Removal of signal peptide variants by cation exchange chromatography: A case study.

Signal peptide (SP) is required for secretion of recombinant proteins and typically cleaved by signal peptidase at its C-region to generate the mature proteins. Miscleavage of the SP is reported occasionally, resulting in a truncated- or elongated-terminal sequence. In the present work, we demonstrated that cation exchange (CEX) chromatography is an effective means for removing SP variants with a case study. With the selected resin/conditions, the chromatographic performance is comparable between runs performed at the low end and high end of load density and elution range. The procedure described in this work can be used as a general approach for resin selection and optimization of chromatographic conditions to remove byproducts that bind more strongly than the product to the selected resin.

Gradient conducting polymer surfaces with netrin-1-conjugation promote axon guidance and neuron transmission of human iPSC-derived retinal ganglion cells.

Major advances have been made in utilizing human-induced pluripotent stem cells (hiPSCs) for regenerative medicine. Nevertheless, the delivery and integration of hiPSCs into target tissues remain significant challenges, particularly in the context of retinal ganglion cell (RGC) restoration. In this study, we introduce a promising avenue for providing directional guidance to regenerated cells in the retina. First, we developed a technique for construction of gradient interfaces based on functionalized conductive polymers, which could be applied with various functionalized ehthylenedioxythiophene (EDOT) monomers. Using a tree-shaped channel encapsulated with a thin PDMS and a specially designed electrochemical chamber, gradient flow generation could be converted into a functionalized-PEDOT gradient film by cyclic voltammetry. The characteristics of the successfully fabricated gradient flow and surface were analyzed using fluorescent labels, time of flight secondary ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS). Remarkably, hiPSC-RGCs seeded on PEDOT exhibited improvements in neurite outgrowth, axon guidance and neuronal electrophysiology measurements. These results suggest that our novel gradient PEDOT may be used with hiPSC-based technologies as a potential biomedical engineering scaffold for functional restoration of RGCs in retinal degenerative diseases and optic neuropathies.

Development and validation of interpretable machine learning models to predict glomerular filtration rate in chronic kidney disease Colombian patients.

BACKGROUND: ML predictive models have shown their capability to improve risk prediction and assist medical decision-making, nevertheless, there is a lack of accuracy systems to early identify future rapid CKD progressors in Colombia and even in South America. OBJECTIVE: The purpose of this study was to develop a series of interpretable machine learning models that predict GFR at 6-months, 9-months, and 12-months. STUDY DESIGN AND SETTING: Over 29,000 CKD patients stage 1 to 3b (estimated GFR, <60 mL/min/1.73 m2) with an average of 3-year follow-up data were included. We used the machine learning extreme gradient boosting (XGBoost) to build three models to predict the next eGFR. Models were internally and externally validated. In addition, we included SHapley Additive exPlanation (SHAP) values to offer interpretable global and local prediction models. RESULTS: All models showed a good performance in development and external validation. However, the 6-months XGBoost prediction model showed the best performance in internal (MAE average = 6.07; RSME = 78.87), and in external validation (MAE average = 6.45, RSME = 18.94). The top 3 most influential features that pushed the predicted eGFR value to lower values were the interpolated values for eGFR and creatinine, and eGFR at baseline. CONCLUSION: In the current study we have developed and validated machine learning models to predict the next eGFR value at different intervals. Furthermore, we attempted to approach the need for prediction explanation by offering transparent predictions.

Topology-Driven Discovery of Transmembrane Protein S-Palmitoylation.

