Hierarchically embedded scales of movement shape the social networks of vampire bats.

Social structure can emerge from hierarchically embedded scales of movement, where movement at one scale is constrained within a larger scale (e.g. among branches, trees, forests). In most studies of animal social networks, some scales of movement are not observed, and the relative importance of the observed scales of movement is unclear. Here, we asked: how does individual variation in movement, at multiple nested spatial scales, influence each individual's social connectedness? Using existing data from common vampire bats (Desmodus rotundus), we created an agent-based model of how three nested scales of movement-among roosts, clusters and grooming partners-each influence a bat's grooming network centrality. In each of 10 simulations, virtual bats lacking social and spatial preferences moved at each scale at empirically derived rates that were either fixed or individually variable and either independent or correlated across scales. We found that numbers of partners groomed per bat were driven more by within-roost movements than by roost switching, highlighting that co-roosting networks do not fully capture bat social structure. Simulations revealed how individual variation in movement at nested spatial scales can cause false discovery and misidentification of preferred social relationships. Our model provides several insights into how nonsocial factors shape social networks.

A scoping review of human health co-benefits of forest-based climate change mitigation in Europe.

Climate change is a pressing global challenge with profound implications for human health. Forest-based climate change mitigation strategies, such as afforestation, reforestation, and sustainable forest management, offer promising solutions to mitigate climate change and simultaneously yield substantial co-benefits for human health. The objective of this scoping review was to examine research trends related to the interdisciplinary nexus between forests as carbon sinks and human health co-benefits. We developed a conceptual framework model, supporting the inclusion of exposure pathways, such as recreational opportunities or aesthetic experiences, in the co-benefit context. We used a scoping review methodology to identify the proportion of European research on forest-based mitigation strategies that acknowledge the interconnection between mitigation strategies and human impacts. We also aimed to assess whether synergies and trade-offs between forest-based carbon sink capacity and human co-benefits has been analysed and quantified. From the initial 4,062 records retrieved, 349 reports analysed European forest management principles and factors related to climate change mitigation capacity. Of those, 97 studies acknowledged human co-benefits and 13 studies quantified the impacts on exposure pathways or health co-benefits and were included for full review. Our analysis demonstrates that there is potential for synergies related to optimising carbon sink capacity together with human co-benefits, but there is currently a lack of holistic research approaches assessing these interrelationships. We suggest enhanced interdisciplinary efforts, using for example multideterminant modelling approaches, to advance evidence and understanding of the forest and health nexus in the context of climate change mitigation.

Social regulation of arginine vasopressin and oxytocin systems in a wild group-living fish.

The neuropeptides arginine vasopressin (AVP) and oxytocin (OXT) are key regulators of social behaviour across vertebrates. However, much of our understanding of how these neuropeptide systems interact with social behaviour is centred around laboratory studies which fail to capture the social and physiological challenges of living in the wild. To evaluate relationships between these neuropeptide systems and social behaviour in the wild, we studied social groups of the cichlid fish Neolamprologus pulcher in Lake Tanganyika, Africa. We first used SCUBA to observe the behaviour of focal group members and then measured transcript abundance of key components of the AVP and OXT systems across different brain regions. While AVP is often associated with male-typical behaviours, we found that dominant females had higher expression of avp and its receptor (avpr1a2) in the preoptic area of the brain compared to either dominant males or subordinates of either sex. Dominant females also generally had the highest levels of leucyl-cystinyl aminopeptidase (lnpep)-which inactivates AVP and OXT-throughout the brain, potentially indicating greater overall activity (i.e., production, release, and turnover) of the AVP system in dominant females. Expression of OXT and its receptors did not differ across social ranks. However, dominant males that visited the brood chamber more often had lower preoptic expression of OXT receptor a (oxtra) suggesting a negative relationship between OXT signalling and parental care in males of this species. Overall, these results advance our understanding of the relationships between complex social behaviours and neuroendocrine systems under natural settings.

Colorful facial markings are associated with foraging rates and affiliative relationships in a wild group-living cichlid fish.

Many animals use color to signal their quality and/or behavioral motivations. Colorful signals have been well studied in the contexts of competition and mate choice; however, the role of these signals in nonsexual, affiliative relationships is not as well understood. Here, we used wild social groups of the cichlid fish Neolamprologus pulcher to investigate whether the size of a brightly colored facial patch was related to 1) individual quality, 2) social dominance, and/or 3) affiliative relationships. Individuals with larger patches spent more time foraging and tended to perform more aggressive acts against conspecific territory intruders. We did not find any evidence that the size of these yellow patches was related to social rank or body size, but dominant males tended to have larger patches than dominant females. Additionally, patch size had a rank-specific relationship with the number of affiliative interactions that individuals engaged in. Dominant males with large patches received fewer affiliative acts from their groupmates compared to dominant males with small patches. However, subordinates with large patches tended to receive more affiliative acts from their groupmates while performing fewer affiliative acts themselves. Taken together, our results suggest that patch size reflects interindividual variation in foraging effort in this cichlid fish and offer some of the first evidence that colorful signals may shape affiliative relationships within wild social groups.

