Should I Stay or Should I Go? A Habitat-Dependent Dispersal Kernel Improves Prediction of Movement

The analysis of animal movement within different landscapes may increase our understanding of how landscape features affect the perceptual range of animals. Perceptual range is linked to movement probability of an animal via a dispersal kernel, the latter being generally considered as spatially invariant but could be spatially affected. We hypothesize that spatial plasticity of an animal''s dispersal kernel could greatly modify its distribution in time and space. After radio tracking the movements of walking insects (Cosmopolites sordidus) in banana plantations, we considered the movements of individuals as states of a Markov chain whose transition probabilities depended on the habitat characteristics of current and target locations. Combining a likelihood procedure and pattern-oriented modelling, we tested the hypothesis that dispersal kernel depended on habitat features. Our results were consistent with the concept that animal dispersal kernel depends on habitat features. Recognizing the plasticity of animal movement probabilities will provide insight into landscape-level ecological processes.     

Mate Recognition: Should Fly Stay or Should Fly Go?

Recent studies have shown that male fruit flies use close-range olfactory cues to assess the status of potential mating partners. The presence of a volatile, male-derived pheromone can suppress the default male behavioral state of courting females.     

Should I Stay or Should I Go? Presynaptic Boutons in the Adult Cortex Still Haven't Made Up Their Minds

Previous studies demonstrating turnover of the dendritic spines of cortical neurons have suggested a modest rate of turnover of synaptic connections. Now, two papers in this issue of Neuron address this question from the other side of the synapse, the presynaptic boutons. Both studies use in vivo multiphoton imaging of cortical axons to show that synaptic boutons come and go, just like spines. One of the studies shows remarkable diversity in the lability of boutons depending on the cell type from which they originate, with some boutons displaying nearly complete turnover in just a few months. The other study shows that bouton turnover occurs in primates as well as rodents.     

Should I Stay or Should I Go? Dispersal and Population Structure in Small,Isolated Desert Populations of West African Crocodiles

The maintenance of both spatial and genetic connectivity is paramount to the long-term persistence of small, isolated populations living in environments with extreme climates. We aim to identify the distribution of genetic diversity and assess population sub-structuring and dispersal across dwarfed desert populations of Crocodylus suchus, which occur in isolated groups, usually less than five individuals, along the mountains of Mauritania (West Africa). We used both invasive and non-invasive sampling methods and a combination of mitochondrial DNA (12 S and ND4) and microsatellite markers (32 loci and a subset of 12 loci). Our results showed high genetic differentiation and geographic structure in Mauritanian populations of C. suchus. We identified a metapopulation system acting within four river sub-basins (high gene flow and absence of genetic structure) and considerable genetic differentiation between sub-basins (F _ST range: 0.12–0.24) with rare dispersal events. Effective population sizes tend to be low within sub-basins while genetic diversity is maintained. Our study suggests that hydrographic networks (temporal connections along seasonal rivers during rainy periods) allow C. suchus to disperse and maintain metapopulation dynamics within sub-basins, which attenuate the loss of genetic diversity and the risk of extinction. We highlight the need of hydrographic conservation to protect vulnerable crocodiles isolated in small water bodies. We propose C. suchus as an umbrella species in Mauritania based on ecological affinities shared with other water-dependent species in desert environments.     

Should I Stay or Should I Go? Eukaryotic Translation Initiation Factors 1 and 1A Control Start Codon Recognition

Start codon selection is a key step in translation initiation as it sets the reading frame for decoding. Two eukaryotic initiation factors, eIF1 and eIF1A, are key actors in this process. Recent work has elucidated many details of the mechanisms these factors use to control start site selection. eIF1 prevents the irreversible GTP hydrolysis that commits the ribosome to initiation at a particular codon. eIF1A both promotes and inhibits commitment through the competing influences of its two unstructured termini. Both factors perform their tasks through a variety of interactions with other components of the initiation machinery, in many cases mediated by the unstructured regions of the two proteins.     