Protein S-palmitoylation is a reversible lipophilic posttranslational modification regulating a diverse number of signaling pathways. Within transmembrane proteins (TMPs), S-palmitoylation is implicated in conditions from inflammatory disorders to respiratory viral infections. Many small-scale experiments have observed S-palmitoylation at juxtamembrane Cys residues. However, most large-scale S-palmitoyl discovery efforts rely on trypsin-based proteomics within which hydrophobic juxtamembrane regions are likely underrepresented. Machine learning- by virtue of its freedom from experimental constraints - is particularly well suited to address this discovery gap surrounding TMP S-palmitoylation. Utilizing a UniProt-derived feature set, a gradient boosted machine learning tool (TopoPalmTree) was constructed and applied to a holdout dataset of viral S-palmitoylated proteins. Upon application to the mouse TMP proteome, 1591 putative S-palmitoyl sites (i.e. not listed in SwissPalm or UniProt) were identified. Two lung-expressed S-palmitoyl candidates (synaptobrevin Vamp5 and water channel Aquaporin-5) were experimentally assessed. Finally, TopoPalmTree was used for rational design of an S-palmitoyl site on KDEL-Receptor 2. This readily interpretable model aligns the innumerable small-scale experiments observing juxtamembrane S-palmitoylation into a proteomic tool for TMP S-palmitoyl discovery and design, thus facilitating future investigations of this important modification.

Prediction of poststroke independent walking using machine learning: a retrospective study.

BACKGROUND: Accurately predicting the walking independence of stroke patients is important. Our objective was to determine and compare the performance of logistic regression (LR) and three machine learning models (eXtreme Gradient Boosting (XGBoost), Support Vector Machines (SVM), and Random Forest (RF)) in predicting walking independence at discharge in stroke patients, as well as to explore the variables that predict prognosis. METHODS: 778 (80% for the training set and 20% for the test set) stroke patients admitted to China Rehabilitation Research Center between February 2020 and January 2023 were retrospectively included. The training set was used for training models. The test set was used to validate and compare the performance of the four models in terms of area under the curve (AUC), accuracy, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and F1 score. RESULTS: Among the three ML models, the AUC of the XGBoost model is significantly higher than that of the SVM and RF models (P < 0.001, P = 0.024, respectively). There was no significant difference in the AUCs between the XGBoost model and the LR model (0.891 vs. 0.880, P = 0.560). The XGBoost model demonstrated superior accuracy (87.82% vs. 86.54%), sensitivity (50.00% vs. 39.39%), PPV (73.68% vs. 73.33%), NPV (89.78% vs. 87.94%), and F1 score (59.57% vs. 51.16%), with only slightly lower specificity (96.09% vs. 96.88%). Together, the XGBoost model and the stepwise LR model identified age, FMA-LE at admission, FAC at admission, and lower limb spasticity as key factors influencing independent walking. CONCLUSION: Overall, the XGBoost model performed best in predicting independent walking after stroke. The XGBoost and LR models together confirm that age, admission FMA-LE, admission FAC, and lower extremity spasticity are the key factors influencing independent walking in stroke patients at hospital discharge. TRIAL REGISTRATION: Not applicable.

The influence of sample size and sampling design on estimating population-level intra specific trait variation (ITV) along environmental gradients.

Understanding the relationship between intraspecific trait variability (ITV) and its biotic and abiotic drivers is crucial for advancing population and community ecology. Despite its importance, there is a lack of guidance on how to effectively sample ITV and reduce bias in the resulting inferences. In this study, we explored how sample size affects the estimation of population-level ITV, and how the distribution of sample sizes along an environmental gradient (i.e., sampling design) impacts the probabilities of committing Type I and II errors. We investigated Type I and II error probabilities using four simulated scenarios which varied sampling design and the strength of the ITV-environment relationships. We also applied simulation scenarios to empirical data on populations of the small mammal, Peromyscus maniculatus across gradients of latitude and temperature at sites in the National Ecological Observatory Network (NEON) in the continental United States. We found that larger sample sizes reduce error rates in the estimation of population-level ITV for both in silico and Peromyscus maniculatus populations. Furthermore, the influence of sample size on detecting ITV-environment relationships depends on how sample sizes and population-level ITV are distributed along environmental gradients. High correlations between sample size and the environment result in greater Type I error, while weak ITV-environmental gradient relationships showed high Type II error probabilities. Therefore, having large sample sizes that are even across populations is the most robust sampling design for studying ITV-environment relationships. These findings shed light on the complex interplay among sample size, sampling design, ITV, and environmental gradients.