Emergence of a Low-Energy Peak in the Smoothed Absolute Value Circular Dichroism Spectra of Small Helical Gold Nanorods.

We calculate, using time-dependent density functional theory, absorption and circular dichroism (CD) spectra for a series of small helical gold nanorod structures with a width of 0.6 nm and length increasing from 0.7 nm for Au24 to 1.9 nm for Au56. For a low-energy window, ranging from 1.7 to 4.1 eV, broadening the lines in the absorption spectra results in a low energy peak which previous studies have identified as the (localized) plasmon resonance. As expected, the absorption peak position of the plasmon resonance systematically redshifts as the length of the nanorod increases. However, trends in the CD and straightforwardly broadened CD spectra are more difficult to discern. We introduce the idea of an absolute value CD spectrum and show that broadening the lines results in a low energy peak that has not previously been reported. The peak position systematically redshifts as the length of the nanorod increases but over a significantly smaller range than that for the absorption spectrum.

Impact of Ion-Mixing Entropy on Orientational Preferences of DNA Helices: FRET Measurements and Computer Simulations.

Biological processes require DNA and RNA helices to pack together in specific interhelical orientations. While electrostatic repulsion between backbone charges is expected to be maximized when helices are in parallel alignment, such orientations are commonplace in nature. To better understand how the repulsion is overcome, we used experimental and computational approaches to investigate how the orientational preferences of DNA helices depend on the concentration and valence of mobile cations. We used Förster resonance energy transfer (FRET) to probe the relative orientations of two 24-bp helices held together via a freely rotating PEG linker. At low cation concentrations, the helices preferred more "cross"-like orientations over those closer to parallel, and this preference was reduced with increasing salt concentrations. The results were in good quantitative agreement with Poisson-Boltzmann (PB) calculations for monovalent salt (Na+). However, PB underestimated the ability of mixtures of monovalent and divalent ions (Mg2+) to reduce the conformational preference. As a complementary approach, we performed all-atom molecular dynamics (MD) simulations and found better agreement with the experimental results. While MD and PB predict similar electrostatic forces, MD predicts a greater accumulation of Mg2+ in the ion atmosphere surrounding the DNA. Mg2+ occupancy is predicted to be greater in conformations close to the parallel orientation than in conformations close to the crossed orientation, enabling a greater release of Na+ ions and providing an entropic gain (one bound ion for two released). MD predicts an entropy gain larger than that of PB because of the increased Mg2+ occupancy. The entropy changes have a negligible effect at low Mg2+ concentrations because the free energies are dominated by electrostatic repulsion. However, as the Mg2+ concentration increases, charge screening is more effective and the mixing entropy produces readily detectable changes in packing preferences. Our results underline the importance of mixing entropy of counterions in nucleic acid interactions and provide a new understanding on the impact of a mixed ion atmosphere on the packing of DNA helices.

Urban-rural disparity in global estimation of PM2·5 household air pollution and its attributable health burden.

