How do load carriage and walking speed influence trunk coordination and stride parameters?

To determine the effects of load carriage and walking speed on stride parameters and the coordination of trunk movements, 12 subjects walked on a treadmill at a range of walking speeds (0.6-1.6 m s(-1)) with and without a backpack containing 40% of their body mass. It was hypothesized that compared to unloaded walking, load carriage decreases transverse pelvic and thoracic rotation, the mean relative phase between pelvic and thoracic rotations, and increases hip excursion. In addition, it was hypothesized that these changes would coincide with a decreased stride length and increased stride frequency. The findings supported the hypotheses. Dimensionless analyses indicated that there was a significantly larger contribution of hip excursion and smaller contribution of transverse plane pelvic rotation to increases in stride length during load carriage. In addition, there was a significant effect of load carriage on the amplitudes of transverse pelvic and thoracic rotation and the relative phase of pelvic and thoracic rotation. It was concluded that the shorter stride length and higher stride frequency observed when carrying a backpack is the result of decreased pelvic rotation. During unloaded walking, increases in pelvic rotation contribute to increases in stride length with increasing walking speed. The decreased pelvic rotation during load carriage requires an increased hip excursion to compensate. However, the increase in hip excursion is insufficient to fully compensate for the observed decrease in pelvis rotation, requiring an increase in stride frequency during load carriage to maintain a constant walking speed.     

How do belowground organisms influence plant-pollinator interactions?

Aims The majority of angiosperms are pollinated by animals, and this interaction is of enormous importance in both agricultural and natural systems. Pollinator behavior is influenced by plants' floral traits, and these traits may be modified by interactions with other community members. In recent years, knowledge of ecological linkages between above- and belowground organisms has grown tremendously. Soil communities are extremely diverse, and when their interactions with plants influence floral characteristics, they have the potential to alter pollinator attraction and visitation, but plant–pollinator interactions have been neglected in studies of the direct and indirect effects of soil organism–root interactions. Here, we review these belowground interactions, focusing on the effects of nitrogen-fixing bacteria, arbuscular mycorrhizal fungi and root-feeding herbivores, and their effects on floral traits and pollinators. Further, we identify gaps in our knowledge of these indirect effects and recommend promising directions and topics that should be addressed by future research.Important findings Belowground organisms can influence a wide variety of floral traits that are important mediators of pollinator attraction, including the number and size of flowers and nectar and pollen production. Other traits that are known to influence pollinators in some plant species, such as floral volatiles, color and nectar composition, have rarely or never been examined in the context of belowground plant interactions. Despite clear effects on flowers, relatively few studies have measured pollinator responses to belowground interactions. When these indirect effects have been studied, both arbuscular mycorrhizal fungi and root herbivores were found to shift pollinator visitation patterns. Depending on the interaction, these changes may either increase or decrease pollinator attraction. Finally, we discuss future directions for ecological studies that will more fully integrate belowground ecology with pollination biology. We advocate a multilevel approach to these questions to not only document indirect effect pathways between soil interactions and pollination but also identify the mechanisms driving changes in pollinator impacts and the resultant effects on plant fitness. A more thorough understanding of these indirect interactions will advance ecological theory and may inform management strategies in agriculture and conservation biology.     

How do social dominance and social information influence reproduction and the brain?

How does living in a social environment influence the brain? In particular, we ask the following questions: How do animals perceive and use social information? How does the perception of social information influence the reproductive system? Where is this represented in the brain? We present a model system in which these questions can be addressed, focusing on the brain's role in integrating information. In the social fish, Astatotilapia burtoni (Haplochromis), the relationship between social status and gonadotropin-releasing hormone (GnRH1) has been well established. Change in status results in numerous changes in the physiology of A. burtoni at every level of organization. Social status can regulate reproduction via the hypothalamic-pituitary-gonadal (HPG) axis. GnRH1 is used by the brain to signal the pituitary about reproductive state so reproductive control depends on regulation of this signaling peptide. In this fish, social dominance is tightly coupled to fertility. Here, we have exploited this link to understand the regulatory systems from circulating hormones, brain volume to gene expression.     

How does temporal variation in habitat connectivity influence metapopulation dynamics?