Investigating microstructural changes between in vivo and perfused ex vivo marmoset brains using oscillating gradient and b-tensor encoded diffusion MRI at 9.4 T.

PURPOSE: To investigate microstructural alterations induced by perfusion fixation in brain tissues using advanced diffusion MRI techniques and estimate their potential impact on the application of ex vivo models to in vivo microstructure. METHODS: We used oscillating gradient spin echo (OGSE) and b-tensor encoding diffusion MRI to examine in vivo and ex vivo microstructural differences in the marmoset brain. OGSE was used to shorten effective diffusion times, whereas b-tensor encoding allowed for the differentiation of isotropic and anisotropic kurtosis. Additionally, we performed Monte Carlo simulations to estimate the potential microstructural changes in the tissues. RESULTS: We report large changes (˜50%-60%) in kurtosis frequency dispersion (OGSE) and in both anisotropic and isotropic kurtosis (b-tensor encoding) after perfusion fixation. Structural MRI showed an average volume reduction of about 10%. Monte Carlo simulations indicated that these alterations could likely be attributed to extracellular fluid loss possibly combined with axon beading and increased dot compartment signal fraction. Little evidence was observed for reductions in axonal caliber. CONCLUSION: Our findings shed light on advanced MRI parameter changes that are induced by perfusion fixation and potential microstructural sources for these changes. This work also suggests that caution should be exercised when applying ex vivo models to infer in vivo tissue microstructure, as significant differences may arise.

[Predicting Ozone Concentration in Hangzhou with the Fusion Class Stacking Algorithm].

Aiming at the problem that the single machine learning model has low prediction accuracy of daily average ozone concentration, an ozone concentration prediction method based on the fusion class Stacking algorithm （FSOP） was proposed, which combined the statistical method ordinary least squares （OLS） with machine learning algorithms and improved the prediction accuracy of the ozone concentration prediction model by integrating the advantages of different learners. Based on the principle of the Stacking algorithm, the observation data of the daily maximum 8h ozone average concentration and meteorological reanalysis data in Hangzhou from January 2017 to December 2022 were used. Firstly, the specific ozone concentration prediction models based on the light gradient boosting machine （LightGBM） algorithm, long short-term memory model （LSTM）, and Informer model were established, respectively. Then, the prediction results of the above models were used as meta-features, and the OLS algorithm was used to obtain the prediction expression of ozone concentration to fit the observed ozone concentration. The results showed that the prediction accuracy of the model combined with the class Stacking algorithm was improved, and the fitting effect of ozone concentration was better. Among them, R2, RMSE, and MAE were 0.84, 19.65 µg·m-3, and 15.50 µg·m-3, respectively, which improved the prediction accuracy by approximately 8% compared with that of the single machine learning model.

Limited cerebellar gradient extension in temporal lobe epilepsy with dystonic posturing.

