Seed mass equalises the strength of positive and negative plant-plant interactions in a semi-arid grassland

The interplay and balance between positive and negative interactions are important and recurrent topics in plant ecology. If facilitation occurs because benefactors ameliorate stress, such balance may be driven by seed mass because stress tolerance and competitive ability of plants, particularly seedlings, are positively correlated with seed mass. Thus, small-seeded, stress-intolerant species may require facilitation, but not large-seeded ones. This would equalise the magnitudes of opposite-signed interactions because in small-seeded species, positive effects of facilitators and negative effects of competitors should be strong, while both effects should be weak in large-seeded species. To test this idea, we assessed the effects of interactions with four associated species on different components of the performance of ten focal species. As expected, the largest facilitative and competitive effects were recorded in small-seeded species, and positive interactions had similar magnitudes to negative ones for any given seed mass, especially when performance was integrated into lifelong fitness. Furthermore, the fact that small-seeded species seem to be strongly facilitated may explain why they are not outcompeted by large-seeded species. This is an alternative to other hypotheses explaining the coexistence of plants with different-sized seeds. The close balance between opposite-signed interactions in the presence of stress may also explain why interactions have strong effects on individuals (that interact with only a few species), but seemingly weaker effects on populations, where interactions between many species would cancel out.

Global dynamics of parasitism-competition systems with one host and multiple parasites

This paper studies a new parasitism-competition model with one host and multiple parasites, where a plant is the host and nectar robbers are the parasites that compete for nectar of the plant but do not kill and eat the host itself. Based on the plant-nectar-robber interaction, a parasitism model is derived, which is different from previous parasitism models. Then the two-species model is extended to an n-dimensional system characterizing one plant and multiple robbers. Using dynamical system theory, qualitative behavior of the two-species model is exhibited by excluding existence of periodic solution, and global dynamics of the n-species system in the positive octant are completely shown. The dynamics demonstrate necessary and sufficient conditions for the principle of competitive exclusion to hold. It is shown that when the principle of competitive exclusion holds, at least one of the robbers is driven into extinction by other parasites while the others coexist with the plant at a steady state; When the principle of competitive exclusion does not hold, nectar robbers either coexist at a steady state or both go to extinction. The result also demonstrates a mechanism by which abiotic factors lead to persistence of nectar robbing.

ITC Measurement for High-Affinity Aptamers Binding to Their Target Proteins

Aptamers are nucleic acid molecules that bind to a target molecule with high affinity and specificity, which are generated by a process known as systematic evolution of ligands by exponential enrichment (SELEX). Because of their high affinity and specificity, aptamers were developed as therapeutic agents. Although aptamers are investigated as promising therapeutic agents, the mechanism of their high affinity and specificity is not clear. Therefore, structural and biophysical studies are important to know that. To date, ITC is increasingly being used to study the thermodynamic basis of aptamer-target protein interactions. Understanding the mechanism of aptamer binding would contribute to their development for therapeutic applications. In this chapter, we describe the protocol to study the thermodynamics of aptamer-protein interactions.

The flightin gene is necessary for the emission of vibrational signals in the rice brown planthopper (Nilaparvata lugens Stǻl)

In duet-based courtship, species- and sex-specific vibrational signals enable animals to identify the species and sex of the singer and also provide the necessary information with which to locate a partner. Substrate-borne communication has been described in a wide variety of insects. Here, we focus on the gene necessary for the emission of male vibrational signals and whether the male song fulfills such a functional role in the mating system of the brown planthopper (BPH, Nilaparvata lugens). We generated mute BPH adult males via RNA interference (RNAi) of the flightin gene, which encodes a myosin-binding protein expressed exclusively in the dorsal longitudinal muscle (DLM) in the basal two abdominal segments used for driving the vibration of the male-specific tymbal structure in short-winged (brachypterous) BPH adults. Transmission electron microscopy (TEM) observation showed that flightin knockdown disrupted the normal sarcomere structure of the abdominal DLM. No courtship song could be detected in the brachypterous males after RNAi treatment. Behavior and competition trials showed that the lack of male courtship songs prolonged copulation latency and even caused female rejection. Unexpectedly, the mute males exhibited greater competitiveness when competing against normal males.

