How does scientific risk assessment of GM crops fit within the wider risk analysis?

The debate concerning genetically modified crops illustrates confusion between the role of scientists and that of wider society in regulatory decision making. We identify two fundamental misunderstandings, which, if rectified, would allow progress with confidence. First, scientific risk assessment needs to test well-defined hypotheses, not simply collect data. Second, risk assessments need to be placed in the wider context of risk analysis to enable the wider 'non-scientific' questions to be considered in regulatory decision making. Such integration and understanding is urgently required because the challenges to regulation will escalate as scientific progress advances.     

How does stochasticity in colonization accelerate the speed of invasion in a cellular automaton model?

We investigate the speed of invasion waves for a single species generated by stochastic short- and/or long-distance colonizations in a time-continuous cellular automaton (CA) model on a two-dimensional homogenous landscape. By simulating the CA models, we demonstrate that stochasticity can dramatically increase the speed of invasion compared to the corresponding deterministic CA model or the corresponding one-dimensional stochastic CA model. To explain this phenomenon, we first develop a mathematical model for the invasion involving only short-distance colonization (i.e., colonization only occurs from the eight adjacent cells), and present several approximation methods for solving the model. Our analyses show that the increased wave speed in the stochastic model is due to irregularity in the shape of the wavefront. Further extension of this model to include long-distance colonization demonstrates that stochasticity influences speeds to even greater extents in this case. Using dimension analysis, we deduced a semi-empirical formula for the speed as a function of three parameters intrinsic to short- and long-distance colonization, which agrees well with simulation results. Based on these results, we discuss how important stochasticity in colonization and spatial dimensionality are in the acceleration of invasion speed.     

How does imperviousness impact the urban rainfall-runoff process under various storm cases?

Dramatic changes in imperviousness exert significant influence on the rainfall-runoff process in urban catchments. In urban rainwater management, imperviousness is generally adopted as an effective indicator for assessing potential runoff risk. However, the effects of imperviousness on rainfall-runoff at the scale of small urbanized drainage areas have not been fully determined, particularly when various storm characteristics are considered. In this paper, a model-based analysis is conducted in a typical urban residential catchment in Beijing, China, in which 69 subareas are delineated within the catchment as the basic drainage units. Two metrics, total impervious area (TIA) and directly connected impervious area (DCIA), are employed to quantify the spatial characteristics of imperviousness of the subareas. Three runoff variables within the delineated subareas including total runoff depth (Q_t), peak runoff depth (Q_p), and lag time (T_lag) are simulated by using the Storm Water Management Model (SWMM) to represent the specific rainfall-runoff characteristics. Moreover, model input storms are designated to several typical flood-induced rainfall events with varying amounts, locations of rainfall peak, and durations for holistic assessment of imperviousness. Regression analyses are conducted to explore the contributions and relative significances of impervious metrics in predicting runoff variables under various storm cases. The results indicate that the performances of imperviousness with fine spatial scale (<1 ha) and heavy rainfall conditions (>34 mm) may vary markedly according to storm conditions. Specifically, TIA rather than DCIA acts as a dominate factor affecting total runoff, and its significance maintains relatively stable with various storm conditions. In addition, the combined use of both TIA and DCIA are more effective for predicting peak runoff than that using a single impervious metric; however, rainfall amount, peak location, and duration alter the contribution gaps between TIA and DCIA and the overall performance of the regression model. Moreover, DCIA is more likely to affect runoff lag time without the contribution of TIA; however, an increase in rainfall peak ratio or duration will significantly limit its performance. These results can provide insight into the hydrologic performance of imperviousness, which is essential for landscape design and runoff regulation in small urban catchments.     

Treating obesity: does antagonism of NPY fit the bill?

In this issue of Cell Metabolism, Erondu et al., (2006) identify a selective neuropeptide Y5 receptor antagonist that, as predicted from rodent studies, results in weight loss when administered to overweight and obese human subjects. In a one-year randomized placebo-controlled clinical trial, the weight loss was modest; the results support the emerging concept that NPY acts via overlapping and redundant energy homeostasis pathways.     

How does competition affect the transmission of information?