Plant Development: Should I Stop or Should I Grow?

Plant growth is tightly controlled through the integration of environmental cues with the physiological status of the seedling. A recent study now proposes a model explaining how the plant hormone ethylene triggers opposite growth responses depending on the light environment.     

Should I Stay or Should I go? The Influence of Handling by Researchers on Den use in an Arboreal Nocturnal Rodent

Understanding how animals respond to disturbance by investigators is essential for a fair assessment of the presence of bias in routinely used research protocols. It is also an essential prerequisite for anyone interested in animal welfare and ethically sound research. Here, we utilize an automatic logging system to monitor nest box use by PIT‐tagged edible dormice, Glis glis, after standard handling procedures applied during a regular nest‐box monitoring programme. The edible dormouse is an arboreal nocturnal rodent that relies on tree hollows as daytime den sites. We assessed the effect of disturbance on dormice in two ways: whether it affected the decision of an individual to stay in the same den site for a subsequent day and whether it affected the timing of the individual's nocturnal emergence from the den site. We found handling had a strong negative effect on short‐term den use. In addition, females and sexually active individuals were more likely to spend the following day in the nest box. Individuals that had left the den site after our handling returned to them after an average of 4 d. Handling did not have a significant effect on the period of absence, but reproductively active animals returned on average after 3 d, while reproductively quiescent animals returned after more than 5 d. Manipulation did not have a significant effect on the initiation of nocturnal activity. Our study suggests that disturbance by investigators may modify certain aspects of animal behaviour, but this effect is likely to be short term and does not appear to impair the efficacy of routinely practiced capture‐mark‐recapture field protocols.     

Why Can’t Vertebrates Synthesize Trehalose?

The non-reducing disaccharide trehalose is a singular molecule, which has been strictly conserved throughout evolution in prokaryotes (bacteria and archaea), lower eukaryotes, plants, and invertebrates, but is absent in vertebrates and—more specifically—in mammals. There are notable differences regarding the pivotal roles played by trehalose among distantly related organisms as well as in the specific metabolic pathways of trehalose biosynthesis and/or hydrolysis, and the regulatory mechanisms that control trehalose expression genes and enzymatic activities. The success of trehalose compared with that of other structurally related molecules is attributed to its exclusive set of physical properties, which account for its physiological roles and have also promoted important biotechnological applications. However, an intriguing question still remains: why are vertebrates in general, and mammals in particular, unable (or have lost the capacity) to synthesize trehalose? The search for annotated genomes of vertebrates reveals the absence of any functional trehalose synthase gene. Indeed, this is also true for the human genome, which contains, however, two genes encoding for isoforms of the hydrolytic activity (trehalase). Although we still lack a convincing answer, this striking difference might reflect the divergent evolutionary lineages followed by invertebrates and vertebrates. Alternatively, some clinical data point to trehalose as a toxic molecule when stored inside the human body.     

Will They Stay or Will They Go? International Graduate Students and Their Decisions to Stay or Leave the U.S. upon Graduation

The U.S. currently enjoys a position among the world’s foremost innovative and scientifically advanced economies but the emergence of new economic powerhouses like China and India threatens to disrupt the global distribution of innovation and economic competitiveness. Among U.S. policy makers, the promotion of advanced education, particularly in the STEM (Science, Technology, Engineering and Mathematics) fields, has become a key strategy for ensuring the U.S.’s position as an innovative economic leader. Since approximately one third of science and engineering post-graduate students in the U.S. are foreign born, the future of the U.S. STEM educational system is intimately tied to issues of global competitiveness and American immigration policy. This study utilizes a combination of national education data, a survey of foreign-born STEM graduate students, and in-depth interviews of a sub-set of those students to explain how a combination of scientists’ and engineers’ educational decisions, as well as their experience in school, can predict a students’ career path and geographical location, which can affect the long-term innovation environment in their home and destination country. This study highlights the fact that the increasing global competitiveness in STEM education and the complex, restrictive nature of U.S. immigration policies are contributing to an environment where the American STEM system may no longer be able to comfortably remain the premier destination for the world’s top international students.     