Analysis of Proteus mirabilis Social Behaviors on Surfaces

The opportunistic pathogen Proteus mirabilis engages in visually dramatic and dynamic social behaviors. Populations of P. mirabilis can rapidly occupy surfaces, such as high-percentage agar and latex, through a collective surface-based motility termed swarming. When in these surface-occupying swarm colonies, P. mirabilis can distinguish between clonal siblings (self) and foreign P. mirabilis strains (nonself). This ability can be assessed by at least two standard methods: boundary formation, aka a Dienes line, and territorial exclusion. Here we describe methods for quantitative analysis of swarm colony expansion, of boundary formation, and of territorial exclusion. These assays can be employed to assess several aspects of P. mirabilis sociality including collective swarm motility, competition, and self versus nonself recognition.

Insights into the methanogenic degradation of N, N-dimethylformamide: The functional microorganisms and their ecological relationships

The methanogenic degradation of N, N-dimethylformamide (DMF) was investigated using anaerobic digested sludge (ADS), aerobic activated sludge (AAS) and co-cultured sludge (CCS), respectively. Both the metabolic pathway and the corresponding microorganisms which function in the methanogenic degradation of DMF were elucidated. DMF was unable to be degraded anaerobically by ADS due to the lack of DMF-hydrolyzing bacteria. DMF can be effectively degraded by AAS, however, no methane was recovered under the aerobic condition. The co-culture of DMF-hydrolyzing bacteria and methanogens in the CCS allowed for both hydrolysis of DMF and methane production to proceed successfully under the anaerobic condition, realizing the complete conversion from DMF to methane. However, a niche overlap due to the competition for the intermediates lowered the abundance of DMF-hydrolyzing bacteria. The introduction of nitrate, timely replenishment of AAS, micro-aeration and co-digestion were likely to maintain a high abundance of DMF-hydrolyzing bacteria to ensure an effective hydrolysis.

Kinetic Modelling of Competition and Depletion of Shared miRNAs by Competing Endogenous RNAs

Non-coding RNAs play a key role in the post-transcriptional regulation of mRNA translation and turnover in eukaryotes. miRNAs, in particular, interact with their target RNAs through protein-mediated, sequence-specific binding, giving rise to extended and highly heterogeneous miRNA-RNA interaction networks. Within such networks, competition to bind miRNAs can generate an effective positive coupling between their targets. Competing endogenous RNAs (ceRNAs) can in turn regulate each other through miRNA-mediated crosstalk. Albeit potentially weak, ceRNA interactions can occur both dynamically, affecting, e.g., the regulatory clock, and at stationarity, in which case ceRNA networks as a whole can be implicated in the composition of the cell's proteome. Many features of ceRNA interactions, including the conditions under which they become significant, can be unraveled by mathematical and in silico models. We review the understanding of the ceRNA effect obtained within such frameworks, focusing on the methods employed to quantify it, its role in the processing of gene expression noise, and how network topology can determine its reach.

Social coping styles of lizards are reactive and not proactive in urban areas

Animals engage in social interactions with changes in their behaviour and physiology. Environmental challenges, however, can influence social interactions by adding additional stressors. Here, we investigated the effects of urbanisation on the behaviour and hormonal responses of a tropical lizard species, Psammophilus dorsalis, during social interactions. We recorded behaviour of males from suburban and rural areas during controlled encounters with other males and females. We then measured corticosterone and testosterone levels of individuals at 10 min intervals, from immediately after the social encounter to 30 min later and then at 120 min after the interaction period. We found that differences in social behaviours and subsequent hormone levels were largely driven by habitat, and not social context. Overall, we found that fewer suburban males showed behavioural displays compared to rural males during social encounters. For those that displayed, intensity of aggression was similar across populations, but courtship intensity was lower for suburban males compared to rural males. Suburban males also had significantly elevated levels of corticosterone both under control conditions (no social encounter) and following intra- and intersexual interactions, while rural males retained low levels of corticosterone across contexts. Social interactions were associated with an increase in testosterone levels in all males, but only rural males maintained elevated levels for up to 120 min after interactions with females. Thus, lizards from these suburban and rural populations showed key differences in responsiveness to and recovery from social challenges, a pattern that suggests alternative coping styles ('proactive' vs. 'reactive'). These differences in social coping styles could influence consequences of sexual selection in an urbanised world.

