Differences in time until dispersal between cryptic species of a marine nematode species complex

Co-occurrence of closely related species may be achieved in environments with fluctuating dynamics, where competitively inferior species can avoid competition through dispersal. Here we present an experiment in which we compared active dispersal abilities (time until first dispersal, number and gender of dispersive adults, and nematode densities at time of dispersal) in Litoditis marina, a common bacterivorous nematode species complex comprising four often co-occurring cryptic species, Pm I, II, III, and IV, as a function of salinity and food distribution. The experiment was conducted in microcosms consisting of an inoculation plate, connection tube, and dispersal plate. Results show species-specific dispersal abilities with Pm I dispersing almost one week later than Pm III. The number of dispersive adults at time of first dispersal was species-specific, with one dispersive female in Pm I and Pm III and a higher, gender-balanced, number in Pm II and Pm IV. Food distribution affected dispersal: in absence of food in the inoculation plate, all species dispersed after ca four days. When food was available Pm I dispersed later, and at the same time and densities irrespective of food conditions in the dispersal plate (food vs no food), suggesting density-dependent dispersal. Pm III dispersed faster and at a lower population density. Salinity affected dispersal, with slower dispersal at higher salinity. These results suggest that active dispersal in Litoditis marina is common, density-dependent, and with species, gender- and environment-specific dispersal abilities. These differences can lead to differential responses under suboptimal conditions and may help to explain temporary coexistence at local scales

To stay or go: differential dispersal rates in cryptic species of a marine nematode

Behind the morphological similarity of many species, a hidden genetic diversity can be found. This cryptic diversity has been well documented in the marine nematode Rhabditis (Pellioditis) marina, a common bactivore associated with decomposing macro-algae in the littoral zone of coastal and estuarine environments. Four cryptic species of R. marina (Pm I, Pm II, Pm III and Pm IV) co-occur along the south-western coast and estuaries of The Netherlands. This coexistence challenges traditional competition theory, which states that competition will be most severe between closely related species. A previous study showed that competition between the four cryptic species occurred, but interspecific interactions were affected by environmental conditions such as salinity. One of the most important mechanisms to react to competition is dispersal. Most organisms have at least one stage in which dispersal occurs over a specific spatial scale. Meiobenthic species, however, lack any pelagic stage. But, recent research shows more and more evidence that meiofauna is also able to actively disperse with lateral sinusoidal movements in the interstitial spaces as one of the most common modes of dispersal of nematodes over short distances. Dispersal is a process triggered partially by the internal conditions of organisms and partially by environmental conditions. In the current experiment, species-specific differences in active dispersal rates and the effects of salinity and food distribution on dispersal behaviour were tested in four cryptic species of R. marina (Pm I, Pm II, Pm III and Pm IV), The results of the experiment showed that dispersal is a species-specific behaviour with Pm III being the most rapid disperser (first dispersal event occurred after an average of 3 days), and Pm I the slowest disperser (average of 10 days). An effect of food distribution on the dispersal rates of all cryptic species was found with the most rapid dispersal if no food was present at the start situation. Salinity also had an effect with a higher dispersal rate at lower salinity for all the species. Moreover, the number of dispersive organisms differed between the species, with only one female disperser in Pm I and Pm III and a mix of female and male dispersers for Pm II and Pm IV at the first dispersal event. This species-specific dispersal behaviour and the influence of external conditions on dispersal can influence the reaction on competition. In a future experiment the effect of competition on dispersal will be studied by using competition cultures, where all four cryptic species can influence each other, but the organisms have the chance to disperse away. These results are important to better understand the processes behind the coexistence of cryptic species

