation noise and signal variance. In this study, we present an improved LSC algorithm that takes into account the combination of distance scale factor and adaptive adjustment to overcome these problems. The rationality and practicability of the new algorithm was verified by using GPS observations. Results show that the new algorithm introduces the distance scale factor, which effectively weakens the influence of systematic errors by improving the function model. The new algorithm can better reflect the characteristics of GPS crustal movement, which can provide valuable basic data for use in the analysis of regional tectonic dynamics using GPS observations.

Community assembly processes along a sub-Mediterranean elevation gradient: analyzing the interdependence of trait community weighted mean and functional diversity

Community-weighted mean (CWM) and functional diversity (FD) describe the two aspects of plant communities’ functional structure. While they have been often used separately to infer assembly processes, their covariation can actually provide useful insights into the prevalence of a particular assembly process over the other. We propose a framework where positive or negative covariation of these indices can be related to different assembly processes along an environmental gradient. We tested this framework in grassland communities along elevation gradient in Central Apennines by collecting species cover and traits of the most abundant species and calculating the effect size CWM and FD. We performed major axis regression for each effect size of CWM-FD relationship for different belts along the elevation gradient. The observation that Plant Height showed a positive CWM-FD relationship only under more stressful conditions indicates that there may be a tendency towards habitat filtering. Seed Mass showing positive covariation in each belt may indicate the presence of both habitat filtering and limiting similarity acting with different intensity depending on the environmental stress level. Negative covariation between CWM-Plant Height and Seed Mass-FD under less stress suggests biotic filter, while positive covariation between CWM-Plant Height and both Seed Mass and SLA FD under stressful conditions suggests the presence of habitat filtering. Ultimately, the relationship of CWM and FD may provide information on how different communities assemble along an environmental gradient. Moreover, combining the information of CWM with the FD and environmental stress level might help to identify the processes behind the same functional pattern.

Trader differences in Shanghai’s A-share and B-share markets: Effects on interaction with the Shanghai housing market

This study analyzes the relationship between the second-hand house price index of Shanghai and Shanghai stock market indices distinguishing between the A-share market, in which Chinese investors predominate, and the B-share market, in which foreign investors predominate. Monthly data for the period April 2003 to June 2018 are analyzed using VAR and GARCH methods. The A-share market shows little covariance with the housing market, whereas the B-share market generally shows a negative covariance, indicating the potential for B-shares to provide risk diversification for Shanghai house owners. Using VAR estimation, a positive shock to the housing market is found to have a negative effect on the A-share market contrary to a positive such credit-price effect between stocks and house prices established for developed countries, perhaps due to a crowding-out of rising house prices on share purchase. Using GARCH estimation, however, the negative credit-price effect is discerned to apply only for negative house price shocks, suggesting falling housing prices allow more funds to be diverted to the share market. While the A-share market shows causality in only one direction from house prices to share prices, causality between the B-share and housing markets is two-way. This is consistent with the less restricted B-share market affording better information transmission.