OBJECTIVE: Dystonic posturing (DP) is a common semiology in temporal lobe epilepsy (TLE). We aimed to explore cerebellar gradient alterations in functional connectivity in TLE patients with and without DP. METHODS: Resting-state functional MRI data were obtained in 60 TLE patients and 32 matched healthy controls. Patients were further divided into two groups: TLE with DP (TLE + DP, 31 patients) and TLE without DP (TLP-DP, 29 patients). We explored functional gradient alterations in the cerebellum based on cerebellar-cerebral functional connectivity and combined with independent component analysis to evaluate cerebellar-cerebral functional integration and reveal the contribution of the motor components to the gradient. RESULTS: There were no obvious differences in clinical features and postoperative seizure outcomes between TLE + DP and TLE-DP patients. Patients and controls all showed a clear unimodal-to-transmodal gradient transition in the cerebellum, while TLE patients demonstrated an extended principal gradient in functional connectivity compared to healthy controls, which was more limited in TLE + DP patients. Gradient alterations were more widespread in TLE-DP patients, involving bilateral cerebellum, while gradient alterations in TLE + DP patients were limited in the cerebellum ipsilateral to the seizure focus. In addition, more cerebellar motor components contributed to the gradient alterations in TLE + DP patients, mainly in ipsilateral cerebellum. SIGNIFICANCE: Extended cerebellar principal gradients in functional connectivity revealed excessive functional segregation between unimodal and transmodal systems in TLE. The functional connectivity gradients were more limited in TLE + DP patients. Functional connectivity in TLE patients with dystonic posturing involved more contribution of cerebellar motor function to ipsilateral cerebellar gradient. PLAIN LANGUAGE SUMMARY: Dystonic posturing contralateral to epileptic focus is a common symptom in temporal lobe epilepsy, and the cerebellum may be involved in its generation. In this study, we found cerebellar gradients alterations in functional connectivity in temporal lobe epilepsy patients with and without contralateral dystonic posturing. In particular, we found that TLE patients with dystonic posturing may have more limited cerebellar gradient in functional connectivity, involving more contribution of cerebellar motor function to ipsilateral cerebellar gradient. Our study suggests a close relationship between ipsilateral cerebellum and contralateral dystonic posturing.

Sprain energy consequences for damage localization and fracture mechanics.

The 2023 smooth Lagrangian Crack-Band Model (slCBM), inspired by the 2020 invention of the gap test, prevented spurious damage localization during fracture growth by introducing the second gradient of the displacement field vector, named the "sprain," as the localization limiter. The key idea was that, in the finite element implementation, the displacement vector and its gradient should be treated as independent fields with the lowest ([Formula: see text]) continuity, constrained by a second-order Lagrange multiplier tensor. Coupled with a realistic constitutive law for triaxial softening damage, such as microplane model M7, the known limitations of the classical Crack Band Model were eliminated. Here, we show that the slCBM closely reproduces the size effect revealed by the gap test at various crack-parallel stresses. To describe it, we present an approximate corrective formula, although a strong loading-path dependence limits its applicability. Except for the rare case of zero crack-parallel stresses, the fracture predictions of the line crack models (linear elastic fracture mechanics, phase-field, extended finite element method (XFEM), cohesive crack models) can be as much as 100% in error. We argue that the localization limiter concept must be extended by including the resistance to material rotation gradients. We also show that, without this resistance, the existing strain-gradient damage theories may predict a wrong fracture pattern and have, for Mode II and III fractures, a load capacity error as much as 55%. Finally, we argue that the crack-parallel stress effect must occur in all materials, ranging from concrete to atomistically sharp cracks in crystals.

Massively Enhanced Charge Selectivity, Ion Transport, and Osmotic Energy Conversion by Antiswelling Nanoconfined Hydrogels.

Developing a nanofluidic membrane with simultaneously enhanced ion selectivity and permeability for high-performance osmotic energy conversion has largely been unexplored. Here, we tackle this issue by the confinement of highly space-charged hydrogels within an orderedly aligned nanochannel array membrane. The nanoconfinement effect endows the hydrogel-based membrane with excellent antiswelling property. Furthermore, experimental and simulation results demonstrate that such a nanoconfined hydrogel membrane exhibits massively enhanced cation selectivity and ion transport properties. Consequently, an amazingly high power density up to ∼52.1 W/m2 with an unprecedented energy conversion efficiency of 37.5% can be reached by mixing simulated salt-lake water (5 M NaCl) and river water (0.01 M NaCl). Both efficiency indexes surpass those of most of the state-of-the-art nanofluidic membranes. This work offers insights into the design of highly ion-selective membranes to achieve ultrafast ion transport and high-performance osmotic energy harvesting.

Trans-Clot MAP gradient: A novel innovative technique during thrombectomy for acute ischemic stroke with potential applications for assessing collateral circulation, determining clot etiology, informing device selection, and predicting first-pass success.