Metapopulation persistence depends on connectivity between habitat patches. While emphasis has been placed on the spatial dynamics of connectivity, much less has been placed on its short‐term temporal dynamics. In many terrestrial and aquatic ecosystems, however, transient (short‐term) changes in connectivity occur as habitat patches are connected and disconnected due, for example, to climatic or hydrological variability. We evaluated the implications of transient connectivity using a network‐based metapopulation model and a series of scenarios representing temporal changes in connectivity. The transient loss of connectivity can influence metapopulation persistence, and more strongly autocorrelated temporal dynamics affect metapopulation persistence more severely. Given that many ecosystems experience short‐term and temporary loss of habitat connectivity, it is important that these dynamics are adequately represented in metapopulation models; failing to do so may yield overly optimistic‐estimates of metapopulation persistence in fragmented landscapes.     

Are time delays always destabilizing? Revisiting the role of time delays and the Allee effect

One of the main challenges in ecology is to determine the cause of population fluctuations. Both theoretical and empirical studies suggest that delayed density dependence instigates cyclic behavior in many populations; however, underlying mechanisms through which this occurs are often difficult to determine and may vary within species. In this paper, we consider single species population dynamics affected by the Allee effect coupled with discrete time delay. We use two different mathematical formulations of the Allee effect and analyze (both analytically and numerically) the role of time delay in different feedback mechanisms such as competition and cooperation. The bifurcation value of the delay (that results in the Hopf bifurcation) as a function of the strength of the Allee effect is obtained analytically. Interestingly, depending on the chosen delayed mechanism, even a large time delay may not necessarily lead to instability. We also show that, in case the time delay affects positive feedback (such as cooperation), the population dynamics can lead to self-organized formation of intermediate quasi-stationary states. Finally, we discuss ecological implications of our findings.     

How much do valley fills influence headwater streams?

Valley fill mining has the potential to alter headwater stream habitat in many areas in the eastern United States. In valley fill mining, overburden is removed to expose underlying coal seams. The overburden is then deposited in the adjacent valley. The deposited overburden from mining increases sedimentation, increases stream conductivity, and alters hydrologic regimes downstream of the fill. Changes in downstream communities are not well documented. However, it was suspected the increased sedimentation and conductivity would have deleterious effects upon the downstream macroinvertebrate communities. In southern West Virginia, four pairs of streams, each consisting of a fill and a reference stream, were selected as representative of watersheds experiencing valley fill mining. Stream pairs were selected for similar environmental conditions, with one stream having a valley fill in its headwaters. Each stream was sampled by replicate Surber samples (n=9 per stream). Water chemistry and sediment measurements also were taken at each location. Valley fill streams experienced significantly higher specific conductance (p < 0.01), but did not have elevated levels of fine sediment. Fills exhibited elevated levels of Na, K, Mn, Mg, Ca, Ni and Fe relative to reference streams. Additionally, valley fill streams demonstrated significantly lower densities of Ephemeroptera, Coleoptera, Odonata, Non-insects, Scrapers, and Shredders (p < 0.03) than reference streams. Further, Ephemeroptera richness was negatively related to specific conductivity and many of the richness metrics were negatively related to metals, both of which were generally elevated in fill streams. It appears that at the minimum, valley fills increase specific conductance and metals in streams and this or some other unqualified factors structure the macroinvertebrate community downstream of the valley fill. However, given the level of disturbance in valley fills, it is surprising how little differences existed between fills and reference stream biota.     

How do tenascins influence the birth and life of a malignant cell?

Tenascins are large glycoproteins found in embryonic and adult extracellular matrices. Of the four family members, two have been shown to be overexpressed in the microenvironment of solid tumours: tenascin-C and tenascin-W. The regular presence of these proteins in tumours suggests a role in tumourigenesis, which has been investigated intensively for tenascin-C and recently for tenascin-W as well. In this review, we follow a malignant cell starting from its birth through its potential metastatic journey and describe how tenascin-C and tenascin-W contribute to these successive steps of tumourigenesis. We consider the importance of the mechanical aspect in tenascin signalling. Furthermore, we discuss studies describing tenascin-C as an important component of stem cell niches and present examples reporting its role in cancer therapy resistance.     

How do drought and fire influence the patterns of resprouting in Australian deserts?

