We introduce a novel framework for conceptualising, quantifying and unifying discordant patterns of species richness along geographical gradients. While not itself explicitly mechanistic, this approach offers a path towards understanding mechanisms. In this study, we focused on the diverse patterns of species richness on mountainsides. We conjectured that elevational range midpoints of species may be drawn towards a single midpoint attractor - a unimodal gradient of environmental favourability. The midpoint attractor interacts with geometric constraints imposed by sea level and the mountaintop to produce taxon-specific patterns of species richness. We developed a Bayesian simulation model to estimate the location and strength of the midpoint attractor from species occurrence data sampled along mountainsides. We also constructed midpoint predictor models to test whether environmental variables could directly account for the observed patterns of species range midpoints. We challenged these models with 16 elevational data sets, comprising 4500 species of insects, vertebrates and plants. The midpoint predictor models generally failed to predict the pattern of species midpoints. In contrast, the midpoint attractor model closely reproduced empirical spatial patterns of species richness and range midpoints. Gradients of environmental favourability, subject to geometric constraints, may parsimoniously account for elevational and other patterns of species richness.

• Klíčová slova
• Bayesian model, Biogeography, elevational gradients, geometric constraints, mid-domain effect, midpoint predictor model, stochastic model, truncated niche,
• MeSH
• Bayesova věta MeSH
• biodiverzita * MeSH
• biologické modely * MeSH
• ekosystém * MeSH
• fyziologie rostlin MeSH
• hmyz fyziologie   MeSH
• obratlovci fyziologie   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH

Intracellular and extracellular mechanical forces play a crucial role during tissue growth, modulating nuclear shape and function and resulting in complex collective cell behaviour. However, the mechanistic understanding of how the orientation, shape, symmetry and homogeneity of cells are affected by environmental geometry is still lacking. Here we investigate cooperative cell behaviour and patterns under geometric constraints created by topographically patterned substrates. We show how cells cooperatively adopt their geometry, shape, positioning of the nucleus and subsequent proliferation activity. Our findings indicate that geometric constraints induce significant squeezing of cells and nuclei, cytoskeleton reorganization, drastic condensation of chromatin resulting in a change in the cell proliferation rate and the anisotropic growth of cultures. Altogether, this work not only demonstrates complex non-trivial collective cellular responses to geometrical constraints but also provides a tentative explanation of the observed cell culture patterns grown on different topographically patterned substrates. These findings provide important fundamental knowledge, which could serve as a basis for better controlled tissue growth and cell-engineering applications.

• MeSH
• biologické modely * MeSH
• buněčné jádro fyziologie   ultrastruktura   MeSH
• buněčný převod mechanických signálů fyziologie   MeSH
• buňky Hep G2 MeSH
• lidé MeSH
• mezibuněčná komunikace fyziologie   MeSH
• počítačová simulace MeSH
• proliferace buněk fyziologie   MeSH
• velikost buňky * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: A crucial step in conserving biodiversity is to identify the distributions of threatened species and the factors associated with species threat status. In the biodiversity hotspot of the Himalaya, very little is known about which locations harbour the highest diversity of threatened species and whether diversity of such species is related to area, mid-domain effects (MDE), range size, or human density. In this study, we assessed the drivers of variation in richness of threatened birds, mammals, reptiles, actinopterygii, and amphibians along an elevational gradient in Nepal Himalaya. RESULTS: Although geometric constraints (MDE), species range size, and human population density were significantly related to threatened species richness, the interaction between range size and human population density was of greater importance. Threatened species richness was positively associated with human population density and negatively associated with range size. CONCLUSIONS: In areas with high richness of threatened species, species ranges tend to be small. The preponderance of species at risk of extinction at low elevations in the subtropical biodiversity hotspot could be due to the double impact of smaller range sizes and higher human density.

• Klíčová slova
• Biodiversity conservation, Elevational gradient, Himalaya, Nepal, Threatened species,
• MeSH
• biodiverzita MeSH
• ekosystém * MeSH
• hustota populace MeSH
• lidé MeSH
• nadmořská výška * MeSH
• obratlovci fyziologie   MeSH
• ohrožené druhy * MeSH
• rozšíření zvířat * MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Nepál MeSH