The use of social information is a prerequisite to the evolution of culture. In humans, social learning allows individuals to aggregate adaptive information and increase the complexity of technology at a level unparalleled in the animal kingdom. However, the potential to use social information is related to the availability of this type of information. Although most cultural evolution experiments assume that social learners are free to use social information, there are many examples of information withholding, particularly in ethnographic studies. In this experiment, we used a computer-based cultural game in which players were faced with a complex task and had the possibility to trade a specific part of their knowledge within their groups. The dynamics of information transmission were studied when competition was within- or exclusively between-groups. Our results show that between-group competition improved the transmission of information, increasing the amount and the quality of information. Further, informational access costs did not prevent social learners from performing better than individual learners, even when between-group competition was absent. Interestingly, between-group competition did not entirely eliminate access costs and did not improve the performance of players as compared with within-group competition. These results suggest that the field of cultural evolution would benefit from a better understanding of the factors that underlie the production and the sharing of information.     

How does mutation affect the distribution of phenotypes?

The potential for mutational processes to influence patterns of neutral or adaptive phenotypic evolution is not well understood. If mutations are directionally biased, shifting trait means in a particular direction, or if mutation generates more variance in some directions of multivariate trait space than others, mutation itself might be a source of bias in phenotypic evolution. Here, we use mutagenesis to investigate the affect of mutation on trait mean and (co)variances in zebrafish, Danio rerio. Mutation altered the relationship between age and both prolonged swimming speed and body shape. These observations suggest that mutational effects on ontogeny or aging have the potential to generate variance across the phenome. Mutations had a far greater effect in males than females, although whether this is a reflection of sex‐specific ontogeny or aging remains to be determined. In males, mutations generated positive covariance between swimming speed, size, and body shape suggesting the potential for mutation to affect the evolutionary covariation of these traits. Overall, our observations suggest that mutation does not generate equal variance in all directions of phenotypic space or in each sex, and that pervasive variation in ontogeny or aging within a cohort could affect the variation available to evolution.     

Exploring invasibility with species distribution modeling: How does fire promote cheatgrass (Bromus tectorum) invasion within lower montane forests?

Aim

Cheatgrass (Bromus tectorum) is notorious for creating positive feedbacks that facilitate vegetation type conversion within sagebrush steppe ecosystems in the western United States. Similar dynamics may exist in adjacent lower montane forest. However, fire‐forest‐cheatgrass dynamics have not been examined. We used species distribution modeling to answer three questions about fire and invasibility in lower montane forests: (Q1) Does fire create more suitable habitat for cheatgrass? (Q2) If so, which site attributes are altered to increase site suitability? (Q3) Does fire increase connectivity among suitable habitat and enhance spread?

Location

Shoshone National Forest, Wyoming, USA.

Methods

We measured cheatgrass presence–absence in 93 plots within Interior Douglas‐fir (Pseudotsuga menziesii var. glauca) forests. Random Forests predicted cheatgrass distribution with and without fire using nine site attributes: elevation, slope, aspect, solar radiation, annual precipitation, maximum temperature in July, minimum temperature in January, forest canopy cover and distance to nearest trail or road. Additionally, invasion pathways and spread were mapped using Circuitscape.

Results

Cheatgrass distribution was controlled by topographic and climate variables in the absence of fire. In particular, cheatgrass was most likely to occur at low elevation along dry, south‐ and east‐facing slopes. High‐severity fire increased potential cheatgrass distribution when forest canopy cover was reduced to below 30%. This process created new invasion pathways, which enhanced cheatgrass spread when modelled in Circuitscape.

Main conclusions

Our study showed that in the absence of fire, drier south‐ and east‐facing slopes at low elevation are most susceptible to cheatgrass invasion. However, high‐severity fire increased the total area susceptible to invasion—allowing cheatgrass to expand into previously unsuitable sites within lower montane forests in the western United States. These results are important for present day management and reflect that integrating responses to disturbance in species distribution models can be critical for making predictions about dynamically changing systems.

     

How does the presence of predators influence the persistence of antipredator behavior?

We developed a virtual world to study the effect of predators on predator recognition. We trained a neural network to discriminate between the shapes of simulated aerial and terrestrial predators and non-predators. Then, the network's weighting values were fixed into the genomes of a set of autonomous agents. These animats were required to eat, avoid death due to starvation, and avoid predation, by fleeing from approaching predators. We systematically varied the predator's lethality, the mutation rate, the cost of fleeing a predator, and the presence or absence of aerial and terrestrial predators. We used ANOVA to analyse the average recognition ability (a measure of directional selection) and the standard deviation of recognition ability (a measure of relaxed selection) after 500 generations of selection. Mutation rate and the cost of flight had the greatest effect on both the average and standard deviation of recognition abilities. The loss of all predators relaxed selection on predator recognition abilities. The loss of specific predators had complex effects on recognition abilities. Persistence is largely influenced by escape costs.     

How does poaching affect the size of national parks?

