The role of phytosiderophores in acquisition of iron and other micronutrients in graminaceous species: An ecological approach

Phytosiderophores (PS) are released in graminaceous species (Gramineae) under iron (Fe) and zinc (Zn) deficiency stress and are of great ecological significance for acquisition of Fe and presumably also of Zn. The potential for release of PS is much higher than reported up to now. Rapid microbial degradation during PS collection from nutrient solution-grown plants is the main cause of this underestimation. Due to spatial separation of PS release and microbial activity in the rhizosphere a much slower degradation of PS can be assumed in soil-grown plants. Concentrations of PS up to molar levels have been calculated under non-sterile conditions in the rhizosphere of Fe-deficient barley plants.Besides Fe, PS mobilize also Zn, Mn and Cu. Despite this unspecific mobilization, PS mobilize appreciable amounts of Fe in calcareous soils and are of significance for chlorosis resistance of graminaceous species. In most species the rate of PS release is high enough to satisfy the Fe demand for optimal growth on calcareous soils.In contrast to the chelates ZnPS and MnPS, FePS are preferentially taken up in comparison with other soluble Fe compounds. In addition, the specific uptake system for FePS (translocator) is regulated exclusively by the Fe nutritional status. Therefore, it seems appropriate to retain the term phytosiderophore instead of phytochelate.     

Gas exchange strategy in the Nile crocodile: a morphometric study

Summary The respiratory surface area (S_AR) per kilogram body mass (M_B), the harmonic mean thickness of the air-blood barrier (_htR) in the gas exchange tissue, and the anatomical diffusion factor (ADF=S_AR/_htR per M_B) were calculated for four juvenile Nile crocodiles. The ADF of three small specimens (mean M_B=3.59 kg) was 625 cm²·m^–1·kg^–1. The values varied considerably among individuals and were similar to that of a 5.68-kg specimen (593 cm²·m^–1·kg^–1). Only 9% of the ADF is located in the anterior third of the lung, which because of its conical shape makes up only 14 percent of the total lung volume. Particularly in the middle third of the lung, the proximal region near the intrapulmonary bronchus displays a greater ratio of respiratory/non-respiratory surface areas than do more distally located sampling sites. The _htR is also significantly smaller proximally than distally. The cumulative ADF per unit M_B is greater than that previously reported for this species on the basis of overall estimates of S_AR and _htR, but is still less than that of lizards and testudinids. The disposition of ADF between distal air storage region and the intrapulmonary bronchus is consistent with a bidirectional cross-current gas exchange model.Abbreviations ADF anatomical diffusion factor - %AR percent of S_A included in the effective respiratory zone - M _B body mass - NVP non-ventilatory period - %P percent of total lung volume containing parenchyma - S _A total surface area of intrapulmonary septa - S _ANR that portion ofS _A lying out the effective respiratory zone - S _V surface-to-volume ratio in the parenchyma - _htR harmonic mean thickness of the air-blood tissue barrier within the respiratory zone - V _P parenchymal volume - VP ventilatory period     

Multidimensional biases,gaps and uncertainties in global plant occurrence information

Plants are a hyperdiverse clade that plays a key role in maintaining ecological and evolutionary processes as well as human livelihoods. Biases, gaps and uncertainties in plant occurrence information remain a central problem in ecology and conservation, but these limitations remain largely unassessed globally. In this synthesis, we propose a conceptual framework for analysing gaps in information coverage, information uncertainties and biases in these metrics along taxonomic, geographical and temporal dimensions, and apply it to all c. 370 000 species of land plants. To this end, we integrated 120 million point‐occurrence records with independent databases on plant taxonomy, distributions and conservation status. We find that different data limitations are prevalent in each dimension. Different metrics of information coverage and uncertainty are largely uncorrelated, and reducing taxonomic, spatial or temporal uncertainty by filtering out records would usually come at great costs to coverage. In light of these multidimensional data limitations, we discuss prospects for global plant ecological and biogeographical research, monitoring and conservation and outline critical next steps towards more effective information usage and mobilisation. Our study provides an empirical baseline for evaluating and improving global floristic knowledge, along with a conceptual framework that can be applied to study other hyperdiverse clades.     