Highly calcareous lacustrine soils in the Great Konya Basin, Turkey

The Great Konya Basin is in the south of the Central Anatolian Plateau in Turkey. It is a depression without outlet to the sea. The central part of the Basin is the floor of a former Pleistocene lake, the Ancient Konya Lake. This area, called the LacustrinePlain, has highly calcareous clayey sediments and is flat and level, except for ancient shorelines which form sandy ridges and beaches. Its soils have been studied in the summers of 1964-8 as part of the Konya Project, a research and training programme of the Department of Tropical Soil Science of the Agricultural University, Wageningen. This book is the last publication about the results in a series of five.The Quarternary history of the Lacustrine Plain, as regards sedimentation, was reconstructed with the help of existing climatic chronologies and with observations on geomorphology, soils, shells and pollen. Presumably Ancient Konya Lake, which had a constant level of about 1017 m, dried up in Postpluvial I (about 16.000 BC) and four smaller lakes or marshes existed in secondary depressions during Sub-pluvial I (about 9000 BC) which gradually disappeared. Their level varied between 1000 and 1006 m.The soils of the Lacustrine Plain were mostly formed in white uniform carbonatic clay, but differ markedly in composition and morphology because of past and present differences in hydrology, topography and vegetation. The soils have been studied and mapped on a regional basis and divided into Steppe Marl Soils, Marsh Marl Soils and Playa Marl Soils. The last group occurs north and east of Karapinar and is strongly salt- affected. Profile data of some 13 representative Marl Soil profiles are presented in the form of structural diagrams and tables for easy reference.Soil peels (preserved natural soil profiles) of the same representative soils are also used for a precise description of the pedological features and voids of the soil material, using Brewer's system of 'pedography'. Areas for more expensive thin sections could be selected more carefully. Interpretation is based on the descriptions in the field, in the soil peel and occasionally in thin section. Organisms, presumably mainly earthworms, seemed the main cause of the present structure of the solum. The effects of recent cultivation and irrigation are also demonstrated. Redistribution of carbonates humus and iron is observed and explained.The textural and mineralogical composition of Marl Soils was studied superficially. The soil texture without removal of carbonates is mostly clay to silty-clay and is slightly finer- textured after carbonates have been removed. The carbonates (mainly calcium carbonate as calcite) occupy about an equal proportion of the clay, silt and sand fractions. Clay minerals of the smectite group are commonest and palygorskite is present.The carbonatic clayey parent material of the Marl Soil is a sediment of about 60% mainly chemically precipitated calcite, debris from limestone and shells and the rest is a residue of non-calcareous clay minerals of residual and alluvial origin and sand sized mineral grains of alluvial or aeolian origin.The productivity of Steppe Marl Soils is estimated, using results from the soil peels and data on moisture and soil fertility. The suitability for agriculture is estimated by an existing procedure, which was refined and adapted to the area. The procedure compares estimated deficiencies in soil structure, soil moisture and chemical soil fertility in comparison with ideal conditions. The feasibility for improvement is then assessed for three management systems: dry farming without fertilizers, dry far ing with fertilizers and irrigated farming with fertilizers. The soil suitability in 4 classes (good, fair, restricted and unsuitable) is assessed on the basis of the above analysis. The suitability of Steppe Marl Soils for agriculture is judged as 'unsuitable' or 'restricted' under the dry-farming systems, mainly because of lack of moisture and 'restricted' under irrigation (mainly because of poor irrigability and poor response to fertilizers). It may become 'fair' under highly sophisticated irrigational management as is demonstrated on comparable soils in Israel and Florida

Black Dialect in Children\u27s Books

Black non-Standard English is different in grammar (syntax) from Standard English. The advent of the 60\u27s produced authors who explored the full possibilities of language to deal with their themes. The increased use of dialect by black authors, particularly children\u27s authors, was a sign that the nature of the black experience as they wanted to convey it did not have to rely on traditional forms, and literary devices; that they could treat familiar, realistic ideas and situations using a familiar dialect and relate that idea more effectively

Integrated modeling of friction stir welding of 6xxx series Al alloys: Process, microstructure and properties

International audienceCompared to most thermomechanical processing methods, friction stir welding (FSW) is a recent technique which has not yet reached full maturity. Nevertheless, owing to multiple intrinsic advantages, FSW has already replaced conventional welding methods in a variety of industrial applications especially for Al alloys. This provides the impetus for developing a methodology towards optimization, from process to performances, using the most advanced approach available in materials science and thermomechanics. The aim is to obtain a guidance both for process fine tuning and for alloy design. Integrated modeling constitutes a way to accelerate the insertion of the process, especially regarding difficult applications where for instance ductility, fracture toughness, fatigue and/or stress corrosion cracking are key issues. Hence, an integrated modeling framework devoted to the FSW of 6xxx series Al alloys has been established and applied to the 6005A and 6056 alloys. The suite of models involves an in-process temperature evolution model, a microstructure evolution model with an extension to heterogeneous precipitation, a microstructure based strength and strain hardening model, and a micro-mechanics based damage model. The presentation of each model is supplemented by the coverage of relevant recent literature. The "model chain" is assessed towards a wide range of experimental data. The final objective is to present routes for the optimization of the FSW process using both experiments and models. Now, this strategy goes well beyond the case of FSW, illustrating the potential of chain models to support a "material by design approach" from process to performances