Dynamics of two pathogens in a single tick population

A mathematical model for a two-pathogen, one-tick, one-host system is presented and explored. The model system is based on the dynamics of Amblyomma americanum, Rickettsia parkeri, and Rickettsia amblyommatis. The goal of this model is to determine how long an invading pathogen, R. parkeri, persists within a tick population, A. americanum, in which a resident pathogen, R. amblyommatis, is already established. The numerical simulations of the model demonstrate the parameter ranges that allow for coexistence of the two pathogens. Sensitivity analysis highlights the importance of vector-borne, tick-to-host, transmission rates on the invasion reproductive number and persistence of the pathogens over time. The model is then applied to a case study based on a reclaimed swampland field site in south-eastern Virginia using field and laboratory data. The results pinpoint the thresholds required for persistence of both pathogens in the local tick population. However, R. parkeri, is not predicted to persist beyond 3 years. Understanding the persistence and coexistence of tick-borne pathogens will allow public health officials increased insight into tick-borne disease dynamics.

Sexual Reproduction in the Fungal Foliar Pathogen Zymoseptoria tritici Is Driven by Antagonistic Density Dependence Mechanisms

This study provides empirical evidence for antagonistic density dependence mechanisms driving sexual reproduction in the wheat fungal pathogen Zymoseptoria tritici. Biparental crosses with 12 increasing inoculum concentrations, in controlled conditions, showed that sexual reproduction in Z. tritici was impacted by an Allee effect due to mate limitation and a competition with asexual multiplication for resource allocation. The highest number of ascospores discharged was reached at intermediate inoculum concentrations (from 5 × 10⁴ conidia mL^-1 to 10⁶ conidia mL^-1). Consistent with these results for controlled co-inoculation, we found that the intensity of sexual reproduction varied with both cropping period and the vertical position of the host tissues in the field, with a maximum between 25 and 35 cm above the ground. An optimal lesion density (disease severity of 30 to 45%) maximizing offspring (ascospores) number was established, and its eco-evolutionary consequences are considered here. Two ecological mechanisms may be involved: competition for resources between the two modes of reproduction (decrease in the host resources available for sexual reproduction due to their prior use in asexual multiplication), and competitive disequilibrium between the two parental isolates, due to differential interaction dynamics with the host, for example, leading to an imbalance between mating types. A conceptual model based on these results suggests that sexual reproduction plays a key role in the evolution of pathogenicity traits, including virulence and aggressiveness. Ecological knowledge about the determinants of sexual reproduction in Z. tritici may, therefore, open up new perspectives for the management of other fungal foliar pathogens with dual modes of reproduction.

Novel predators and anthropogenic disturbance influence spatio-temporal distribution of forest antelope species

Understanding the effects of anthropogenic disturbance on species' behaviour is crucial for conservation planning, considering the extent of habitat loss. We investigated the influence of anthropogenic disturbances including agriculture, urbanisation, protected areas, and the presence of novel predators, on the temporal and spatial behaviour of sympatric forest antelope (Tragelaphus scriptus, Philantomba monticola, Sylvicapra grimmia, and Cephalophus natalensis) in an anthropogenic matrix containing forest fragments in the Indian Ocean Coastal Belt of South Africa. We integrated land-use types with camera-trap data and compared activity patterns using circular statistics and occupancy modelling. Antelope species overlapped in temporal and spatial distribution and exhibited diurnal activity for 50% of the time. All species exhibited nocturnal activity for ∼25-33% of all observations, except for C. natalensis. Nocturnal activity varied between species and land-use types. The predators Canis familiaris, C. mesomelas and Caracal caracal negatively influenced occupancy of P. monticola, S. grimmia and C. natalensis. Humans negatively influenced temporal activity of P. monticola, and spatial distribution of T. scriptus and S. grimmia. C. familiaris had an overall negative influence on S. grimmia. We found spatial, and to a lesser extent temporal, segregation between species. However, plasticity in activity patterns existed, which varied in response to anthropogenic effects and novel predators.

Priority use of medium-chain fatty acids during high-intensity exercise in cross-country skiers

Background

One of the topics discussed in sports science is the use of medium-chain saturated fat as an energy-saving nutrient additive when approaching high-intensity exercise. The purpose of this study was to compare the blood concentrations of medium-chain and long-chain fatty acids (FAs) across different intensity loads.

Methods

Fifteen male highly trained athletes from the Russian cross-country skiing team participated in the study. Blood samples were drawn at rest, at the peak of veloergometric test with a growing exercise load till exhaustion (97–100% VO2max), and after competitions. The plasma FA profile was determined using gas-liquid chromatography.