BACKGROUND: Polluting fuels and inefficient stove technologies are still a leading cause of premature deaths worldwide, particularly in low-income and middle-income countries. Previous studies of global household air pollution (HAP) have neither considered the estimation of PM2·5 at national level nor the corresponding attributable mortality burden. Additionally, the effects of climate and ambient air pollution on the global estimation of HAP-PM2·5 exposure for different urban and rural settings remain largely unknown. In this study, we include climatic effects to estimate the HAP-PM2·5 exposure from different fuel types and stove technologies in rural and urban settings separately and the related attributable global mortality burden. METHODS: Bayesian hierarchical models were developed to estimate an annual average HAP-PM2·5 personal exposure and HAP-PM2·5 indoor concentration (including both outdoor and indoor sources). Model variables were selected from sample data in 282 peer-reviewed studies drawn and updated from the WHO Global HAP dataset. The PM2·5 exposure coefficients from the developed model were applied to the external datasets to predict the HAP-PM2·5 exposure globally (personal exposure in 62 countries and indoor concentration in 69 countries). Attributable mortality rate was estimated using a comparative risk assessment approach. Using weighted averages, the national level 24 h average HAP-PM2·5 exposure due to polluting and clean fuels and related death rate per 100 000 population were estimated. FINDINGS: In 2020, household use of polluting solid fuels for cooking and heating led to a national-level average personal exposure of 151 µg/m3 (95% CI 133-169), with rural households having an average of 171 µg/m3 (153-189) and urban households an average of 92 µg/m3 (77-106). Use of clean fuels gave rise to a national-level average personal exposure of 69 µg/m3 (62-76), with a rural average of 76 µg/m3 (69-83) and an urban average of 49 µg/m3 (46-53). Personal exposure-attributable premature mortality (per 100 000 population) from the use of polluting solid fuels at national level was on average 78 (95% CI 69-87), with a rural average of 82 (73-90) and an urban average of 66 (57-75). The average attributable premature mortality (per 100 000 population) from the use of clean fuels at the national level is 62 (54-70), with a rural average of 66 (58-74) and an urban average of 52 (47-57). The estimated HAP-PM2·5 indoor concentration shows that the use of polluting solid fuels resulted in a national-level average of 412 µg/m3 (95% CI 353-471), with a rural average of 514 µg/m3 (446-582) and an urban average of 149 µg/m3 (126-173). The use of clean fuels (gas and electricity) led to an average PM2·5 indoor concentration of 135 µg/m3 (117-153), with a rural average of 174 µg/m3 (154-195) and an urban average of 71 µg/m3 (63-80). Using time-weighted HAP-PM2·5 indoor concentrations, the attributable premature death rate (per 100 000 population) from the use of polluting solid fuels at the national level is on average 78 (95% CI 72-84), the rural average being 84 (78-91) and the urban average 60 (54-66). From the use of clean fuels, the average attributable premature death rate (per 100 000 population) at the national level is 59 (53-64), the rural average being 68 (62-74) and the urban average 45 (41-50). INTERPRETATION: A shift from polluting to clean fuels can reduce the average PM2·5 personal exposure by 53% and thereby lower the death rate. For all fuel types, the estimated average HAP-PM2·5 personal exposure and indoor concentrations exceed the WHO's Interim Target-1 average annual threshold. Policy interventions are urgently needed to greatly increase the use of clean fuels and stove technologies by 2030 to achieve the goal of affordable clean energy access, as set by the UN in 2015, and address health inequities in urban-rural settings. FUNDING: Wellcome Trust, The Lancet Countdown, the Engineering and Physical Sciences Research Council, and the Natural Environment Research Council.

Engineering magic number Au19 and Au20 cage structures using electron withdrawing atoms.

Gold cages are a subset of gold nanoparticles and these structures are of major interest due to their favourable physiochemical properties. In order for these structures to be useful in applications, they must be chemically stable. The objective of this research is to transform non-magic number cage structures into magic number cage structures by the addition of electron-withdrawing groups on the cages. The electronic properties for Au19X and Au20X2 (X = F, Cl, Br, I) are calculated and observed. It is expected that the electron-withdrawing groups will remove the electron density from the gold cages and leave them positively charged. We first optimize the geometries of the initial gold cages and verify the structures are a local minima. From there, we attach our halogens to the gold cages and optimize the structures to determine the NICS values and HOMO-LUMO gaps. NICS values were found to be more negative when a more electronegative halogen was used. Calculations have found that Au19F and Au20F2 have the most negative NICS values, indicating greater spherical aromaticity. Iodine, being the least electronegative atom, had the most positive NICS value and smallest HOMO-LUMO gap. All calculations are compared to the magic cluster Au18 which satisfies Hirsh's 2(N + 1)2 rule for n = 2.

Galanin expression varies with parental care and social status in a wild cooperatively breeding fish.

As many busy parents will attest, caring for young often comes at the expense of having time to feed and care for oneself. Galanin is a neuropeptide that regulates food intake and modulates parental care; however, the relative importance of galanin in the regulation of feeding versus caring by parents has never been evaluated before under naturalistic settings. Here, we assessed how expression of the galanin system varied in two brain regions, the hypothalamus (which regulates feeding) and the preoptic area (which modulates social behaviours including care) in a wild cichlid fish, Neolamprologus pulcher. Females with young had higher hypothalamic expression of galanin receptor 1a, and the highest expression of galanin and galanin receptor 1a was observed in females that foraged the least. However, expression of five other feeding-related neuropeptides did not change while females were caring for young suggesting that changes in the hypothalamic galanin system may not have been directly related to changes in food intake. The preoptic galanin system was unaffected by the presence of young, but preoptic galanin expression was higher in dominant females (which are aggressive, regularly reproduce and care for young) compared to subordinate females (which are submissive, rarely reproduce but often help care for young). Additionally, preoptic galanin expression was higher in fish that performed more territory defense. Overall, our results indicate that galanin has brain-region-specific roles in modulating both parental care and social status in wild animals.