Endovascular mechanical thrombectomy has significantly improved recovery in acute ischemic stroke (AIS). While traditional patient selection has relied on factors such as last known well and penumbra volume, emerging research highlights the importance of collateral circulation in influencing thrombectomy success. However, current methods to assess collateral circulation are often unreliable and lack standardization, limiting their integration into clinical decision-making and prompting the need for innovative approaches. This study introduces trans-clot manometry as a promising approach for quantitatively assessing collateral blood flow before thrombectomy. Two patients were included in this study: a 64-year-old female with a left M1 near-complete occlusion and an 81-year-old male with a left P1 occlusion. After receiving intravenous tenecteplase, each patient underwent emergent thrombectomy where intraoperative trans-clot manometry revealed significant trans-clot mean arterial pressure (MAP) gradients (66.7% for Patient 1 and 96.9% for Patient 2). Both patients had successful first-pass thrombectomy (Patient 1: TICI 3; Patient 2: TICI 3), with substantial clinical improvement (Patient 1: NIHSS 11 to 1; Patient 2: NIHSS 19 to 8). Intraoperative trans-clot manometry offers a simple yet powerful, objective, and generalizable measure of collateral circulation, applicable to a wide range of AIS cases regardless of clot location or vessel size. In addition, real-time correlations with heart-rate variability and radial artery pressures provide an intrinsic quality control, ensuring proper execution of the technique and accuracy of the resulting MAP gradient. Future research will focus on validating this approach, determining its generalizability, and establishing MAP gradient thresholds to enhance device selection and predict first-pass success.

High-latitude ocean habitats are a crucible of fish body shape diversification.

A decline in diversity from the equator to the poles is a common feature of Earth's biodiversity. Here, we examine body shape diversity in marine fishes across latitudes and explore the role of time and evolutionary rate in explaining the diversity gradient. Marine fishes' occupation of upper latitude environments has increased substantially over the last 80 million years. Fishes in the highest latitudes exhibit twice the rate of body shape evolution and one and a third times the disparity compared to equatorial latitudes. The faster evolution of body shape may be a response to increased ecological opportunity in polar and subpolar oceans due to (1) the evolution of antifreeze proteins allowing certain lineages to invade regions of cold water, (2) environmental disturbances driven by cyclical warming and cooling in high latitudes, and (3) rapid transitions across depth gradients. Our results add to growing evidence that evolutionary rates are often faster at temperate, not tropical, latitudes.

Effect of compound surface modification of shot peening and DLC coating on surface integrity and fatigue properties of gear steel 16Cr3NiWMoVNbE.

We conducted a study on the surface compound modification of shot peening and pure carbon DLC coating to simultaneously meet the requirements of wear resistance and fatigue resistance of spline structure. The effects of surface compound modification were investigated on the surface morphology, residual stress profile, microstructure, and nano-indentation hardness of 16Cr3NiWMovNbE gear steel, and conducted a comparative study on fatigue performance. The results show that the surface compound modification inherits the surface morphology and compressive residual stress gradient of shot peening, while the surface residual stress is slightly smaller than that of shot peening. In addition, surface compound modification still reflects the characteristics of high hardness and high fracture resistance of DLC coatings. Under the bending load based on spline tooth root, compared to the original specimen, the fatigue life after shot peening, pure carbon DLC coating, and surface compound modification is increased by 3.68, 2.35, and 3.36 respectively. Although the compound modified surface still maintains the shot peening morphology with a increasing surface roughness and stress concentration coefficient, the 100 µm-depth compressive residual stress profile and the subgrain refinement layer introduced, as well as the hard surface layer with good load-bearing capacity, have played the role of fatigue strengthening.

A Novel Echocardiographic Parameter to Confirm Low-Gradient Aortic Stenosis Severity.