Hedgehogs, as medium-sized plantigrade insectivores with low basal metabolic rates and related defensive anti-predator strategies, are quite sensitive to temperature and ecosystem productivity. Their ranges therefore changed dramatically due to Pleistocene climate oscillations, resulting in allopatric speciation and the subsequent formation of secondary contact zones. Such interactions between closely related species are known to generate strong evolutionary forces responsible for niche differentiation. In this connection, here, we detail the results of research on the phenotypic evolution in the two species of hedgehog present in central Europe, as based on genetics and geometric morphometrics in samples along a longitudinal transect that includes the contact zone between the species. While in allopatry, Erinaceus europaeus is found to have a larger skull than E. roumanicus and distinct cranial and mandibular shapes; the members of the two species in sympatry are smaller and more similar to each other, with a convergent shape of the mandible. The relevant data fail to reveal any major role for either hybridisation or clinal variation. We, therefore, hypothesise that competitive pressure exerted on the studied species does not generate divergent selection sufficient for divergent character displacement to evolve, instead giving rise to convergent selection in the face of resource limitation in the direction of smaller skull size. Considering the multi-factorial constraints present in the relevant adaptive landscape, reduction in size could also be facilitated by predator pressure in ecosystems characterised by mesopredator release and other anthropogenic factors. As the function of the animals' lower jaw is mainly connected with feeding (in contrast to the cranium whose functions are obviously more complex), we interpret the similarity in shape as reflecting local adaptations to overlapping dietary resources in the two species and hence as convergent character displacement.

• Klíčová slova
• Erinaceus, convergent character displacement, geometric morphometrics, species interactions,
• Publikační typ
• časopisecké články MeSH

Plant nuclear genome size (GS) varies over three orders of magnitude and is correlated with cell size and growth rate. We explore whether these relationships can be owing to geometrical scaling constraints. These would produce an isometric GS-cell volume relationship, with the GS-cell diameter relationship with the exponent of 1/3. In the GS-cell division relationship, duration of processes limited by membrane transport would scale at the 1/3 exponent, whereas those limited by metabolism would show no relationship. We tested these predictions by estimating scaling exponents from 11 published datasets on differentiated and meristematic cells in diploid herbaceous plants. We found scaling of GS-cell size to almost perfectly match the prediction. The scaling exponent of the relationship between GS and cell cycle duration did not match the prediction. However, this relationship consists of two components: (i) S phase duration, which depends on GS, and has the predicted 1/3 exponent, and (ii) a GS-independent threshold reflecting the duration of the G1 and G2 phases. The matches we found for the relationships between GS and both cell size and S phase duration are signatures of geometrical scaling. We propose that a similar approach can be used to examine GS effects at tissue and whole plant levels.

• MeSH
• biologické modely MeSH
• buněčné dělení MeSH
• buněčný cyklus * MeSH
• časové faktory MeSH
• délka genomu * MeSH
• diploidie MeSH
• genom rostlinný * MeSH
• rostlinné buňky fyziologie   MeSH
• rostliny genetika   MeSH
• velikost buňky * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The structures of 4-chloro-3-nitroaniline, C6H5ClN2O2, (I), and 4-iodo-3-nitroaniline, C6H5IN2O2, (II), are isomorphs and both undergo continuous (second order) phase transitions at 237 and 200 K, respectively. The structures, as well as their phase transitions, have been studied by single-crystal X-ray diffraction, Raman spectroscopy and difference scanning calorimetry experiments. Both high-temperature phases (293 K) show disorder of the nitro substituents, which are inclined towards the benzene-ring planes at two different orientations. In the low-temperature phases (120 K), both inclination angles are well maintained, while the disorder is removed. Concomitantly, the b axis doubles with respect to the room-temperature cell. Each of the low-temperature phases of (I) and (II) contains two pairs of independent molecules, where the molecules in each pair are related by noncrystallographic inversion centres. The molecules within each pair have the same absolute value of the inclination angle. The Flack parameter of the low-temperature phases is very close to 0.5, indicating inversion twinning. This can be envisaged as stacking faults in the low-temperature phases. It seems that competition between the primary amine-nitro N-H···O hydrogen bonds which form three-centred hydrogen bonds is the reason for the disorder of the nitro groups, as well as for the phase transition in both (I) and (II). The backbones of the structures are formed by N-H···N hydrogen bonding of moderate strength which results in the graph-set motif C(3). This graph-set motif forms a zigzag chain parallel to the monoclinic b axis and is maintained in both the high- and the low-temperature structures. The primary amine groups are pyramidal, with similar geometric values in all four determinations. The high-temperature phase of (II) has been described previously [Garden et al. (2004). Acta Cryst. C60, o328-o330].