‘Should I stay or should I go?’ Bacterial attachment vs biofilm formation on surface-modified membranes

A number of techniques are used for testing the anti-biofouling activity of surfaces, yet the correlation between different results is often questionable. In this report, the correlation between initial bacterial deposition (fast tests, reported previously) and biofilm growth (much slower tests) was analyzed on a pristine and a surface-modified reverse osmosis membrane ESPA-1. The membrane was modified with grafted hydrophilic polymers bearing negatively charged, positively charged and zwitter-ionic moieties. Using three different bacterial strains it was found that there was no general correlation between the initial bacterial deposition rates and biofilm growth on surfaces, the reasons being different for each modified surface. For the negatively charged surface the slowest deposition due to the charge repulsion was eventually succeeded by the largest biofilm growth, probably due to secretion of extracellular polymeric substances (EPS) that mediated a strong attachment. For the positively charged surface, short-term charge attraction by quaternary amine groups led to the fastest deposition, but could be eventually overridden by their antimicrobial activity, resulting in non-consistent results where in some cases a lower biofilm formation rate was observed. The results indicate that initial deposition rates have to be used and interpreted with great care, when used for assessing the anti-biofouling activity of surfaces. However, for a weakly interacting ‘low-fouling’ zwitter-ionic surface, the positive correlation between initial cell deposition and biofilm growth, especially under flow, suggests that for this type of coating initial deposition tests may be fairly indicative of anti-biofouling potential.     

Should I stay or should I go? Why Roma migrants leave or remain in nomad camps

Drawing on fieldwork conducted among Roma living in Turin (Northern Italy), this paper analyses the processes surrounding the exit routes taken by Roma out of nomad camps. Starting with the overview of national policy to face the disadvantaged housing situation, it explores the agency and the active strategy of Roma in the improvement of their disadvantaged living condition. Housing careers are the centre of the analysis in a comparative perspective: those of Roma leaving informal slums are compared with those of Roma leaving municipality camps. The article focuses on different factors and social mechanisms that explain different pathways, in the frame of constraints and opportunities. Individual preferences and resources, as well as institutional and structural constrains are part of the explanation. The results show the complexity of the universe of preferences and opportunities, stressing advantages and weaknesses of governmental policy and other external constraints in the decision-making processes.     

Organ Donation: Who Should Decide?—A Canadian Perspective

This paper examines an under-explored issue in organ donation: whose decision making authority should be privileged posthumously in the context of known, explicit consent for donation? Current practices in Canada support the family as the ultimate decision maker, despite the existence of legislative support in many Canadian provinces for the potential donor as legitimate decision maker. Arguments for and against privileging the family and the potential donor are identified. Informing the question of “who should decide” are considerations of individual and relational autonomy, distributive and social justice, personhood, and arguments “from distress”. Tensions and competing obligations emerge from an exploration of these considerations that call for further, inclusive dialogue and deliberation on this important organ donation issue.     

Should I stay or should I go? Nucleocytoplasmic trafficking in plant innate immunity

Communication between the cytoplasm and the nucleus is a fundamental feature of eukaryotic cells. Bidirectional transport of macromolecules across the nuclear envelope is typically mediated by receptors and occurs exclusively through nuclear pore complexes (NPCs). The components and molecular mechanisms regulating nucleocytoplasmic trafficking and signalling processes are well studied in animals and yeast but are poorly understood in plants. Current work shows that components of the NPC and the nuclear import and export machinery play essential roles in plant innate immunity. Translocation of defence regulators and Resistance (R) proteins between the cytoplasm and the nucleus are recently uncovered aspects of plant defence responses against pathogens. Future studies will reveal more details on the spatial and temporal dynamics and regulation of this process.