An adaptive dynamic model of a vigilance game among group foragers.

In group foraging animals, vigilance tends to decrease as group size increases. A forager in a group receives a vigilance benefit not only when it is being vigilant itself but also when a group mate is being vigilant. The many eyes hypothesis supposes that individuals exhibit lower vigilance in larger groups because of this. However, changes in safety resulting from the vigilance benefit conferred by group mates can change the decision to join or leave a group so as vigilance changes because of changes in group size, group size may also change in response to changes in vigilance. Additionally, individuals may have poor information about the vigilance strategies of their neighbors. We present a game theoretical model of vigilance that incorporates dynamic group sizes and does not require behavioral monitoring of the vigilance strategies of others. For systems at equilibrium, maximum vigilance decreases with increased group size. Furthermore, by varying intraspecific competition we show an inverse relationship between group size and vigilance. Thus, we provide a mechanism in support of the many eyes hypothesis from an evolutionary game theory perspective and conclude that variation in intraspecific competition and its effect on group size may be responsible for the relationship.

Emergence of size-structured dominance hierarchies through size-dependent feedback.

Size-based dominance hierarchies influence fitness, group size and population dynamics and link dominance structure to evolutionary and ecological outcomes. While larger individuals often gain dominance, social status may influence growth and size in return, resulting in feedbacks among status, growth and size. Here, we present two models evaluating how these feedbacks influence the emergence of size structure in a dominance hierarchy. In the first, size influences competition for food and investment in suppressing growth of groupmates. Stable size differences emerged when suppression was greatest for similarly sized individuals and size had little effect on competition for food. The model predicted size divergence when size strongly affected competition for food. In the second model, we used a dynamic game to solve for optimal investment in growth suppression as a function of size structure. Investment in growth suppression was favoured only when dominants and subordinates were similar in size, generating size ratios different than those expected by chance. Variation in the feedbacks among growth, size and status can explain variation in emergent size structure of dominance hierarchies and its consequences for conflict within groups. This article is part of the theme issue 'The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies'.

Direct Measurement of Interhelical DNA Repulsion and Attraction by Quantitative Cross-Linking.

To better understand the forces that mediate nucleic acid compaction in biology, we developed the disulfide cross-linking approach xHEED (X-linking of Helices to measure Electrostatic Effects at Distance) to measure the distance-dependent encounter frequency of two DNA helices in solution. Using xHEED, we determined the distance that the electrostatic potential extends from DNA helices, the dependence of this distance on ionic conditions, and the magnitude of repulsion when two helices approach one another. Across all conditions tested, the potential falls to that of the bulk solution within 15 Å of the major groove surface. For separations of ∼30 Å, we measured a repulsion of 1.8 kcal/mol in low monovalent ion concentration (30 mM Na+), with higher Na+ concentrations ameliorating this repulsion, and 2 M Na+ or 100 mM Mg2+ eliminating it. Strikingly, we found full screening at very low Co3+ concentrations and net attraction at higher concentrations, without the higher-order DNA condensation that typically complicates studies of helical attraction. Our measurements define the relevant distances for electrostatic interactions of nucleic-acid helices in biology and introduce a new method to propel further understanding of how these forces impact biological processes.

Causes and consequences of variation in development time in a field cricket.

Variation in development time can affect life-history traits that contribute to fitness. In Gryllus vocalis, a non-diapausing cricket with variable development time, we used a path analysis approach to determine the causative relationships between parental age, offspring development time and offspring life-history traits. Our best-supported path model included both the effects of parental age and offspring development time on offspring morphological traits. This result suggests that offspring traits are influenced by both variation in acquisition of resources and trade-offs between traits. We found that crickets with longer development times became larger adults with better phenoloxidase-based immunity. This is consistent with the hypothesis that crickets must make a trade-off between developing quickly to avoid predation before reproduction and attaining better immunity and a larger adult body size that provides advantages in male-male competition, mate choice and female fecundity. Slower-developing crickets were also more likely to be short-winged (unable to disperse by flight). Parental age has opposing direct and indirect effects on the body size of daughters, but when both the direct and indirect effects of parental age are taken into account, younger parents had smaller sons and daughters. This pattern may be attributable to a parental trade-off between the number and size of eggs produced with younger parents producing more eggs with fewer resources per egg. The relationships between variables in the life-history traits of sons and daughters were similar, suggesting that parental age and development time had similar causative effects on male and female life-history traits.