Rainfall is the key driver of woody cover and life-history attributes in arid grassy biomes where disturbance is mostly rare and of low intensity. However, relatively little is known about the causes of woody community assembly in arid systems that are subject to periodic intense fire disturbance. In the central Australian desert region, grassland and shrubland fire can occur following above average rainfall. Patterns of species regeneration response (resprouting vs. reseeding) are poorly documented in this region. We tested the effects of rainfall and fire on species’ resprouting response across the latitudinal rainfall–fire gradient using constrained ordination of 385 sites and general linear models. A resprouting response was significantly greater in grassland habitat as well as at the high end of the rainfall–fire gradient. The frequency of epicormic stem resprouting also increased along the rainfall–fire gradient. We attribute this pattern to the combined effects of frequent fire and rapid gap closure on seedlings of slow-growing, fire-killed woody species in higher rainfall grasslands. In addition, we also demonstrated that rapidly maturing fire-recruiting species are similarly favoured by high fire disturbance. In arid grassy ecosystems, unlike in mesic savanna, flammable grassland supports a mix of resprouting and recruitment functional types, and habitat membership cannot be predicted by resprouting capacity. Regions, such as central Australia, that are characterised by grassland–shrubland mosaics of high and low fuel biomass, respectively, pose specific challenges to fire ecology research that are possibly best dealt with by focussing modelling at the habitat scale.     

How do neutrophils and pathogens interact?

Many pathogens can manipulate macrophages after phagocytosis yet are efficiently killed by neutrophils. This poses the question of whether neutrophils have mechanisms that enable them to specifically recognise pathogens and have pathogens evolved mechanisms to modulate neutrophil function? Here, we review recent work on neutrophils and their interaction with four different bacteria: Staphylococcus aureus, Helicobacter pylori, Anaplasma phagocytophilum and members of the Enterobacteriae family.     

How do generalist consumers coexist over evolutionary time? An explanation with nutrition and tradeoffs

Generalist consumers commonly coexist in many ecosystems. Yet, eco-evolutionary theory poses a problem with this observation: generalist consumers (usually) cannot coexist stably. To provide a solution to this theory-observation dissonance, we analyzed a simple eco-evolutionary consumer resource model. We modeled consumption of two nutritionally interactive resources by species which evolve their resource encounter rates subject to a tradeoff. As shown previously, consumers can ecologically coexist through tradeoffs in resource encounter rates; however, this coexistence is evolutionary unstable. Here, we find that nutritional interactions between resources and the shape of acquisition tradeoffs produce very similar evolutionary outcomes in isolation. Specifically, they produce evolutionarily stable communities composed either of two specialists (concave acquisition tradeoff or antagonistic nutrition) or a single generalist (convex acquisition tradeoff or complementary nutrition). Thus, the generalist-coexistence problem remains. However, the combination of nonlinear resource acquisition tradeoffs with nonlinear resource nutritional relationships creates selection forces that can push and pull against each other. Ultimately, this push-pull dynamic can stabilize the coexistence of two competing generalist consumers—but only when we coupled a convex acquisition tradeoff with antagonistic nutrition. Thus, our model here offers some resolution to the generalist-coexistence problem in eco-evolutionary, consumer-resource theory.     

Insect herbivory and ontogeny: How do growth and development influence feeding behaviour,morphology and host use?

Herbivorous insects exploit many different plants and plant parts and often adopt different feeding strategies throughout their life cycle. The conceptual framework for investigating insect–plant interactions relies heavily on explanations invoking plant chemistry, neglecting a suite of competing and interacting pressures that may also limit herbivory. In the present paper, the methods by which ontogeny, feeding strategies and morphological characters inhibit herbivory by mandibulate holometabolous insects are examined. The emphasis on mechanical disruption of plant cells in the insect digestive strategy changes the relative importance of plant ‘defences’, increasing the importance of leaf structure in inhibiting herbivory. Coupled with the implications of substantial morphological and behavioural changes in ontogeny, herbivores adopt a range of approaches to herbivory that are independent of plant chemistry alone. Many insect herbivores exhibit substantial ontogenetic character displacement in mandibular morphology. This is tightly correlated with changes in feeding strategy, with changes to the cutting edges of mandibles increasing the efficiency of feeding. The changes in feeding strategy are also characterized by changes in feeding behaviour, with many larvae feeding gregariously in early instars. Non‐nutritive hypotheses considering the importance of natural enemies, shelter‐building and thermoregulation may also be invoked to explain the ontogenetic consequences of changes to feeding behaviour. There is a need to integrate these factors into a framework considering the gamut of potential explanations of insect herbivory, recognizing that ontogenetic constraints are not only viable explanations but a logical starting point. The interrelations between ontogeny, size, morphology and behaviour highlight the complexity of insect–plant relationships. Given the many methods used by insect herbivores to overcome the challenges of consuming foliage, the need for species‐specific and stage‐ specific research investigating ontogeny and host use by insect herbivores is critical for developing general theories of insect–plant interactions.     

How do sex and sexual maturation influence the response of Monochamus galloprovincialis to host odours?