Background: In patients with low-gradient (LG) aortic stenosis (AS), confirming disease severity and indication of intervention often requires dobutamine stress echocardiography (DSE) or aortic valve calcium scoring by computed tomography. We hypothesized that the mean transvalvular pressure gradient to effective orifice area ratio (MG/EOA, in mm Hg/cm2) measured during rest echocardiography identifies true-severe AS (TSAS) and is associated with clinical outcomes in patients with low-flow, LG-AS. Objectives: The purpose of this study was to evaluate the diagnostic and prognostic value of MG/EOA ratio. Methods: The diagnostic accuracy of MG/EOA ratio to identify TSAS was retrospectively assessed in: 1) an in vitro data set obtained in a circulatory model including 93 experimental conditions; and 2) an in vivo data set of 188 patients from the TOPAS (True or Pseudo-Severe Aortic Stenosis) study (NCT01835028). Receiver operating characteristic curves were used to assess the diagnostic accuracy of MG/EOA ratio for identifying TSAS, and Cox proportional hazards regression analyses were performed to assess its association with clinical outcomes. Results: The optimal cutoff of MG/EOA ratio to identify TSAS in patients with low-flow, LG-AS was ≥25 mm Hg/cm2 (correct classification 85%), as well as in vitro (100%). During a median follow-up of 1.41 ± 0.75 years, 146 (78%) patients met the composite endpoint of aortic valve replacement or all-cause mortality. A MG/EOA ratio ≥25 mm Hg/cm2 was independently associated with an increased risk of the composite endpoint (adjusted HR: 2.36 [95% CI: 1.63-3.42], P < 0.001). The Harell's C-index of MG/EOA was 0.68, equaling projected EOA (0.67) measured by DSE. Conclusions: MG/EOA ratio can be useful in low-flow, LG-AS to confirm AS severity and may complement DSE or aortic valve calcium scoring.

Elevational and temporal patterns of pollination success in distylous and homostylous buckwheats (Fagopyrum) in the Hengduan Mountains.

Reproductive strategies of sexually dimorphic plants vary in response to the environment. Here, we ask whether the sexual systems of Fagopyrum species (i.e., selfing homostylous and out-crossing distylous) represent distinct adaptive strategies to increase reproductive success in changing alpine environments. To answer this question, we determined how spatial and temporal factors (e.g., elevation and peak flowering time) affect reproductive success (i.e., stigmatic pollen load) in nine wild Fagopyrum species (seven distylous and two homostylous) among 28 populations along an elevation gradient of 1299-3315 m in the Hengduan Mountains, southwestern China. We also observed pollinators and conducted hundreds of hand pollinations to investigate inter/intra-morph compatibility, self-compatibility and pollen limitation in four Fagopyrum species (two distylous and two homostylous). We found that Fagopyrum species at higher elevation generally had bigger flowers and more stigmatic pollen loads; late-flowering individuals had smaller flowers and lower pollen deposition. Stigmatic pollen deposition was more variable in distylous species than in homostylous species. Although seed set was not pollen-limited in all species, we found that fruit set was much lower in distylous species, which rely on frequent pollinator visits, than in homostylous species capable of autonomous self-pollination. Our findings that pollination success increases at high elevations and decreases during the flowering season suggest that distylous and homostylous species have spatially and temporally distinct reproductive strategies related to environment-dependent pollinator activity.

Reprint: The Importance of Natural Acidified Systems in the Study of Ocean Acidification: What Have We Learned?

Human activity is generating an excess of atmospheric CO2, resulting in what we know as ocean acidification, which produces changes in marine ecosystems. Until recently, most of the research in this area had been done under small-scale, laboratory conditions, using few variables, few species and few life cycle stages. These limitations raise questions about the reproducibility of the environment and about the importance of indirect effects and synergies in the final results of these experiments. One way to address these experimental problems is by conducting studies in situ, in natural areas where expected future pH conditions already occur, such as CO2 vent systems. In the present work, we compile and discuss the latest research carried out in these natural laboratories, with the objective to summarize their advantages and disadvantages for research to improve these investigations so they can better help us understand how the oceans of the future will change.

Transjugular intrahepatic portosystemic shunt (TIPS) with variceal embolization reduces rebleeding risk for patients with portal pressure gradient over 12 mmHg: A long-term follow-up study.