A habitat quality indicator for common birds in Europe based on species distribution models

The EU 2020 Biodiversity Strategy requires the gathering of information on biodiversity to aid in monitoring progress towards its main targets. Common species are good proxies for the diversity and integrity of ecosystems, since they are key elements of the biomass, structure, functioning of ecosystems, and therefore of the supply of ecosystem services. In this sense, we aimed to develop a spatially-explicit indicator of habitat quality (HQI) at European level based on the species included in the European Common Bird Index, also grouped into their major habitat types (farmland and forest). Using species occurrences from the European Breeding Birds Atlas (at 50 km × 50 km) and the maximum entropy algorithm, we derived species distribution maps using refined occurrence data based on species ecology. This allowed us to cope with the limitations arising from modelling common and widespread species, obtaining habitat suitability maps for each species at finer spatial resolution (10 km × 10 km grid), which provided higher model accuracy. Analysis of the spatial patterns of local and relative species richness (defined as the ratio between species richness in a given location and the average richness in the regional context) for the common birds analysed demonstrated that the development of a HQI based on species richness needs to account for the regional species pool in order to make objective comparisons between regions. In this way, we proved that relative species richness compensated for the bias caused by the inherent heterogeneous patterns of the species distributions that was yielding larger local species richness in areas where most of the target species have the core of their distribution range. The method presented in this study provides a robust and innovative indicator of habitat quality which can be used to make comparisons between regions at the European scale, and therefore potentially applied to measure progress towards the EU Biodiversity Strategy targets. Finally, since species distribution models are based on breeding birds, the HQI can be also interpreted as a measure of the capacity of ecosystems to provide and maintain nursery/reproductive habitats for terrestrial species, a key maintenance and regulation ecosystem service.     

Improving integrated management of weed control by determination of weed seed bank in sandy and clay soil

Knowledge of soil weed seed bank is important for population dynamics studied, establishment of appropriate weed management programs, a little effort in understanding weed seed bank can give valuable information about what weeds to expect in growing season, weed density, and when most weed germination will take place. In this study, a two - year''s, two sites were carried out with the aim of assessing weed seed bank status of the soil throughout 2018 and 2019. A site was worked out in Sakha Agriculture Research farm act as a clay soil, Kafr El-Sheikh Governorate, Agriculture Research Center (ARC). Another site was worked out in El-Ismailia Agr; Res; farm act as sandy soil, El-Ismailia Governorate, ARC. At each site, soil samples were selected from nine different places as like three Zigzag shapes divided into three, six and nine sites, “W” to act the whole soil area (30 faddan in Sakha farm, and 15 faddan in El-Ismailia farm). The soil samples were taken from topsoil 0–10 cm depth with an auger (core) 10 cm diameter the soils without tillage and before sowing the summer crop. The result of present the study in two different stations and soils, revealed that the number of soil samples to estimate weed seed banks should be either six or nine sites; each sample weighted 0.50 Kg soil with zigzag shape act a direct seed extraction technique to able recognize the abundance of weed species into the soil and their seed density. The aim is to improve integrated weed control.     