Results

We observed a substantial increase in the concentrations of capric acid (С10:0) (+ 164.1%), lauric acid (С12:0) (+ 223.9%), and myristic acid (С14:0) (+ 130.2%) in skiers after a sprint distance (1.3 km). A less intense increase in the concentrations of these acids (p < 0.05) was observed after a middle length distance or cycle exercise «until exhaustion». No significant differences in long-chain saturated FA content relative to baselines during exercise tests or competitions were revealed.

Conclusions

In conclusion, the obtained results demonstrate activation of the lipolysis and the oxidation of medium-chain FA involved in the energy supply for highly trained athletes at maximum exercise loads.

Ecological divergence of burying beetles into the forest canopy

Closely related species with overlapping geographic ranges encounter a significant challenge: they share many ecological traits and preferences but must partition resources to coexist. In Ontario, potentially eleven species of carrion beetles (Coleoptera: Silphidae) live together and require vertebrate carrion for reproduction. Their reliance on an ephemeral and uncommon resource that is unpredictable in space and time is thought to create intense intra- and interspecific competition. Evidence suggests that burying beetle species reduce competition by partitioning carrion for breeding across different habitats, temperatures, and seasons. Here, we test predictions of an alternative axis for partitioning carrion: vertical partitioning between the ground and forest canopy. We conducted a survey of carrion beetles from May to July 2016 at the Queen's University Biological Station across 50 randomly generated points using baited lethal traps at zero and six metres. Ground traps yielded more species and individuals compared to those in the canopy, and the number of individuals and species caught increased through the season in both trap types. Ground and canopy traps were accurately distinguished by the presence or absence of three species: ground traps contained more Nicrophorus orbicollis and Necrophila americana, while canopy traps contained more Nicrophorus pustulatus. We trapped 253 N. pustulatus in the canopy, but only 60 on the ground. N. pustulatus is thought to be rare across its geographic range, but our results suggest it is uniquely common in canopy habitats, demonstrating a vertical partitioning of habitat and resources. Our results are consistent with N. pustulatus having diverged into canopy habitats as a strategy to coexist with closely related sympatric species when competing for similar resources. We still, however, do not know the traits that allow N. pustulatus to flourish in the canopy, exactly how N. pustulatus uses canopy resources for breeding, or the factors that restrict the expansion of other burying beetles into this habitat.

The success of the representation maintenance affects the memory-guided search processing: an ERP study

Previous evidence showed that working memory (WM) contents can bias visual selection. However, less is known about how the WM effects change when the WM representation is not held successfully. Here, we investigated this problem using event-related potentials. Subjects maintained a color in WM while performing a search task. The color cue contained the target (valid) or the distractor (invalid). Subjects could either remember the color accurately (correct WM) or not (incorrect WM). An N2-posterior contralateral component and a sustained posterior contralateral negativity (SPCN) were recorded in the valid and incorrect WM condition, while only an attenuated SPCN was elicited in the valid and correct WM condition. No reliable lateralized components were found for the invalid trials. These findings suggest that the WM effects on visual search are affected by the resource interchange between WM and search processes.

Haploid females in the isomorphic biphasic life-cycle of Gracilaria chilensis excel in survival

Background

Conditional differentiation is one of the most fundamental drivers of biodiversity. Competitive entities (usually species) differ in environmental or ecological niche enabling them to co-exist. Conditional differentiation of haploid and diploid generations is considered to be a requirement for the evolutionary stability of isomorphic biphasic life-cycles and the cause for the natural occurrence of both phases at uneven abundances. Theoretically, stage dependent survival rates are the most efficient way to explain conditional differentiation.

Results

We tested for conditional differentiation in survival rates among life stages (haploid males, haploid females, and diploids) of Gracilaria chilensis, an intertidal red alga occurring along the Chilean shores. Therefore, the fate of individuals was followed periodically for 3 years in five intertidal pools and, for the first time in isomorphic red algae, a composite model of the instantaneous survival rates was applied. The results showed the survival dependency on density (both competition and Allee effects), fertility, age, size, season and location, as well as the differentiation among stages for the survival dependencies of these factors. The young haploid females survived more than the young of the other stages under Allee effects during the environmentally stressful season at the more exposed locations, and under self-thinning during the active growth season. Furthermore, fertile haploid females had a higher survival than fertile haploid males or fertile diploids.

Conclusions

Here, we show a survival advantage of haploids over diploids. The haploid females probably optimize their resource management targeting structural and physiological adaptations that significantly enhance survival under harsher conditions. In a companion paper we demonstrate a fertility advantage of diploids over haploids. Together, the survival and fertility differentiation support the evolution and prevalence of biphasic life-cycles.