OBJECTIVE: The consensus on whether Transjugular intrahepatic portosystemic shunt (TIPS) should be combined with variceal embolization in the treatment of portal hypertension-induced bleeding has not yet been reached. This study aimed to compare the difference in rebleeding incidence between TIPS and TIPS combined with variceal embolization and to analyze the optimal population for variceal embolization. METHODS: Clinical data of 721 patients undergoing TIPS were retrospectively collected. Patients were divided into two groups: TIPS alone (n = 155) and TIPS with embolization (TIPS+E, n = 251). Kaplan-Meier (KM) curves were used to analyze prognostic differences between the two groups, and subgroup analysis was conducted based on post-TIPS portal pressure gradient (PPG) exceeding 12 mmHg. RESULTS: After TIPS placement, the mean PPG significantly decreased for all patients. A total of 51 patients (12.6 %) experienced rebleeding, with 24 cases (15.9 %) in the TIPS group and 27 cases (10.6 %) in the TIPS+E group. There was no significant difference in cumulative rebleeding incidence between the TIPS+E and TIPS groups. In the subgroup with post-TIPS PPG greater than 12 mmHg, the cumulative rebleeding incidence was significantly lower in the TIPS+E group compared to the TIPS group (HR = 0.47, 95 %CI = 0.24-0.93, Log rank P = 0.026). No significant difference was found in patients with a post-TIPS PPG less than 12 mmHg. CONCLUSION: For patients with post-TIPS PPG exceeding 12 mmHg, simultaneous variceal embolization with TIPS placement significantly reduces the risk of rebleeding.

The mid-domain effect in flowering phenology.

The timing of flowering is an important driver of species distribution and community assembly patterns. However, we still have much to learn about the factors that shape flowering diversity (i.e., number of species flowering per period) in plant communities. One potential explanation of flowering diversity is the mid-domain effect, which states that geometric constraints on species ranges within a bounded domain (space or time) will yield a mid-domain peak in diversity regardless of ecological factors. Here, we determine whether the mid-domain effect explains peak flowering time (i.e., when most species of communities are flowering) across China. We used phenological data of 16,267 herbaceous and woody species from the provincial Flora in China and species distribution data from the Chinese Vascular Plant Distribution Database to determine relationships between the observed number of species flowering and the number of species flowering as predicted by the mid-domain effect model, as well as between three climatic variables (mean minimum monthly temperature, mean monthly precipitation, and mean monthly sunshine duration). We found that the mid-domain effect explained a significant proportion of the temporal variation in flowering diversity across all species in China. Further, the mid-domain effect explained a greater proportion of variance in flowering diversity at higher latitudes than at lower latitudes. The patterns of flowering diversity for both herbaceous and woody species were related to both the mid-domain effect and environmental variables. Our findings indicate that including geometric constraints in conjunction with abiotic and biotic predictors will improve predictions of flowering diversity patterns.

Strong evidence for latitudinal diversity gradient in mosses across the world.

Species richness generally decreases with increasing latitude, a biodiversity gradient that has long been considered as one of the few laws in ecology. This latitudinal diversity gradient has been observed in many major groups of organisms. In plants, the latitudinal diversity gradient has been observed in vascular plants, angiosperms, ferns, and liverworts. However, a conspicuous latitudinal diversity gradient in mosses at a global or continental scale has not been observed until now. Here, we analyze a comprehensive data set including moss species in each band of 20° in latitude worldwide. Our results show that moss species richness decreases strongly with increasing latitude, regardless of whether the globe is considered as a whole or different longitudinal segments (e.g., Old World versus New World) are considered separately. This result holds when variation in area size among latitudinal bands is taken into account. Pearson's correlation coefficient between latitude and species richness is -0.99 for both the Northern and Southern Hemispheres. Because bryophytes are an extant lineage of early land plants and because mosses not only include most of extant species of bryophytes but also are important constituents of most terrestrial ecosystems, understanding geographic patterns of mosses is particularly important. The finding of our study fills a critical knowledge gap.