A variety of human activities have detrimental impacts on populations of species the park is designed to protect. These impacts range from direct hunting for trophy or subsistence needs, through vehicular collisions, to the direct loss of habitat due to forestry and agricultural activity. These impacts reduce the effective size of the parks and require changes in management policy that deal both with the direct cause of the problem and the underlying social conflicts that the presence of parks can place on humans in the surrounding communities. Recent studies from the Serengeti illustrate that increases in anti-poaching patrols increase the risk of poacher detection and lead to dramatic declines in levels of poaching. The economic arguments that support investment in anti-poaching patrols, rather than increased sentences for poachers who are caught, can be generalized to examine the costs and benefits of other changes in natural resource management that arise when attempting to manage the impact of anthropogenic activities in and around national parks.     

How much does the amphioxus genome represent the ancestor of chordates?

One of the main motivations to study amphioxus is its potential for understanding the last common ancestor of chordates, which notably gave rise to the vertebrates. An important feature in this respect is the slow evolutionary rate that seems to have characterized the cephalochordate lineage, making amphioxus an interesting proxy for the chordate ancestor, as well as a key lineage to include in comparative studies. Whereas slow evolution was first noticed at the phenotypic level, it has also been described at the genomic level. Here, we examine whether the amphioxus genome is indeed a good proxy for the genome of the chordate ancestor, with a focus on protein-coding genes. We investigate genome features, such as synteny, gene duplication and gene loss, and contrast the amphioxus genome with those of other deuterostomes that are used in comparative studies, such as Ciona, Oikopleura and urchin.     

How does the age of hoverfly females affect their reproduction?

In the present study, we observed the effect of age of Episyrphus balteatus DeGeer (Diptera, Syrphidae) females on their fecundity and fertility (number and percentage of fertile eggs). Eight newborn E. batteatus couples were placed in separated cages (30 cm x 30 cm x 60 cm) and the number of eggs laid and the egg viability were recorded daily during 45 days. E. balteatus females had a pre-oviposition period of 10 days before mating happened. The fecundity increased steadily from day 11 to day 16 with an average of 30 eggs a day. During the following days (from day 23 to day 45), we found that the optimal fecundity was observed every second day and that 70.47% of the eggs laid during the entire life of the females were fertile. We also found that the fertility decreased significantly when the females were older than 38 days. As result, the age of hoverfly females influence significantly on their reproduction, with suggesting that hoverfly females from 2 to 5 weeks old are important agents for biological control programs.     

How does arrestin respond to the phosphorylated state of rhodopsin?

Visual arrestin quenches light-induced signaling by binding to light-activated, phosphorylated rhodopsin (P-Rh*). Here we present structure-function data, which in conjunction with the refined crystal structure of arrestin (Hirsch, J. A., Schubert, C., Gurevich, V. V., and Sigler, P. B. (1999) Cell, in press), support a model for the conversion of a basal or "inactive" conformation of free arrestin to one that can bind to and inhibit the light activated receptor. The trigger for this transition is an interaction of the phosphorylated COOH-terminal segment of the receptor with arrestin that disrupts intramolecular interactions, including a hydrogen-bonded network of buried, charged side chains, referred to as the "polar core." This disruption permits structural adjustments that allow arrestin to bind to the receptor. Our mutational survey identifies residues in arrestin (Arg175, Asp30, Asp296, Asp303, Arg382), which when altered bypass the need for the interaction with the receptor's phosphopeptide, enabling arrestin to bind to activated, nonphosphorylated rhodopsin (Rh*). These mutational changes disrupt interactions and substructures which the crystallographic model and previous biochemical studies have shown are responsible for maintaining the inactive state. The molecular basis for these disruptions was confirmed by successfully introducing structure-based second site substitutions that restored the critical interactions. The nearly absolute conservation of the mutagenically sensitive residues throughout the arrestin family suggests that this mechanism is likely to be applicable to arrestin-mediated desensitization of most G-protein-coupled receptors.     

How does sucrose stabilize the native state of globular proteins?

It is well known that sucrose stabilizes the native state of globular proteins against both chemical denaturants and temperature. A largely accepted explanation of sucrose-induced stabilization is not yet emerged. It is shown that the same theoretical approach able to rationalize the occurrence of cold denaturation, the contrasting role of GdmCl and Gdm₂SO₄, and the TMAO counteraction of urea denaturing activity [PCCP 12 (2010) 14245; PCCP 13 (2011) 12008; PCCP 13 (2011) 17689] works well also in the case of sucrose. The solvent-excluded volume effect plays the fundamental role because sucrose addition to water causes a marked increase in volume packing density due to the large size of sucrose molecules, that act as crowding agents.