• Klíčová slova
• 4-chloro-3-nitroaniline, 4-iodo-3-nitroaniline, Raman, crystal structure, geometric constraints, phase transitions,
• Publikační typ
• časopisecké články MeSH

DNA nanostructures (DNs) have gained popularity in various biomedical applications due to their unique properties, including structural programmability, ease of synthesis and functionalization, and low cytotoxicity. Effective utilization of DNs in biomedical applications requires a fundamental understanding of their interactions with living cells and the mechanics of cellular uptake. Current knowledge primarily focuses on how the physicochemical properties of DNs, such as mass, shape, size, and surface functionalization, affect uptake efficacy. However, the role of cellular mechanics and morphology in DN uptake remains largely unexplored. In this work, we show that cells subjected to geometric constraints remodel their actin cytoskeleton, resulting in differential mechanical force generation that facilitates DN uptake. The length, number, and orientation of F-actin fibers are influenced by these constraints, leading to distinct mechanophenotypes. Overall, DN uptake is governed by F-actin forces arising from filament reorganisation under geometric constraints. These results underscore the importance of actin dynamics in the cellular uptake of DNs and suggest that leveraging geometric constraints to induce specific cell morphology adaptations could enhance the uptake of therapeutically designed DNs.

• MeSH
• aktiny metabolismus   chemie   MeSH
• cytoskelet metabolismus   účinky léků   MeSH
• DNA * chemie   metabolismus   MeSH
• lidé MeSH
• mikrofilamenta metabolismus   účinky léků   MeSH
• nanostruktury * chemie   MeSH
• velikost částic MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• aktiny MeSH
• DNA * MeSH

The species-area relationship (SAR) is considered to be one of a few generalities in ecology, yet a universal model of its shape and slope has remained elusive. Recently, Harte et al. argued that the slope of the SAR for a given area is driven by a single parameter, the ratio between total number of individuals and number of species (i.e., the mean population size across species at a given scale). We provide a geometric interpretation of this dependence. At the same time, however, we show that this dependence cannot be universal across taxa: if it holds for a taxon composed from two subsets of species and also for one of its subsets, it cannot simultaneously hold for the other subset. Using three data sets, we show that the slope of the SAR considerably varies around the prediction. We estimate the limits of this variation by using geometric considerations, providing a theory based on species spatial turnover at different scales. We argue that the SAR cannot be strictly universal, but its slope at each particular scale varies within the constraints given by species' spatial turnover at finer spatial scales, and this variation is biologically informative.

• MeSH
• biodiverzita * MeSH
• biologické modely * MeSH
• demografie MeSH
• druhová specificita MeSH
• ekosystém MeSH
• ptáci * MeSH
• ryby * MeSH
• stromy * MeSH
• zeměpis MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Geografické názvy
• Česká republika MeSH
• Panama MeSH
• Středozemní moře MeSH

We report the first measurement of rapidity-odd directed flow (v_{1}) for D^{0} and D^{0}[over ¯] mesons at midrapidity (|y|<0.8) in Au+Au collisions at sqrt[s_{NN}]=200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. In 10-80% Au+Au collisions, the slope of the v_{1} rapidity dependence (dv_{1}/dy), averaged over D^{0} and D^{0}[over ¯] mesons, is -0.080±0.017(stat)±0.016(syst) for transverse momentum p_{T} above 1.5 GeV/c. The absolute value of D^{0} meson dv_{1}/dy is about 25 times larger than that for charged kaons, with 3.4σ significance. These data give a unique insight into the initial tilt of the produced matter, and offer constraints on the geometric and transport parameters of the hot QCD medium created in relativistic heavy-ion collisions.

• Publikační typ
• časopisecké články MeSH

Encapsulation of lithium in the confined spaces within individual nanocapsules is intriguing and highly desirable for developing high-performance Li metal anodes. This work aims for a mechanistic understanding of Li encapsulation and its confined growth kinetics inside 1D enclosed spaces. To achieve this, amorphous carbon nanotubes are employed as a model host using in situ transmission electron microscopy. The carbon shells have dual roles, providing geometric/mechanical constraints and electron/ion transport channels, which profoundly alter the Li growth patterns. Li growth/dissolution takes place via atom addition/removal at the free surfaces through Li+ diffusion along the shells in the electric field direction, resulting in the formation of unusual Li structures, such as poly-crystalline nanowires and free-standing 2D ultrathin (1-2 nm) Li membranes. Such confined front-growth processes are dominated by Li {110} or {200} growing faces, distinct from the root growth of single-crystal Li dendrites outside the nanotubes. Controlled experiments show that high lithiophilicity/permeability, enabled by sufficient nitrogen/oxygen doping or pre-lithiation, is critical for the stable encapsulation of lithium inside carbonaceous nanocapsules. First-principles-based calculations reveal that N/O doping can reduce the diffusion barrier for Li+ penetration, and facilitate Li filling driven by energy minimization associated with the formation of low-energy Li/C interfaces.

• Klíčová slova
• 2D Li crystals, Li encapsulation, amorphous carbon nanotubes, in situ TEM, lithium metal anodes, spatially confined growth,
• Publikační typ
• časopisecké články MeSH