The socioecological complexity of ecological restoration in Mexico

Almost half of Mexican territory has been classified as environmentally degraded. The main response for the last 60 years has been reforestation to combat soil erosion and loss of forest cover, mostly carried out on private lands where negotiations with local stakeholders were critical. Despite four legal instruments referring to ecological restoration, no specific instrument that defines basic concepts, criteria and standards, required actions, or regulations to implement and evaluate ecological restoration exists. The Ministry of the Environment and Natural Resources is now solely in charge of restoration and only recently have external scientists been invited to be part of the process. Following important national and international events in Latin America and the Caribbean region, the First Mexican Symposium on Ecological Restoration was held in November, 2014. This historic event was the first action undertaken in Mexico to meet Objective 3 of the Global Strategy of Plant Conservation, coordinated in Mexico by the National Council for the Use and Knowledge of Biodiversity. Although mangrove ecosystems are the most endangered ecosystem type in Mexico, they were not well represented at the symposium. In contrast, several other ecosystem types, such as tropical dry forest and islands, have received increased attention. Overall, while the Symposium and above‐cited policy initiatives are important steps, Mexico needs to increase its institutional capacities and social organization of the rural sector with regard to ecological restoration. Better integration of social and natural scientists and increased participation of Mexico internationally is also needed.     

Assessing eutrophication in the Portuguese continental Exclusive Economic Zone within the European Marine Strategy Framework Directive

This study reports the state and causes of eutrophication in the Portuguese continental Exclusive Economic Zone (EEZ), during a 14-year period (1995–2008), following the European Marine Strategy Framework Directive (MSFD) and using the trophic index TRIX for an integrated evaluation of indicators of eutrophication, and identifies areas where monitoring is needed to improve the eutrophication assessment. A non-continuous dataset for the 8 indicators specified by the MSFD for eutrophication assessment was used, including published and grey data. Eutrophication indicators were validated and thresholds reviewed, considering regional differences. The diatom:flagellate ratio was found a poor indicator of eutrophication as shifts in the diatom:flagellate ratio naturally occur associated with alternating water column turbulence and upwelling, and stratification, and therefore, could not be associated with anthropogenic nutrient enrichment effects. Assessment areas were, as a whole, classified as non-problem areas concerning eutrophication. Although nutrient enrichment was observed in coastal waters, related to river plume influence, nutrient enrichment direct and indirect effects were generally not detectable, possibly due to water column dispersion and mixing processes. Only occasionally, mild eutrophication was found in specific areas under the influence of major river (Douro, Vouga and Guadiana) plumes, associated with high nutrient and phytoplankton biomass levels and seagrass decline, which indicates the need for directed monitoring on eutrophication in those areas.     

Measure dynamics on a one-dimensional continuous trait space: theoretical foundations for adaptive dynamics

The measure dynamics approach to modelling single-species coevolution with a one-dimensional trait space is developed and compared to more traditional methods of adaptive dynamics and the Maximum Principle. It is assumed that individual fitness results from pairwise interactions together with a background fitness that depends only on total population size. When fitness functions are quadratic in the real variables parameterizing the one-dimensional traits of interacting individuals, the following results are derived. It is shown that among monomorphisms (i.e. measures supported on a single trait value), the continuously stable strategy (CSS) characterize those that are Lyapunov stable and attract all initial measures supported in an interval containing this trait value. In the cases where adaptive dynamics predicts evolutionary branching, convergence to a dimorphism is established. Extensions of these results to general fitness functions and/or multi-dimensional trait space are discussed.     

Cooperation enhanced by the ‘survival of the fittest’ rule in prisoner's dilemma games on complex networks

Prevalence of cooperation within groups of selfish individuals is puzzling in that it contradicts with the basic premise of natural selection, whereby we introduce a model of strategy evolution taking place on evolving networks based on Darwinian ‘survival of the fittest’ rule. In the present work, players whose payoffs are below a certain threshold will be deleted and the same number of new nodes will be added to the network to maintain the constant system size. Furthermore, the networking effect is also studied via implementing simulations on four typical network structures. Numerical results show that cooperators can obtain the biggest boost if the elimination threshold is fine-tuned. Notably, this coevolutionary rule drives the initial networks to evolve into statistically stationary states with a broad-scale degree distribution. Our results may provide many more insights for understanding the coevolution of strategy and network topology under the mechanism of nature selection whereby superior individuals will prosper and inferior ones be eliminated.