Finding the right host plant for feeding and reproduction is crucial for herbivorous insects. Usually they need both visual and olfactory cues to locate and colonize their host plants, but the respective role of the two types of stimuli is difficult to disentangle. Model plants mimicking the shape and colour of natural hosts, combined with odours dispensers, are relevant tools for this purpose. We used dummy pines and cut branches of natural pines to investigate host attraction in Monochamus galloprovincialis, the insect vector of the pine wood nematode in Europe. We compared the behavioural response of males and females, sexually mature or immature, in a large climatic chamber and in an olfactometer. Immature females were significantly attracted by the sole odours released by pines. Immature males and mature males and females needed a combination of visual and olfactory cues to find the host tree. These findings suggest that beetles use both visual and chemical cues to locate pine trees but that relevant stimuli likely differ between beetles of different sex and sexual maturation status. Our results question the implementation of precautionary clear‐cuts around infested trees for limiting the spread of PWN.     

How do changes in parental investment influence development in echinoid echinoderms?

SUMMARY Understanding the relationship between egg size, development time, and juvenile size is critical to explaining patterns of life-history evolution in marine invertebrates. Currently there is conflicting information about the effects of changes in egg size on the life histories of echinoid echinoderms. We sought to resolve this conflict by manipulating egg size and food level during the development of two planktotrophic echinoid echinoderms: the green sea urchin, Strongylocentrotus droebachiensis and the sand dollar, Echinarachnius parma . Based on comparative datasets, we predicted that decreasing food availability and egg size would increase development time and reduce juvenile size. To test our prediction, blastomere separations were performed in both species at the two-cell stage to reduce egg volume by 50%, producing whole- and half-size larvae that were reared to metamorphosis under high or low food levels. Upon settlement, age at metamorphosis, juvenile size, spine number, and spine length were measured. As predicted, reducing egg size and food availability significantly increased age at metamorphosis and reduced juvenile quality. Along with previous egg size manipulations in other echinoids, this study suggests that the relationship between egg size, development time, and juvenile size is strongly dependent upon the initial size of the egg.     

Does seasonality and pool connectivity influence fish trophic ecology in knickzone habitats?

Knickzones are large rock outcrops found in upstream and middle plateau river basins. This kind of geological formation, which is considered a macrohabitat, creates a complex of mesohabitats: pools, riffles and runs, with distinct characteristics. In the present work, the aim was to evaluate the influence of connectivity and seasonality on the trophic structure of the ichthyofauna found in knickzone pools. Fish were sampled in four connected and three isolated pools, during dry and rainy seasons, and the stomach contents of 20 species were analyzed. Seasonal differences in diet occurred, with greater contribution of algae and aquatic hexapod in the dry season and of plant fragments and organic matter in the rainy season. The high diet overlap found in the isolated pools may be related to more intensive biotic interactions among individuals confined in physically restricted habitats. Seasonality in combination with connectivity to the main channel influenced the trophic structure of fish assemblage in the knickzone. Knickzones dynamics are modulated by seasonal events, such as floods, and connectivity of habitats, being extremely important for the trophic interactions between species. Alterations to these dynamics, like the construction of hydroelectric power plants, can modify significantly the trophic ecology of knickzones.     

What are artificial neural networks and what they can do?

The artificial neural networks (ANN) are very often applied in many areas of toxicology for the solving of complex problems, such as the prediction of chemical compound properties and quantitative structure-activity relationship. The aim of this contribution is to give the basic knowledge about conception of ANN, theirs division and finally, the typical application of ANN will be discussed. Due to the diversity of architectures and adaptation algorithms, the ANNs are used in the broad spectrum of applications from the environmental processes modeling, through the optimization to quantitative structure-activity relationship (QSAR) methods. In addition, especially ANNs with Kohonen learning are very effective classification tool. The ANNs are mostly applied in cases, where the commonly used methods does not work.     

How do cyanobacteria sense and respond to light?

Cyanobacteria exhibit numerous responses to changes in the intensity and spectral quality of light. What sensors do cyanobacteria use to detect light and what are the mechanisms of signal transduction? The publication in 1996 of the complete genome sequence of the cyanobacterium Synechocystis 6803 provided a tremendous stimulus for research in this field, and many light‐sensors and signal transducers have now been identified. However, our knowledge of cyanobacterial light‐signal transduction remains fragmentary. This review summarizes what we know about the ways in which cyanobacteria perceive light, some of the ways which they respond to light signals and some recent achievements in elucidating the signal transduction mechanisms. Some problems in characterizing cyanobacterial signal transduction pathways are outlined and alternative experimental strategies are discussed.