Electronic supplementary material

The online version of this article (10.1186/s12862-018-1285-z) contains supplementary material, which is available to authorized users.

Genomic overview of closely related fungi with different Protea host ranges

Genome comparisons of species with distinctive ecological traits can elucidate genetic divergence that influenced their differentiation. The interaction of a microorganism with its biotic environment is largely regulated by secreted compounds, and these can be predicted from genome sequences. In this study, we considered Knoxdaviesia capensis and Knoxdaviesia proteae, two closely related saprotrophic fungi found exclusively in Protea plants. We investigated their genome structure to compare their potential inter-specific interactions based on gene content. Their genomes displayed macrosynteny and were approximately 10 % repetitive. Both species had fewer secreted proteins than pathogens and other saprotrophs, reflecting their specialized habitat. The bulk of the predicted species-specific and secreted proteins coded for carbohydrate metabolism, with a slightly higher number of unique carbohydrate-degrading proteins in the broad host-range K. capensis. These fungi have few secondary metabolite gene clusters, suggesting minimal competition with other microbes and symbiosis with antibiotic-producing bacteria common in this niche. Secreted proteins associated with detoxification and iron sequestration likely enable these Knoxdaviesia species to tolerate antifungal compounds and compete for resources, facilitating their unusual dominance. This study confirms the genetic cohesion between Protea-associated Knoxdaviesia species and reveals aspects of their ecology that have likely evolved in response to their specialist niche.

Can intrinsic foraging efficiency explain dominance status? A test with functional response experiments

The functional response describes how food abundance affects the intake rate of foraging individuals, and as such, it can influence a wide range of ecological processes. In social species, dominance status can affect the functional response of competing individuals, but studies conducted in an interference-free context have provided contrasting results on the extent of between-individual variability in functional response. We tested the prediction that individuals intrinsically differ in their functional response, and that these differences could predict body weight and dominance status in social species. We used goats as a model species and performed foraging experiments to assess the functional response of these goats in an interference-free context. Our results show that some individuals are consistently better foragers than others, and these individuals were more likely to be heavier and dominant. Parameters of the functional response are, however, more strongly associated with dominance status than with body weight. We conclude that interference while foraging is not needed to explain body weight differences between dominant and subordinate individuals. We suggest that these differences can emerge from intrinsic differences in foraging efficiency between individuals, which could also allow better foragers to demonstrate greater tenacity during agonistic interactions.

Dominance hierarchy establishment in the invasive round goby, Neogobius melanostomus

Organisms living at high densities may be forced to engage in conflict for access to resources such as food or shelter. When these resources are limited, the outcome of interactions may have important fitness implications. We investigated the behavioural interactions of the invasive Round Goby (Neogobius melanostomus) in a shelter-limited environment. Round Goby are benthic fish that utilize rocky shelters for predator avoidance and as reproductive sites in which territorial males defend clutches of eggs. Previous work on this and other species has shown that larger individuals have greater resource holding potential in dyadic interactions. In order to understand the outcome of agonistic interactions in more complex social environments, we observed groups of three goby of the same sex which varied in relative size in an aquarium in which individuals had the opportunity to compete for access to shelters. We predicted that larger goby would behave aggressively towards smaller goby, and outcompete smaller goby for access to shelters. Because males defend shelters while breeding, we also predicted that male goby would compete more aggressively than females over dominance status. We found that larger goby in groups were socially dominant to smaller goby, regardless of sex. Additionally, we found that the largest goby in each group was involved in more aggressive interactions than the second or third largest goby in each group. We found no effect of relative size or sex on aggressive interaction or the emergent dominance relationships. Our findings highlight that aspects of the social environment may limit the opportunity for individuals to establish dominance or establish ownership of resources.

Can schools fairly select their students?

Selection within the educational domain breeds a special kind of suspicion. Whether it is the absence of transparency in the selection procedure, the observable outcomes of the selection, or the criteria of selection itself, there is much to corroborate the suspicion many have that selection in practice is unfair. And certainly as it concerns primary and secondary education, the principle of educational equity requires that children not have their educational experiences or opportunities determined by their postcode, their ethnic status, first language, or family wealth. Indeed educational opportunities determined by unearned advantage or disadvantage offend against basic notions of fairness. But are public schools even permitted to select their students, and if so, how can selection procedures used by schools be best structured to achieve equitable ends? In this article we delineate, describe, and defend what we believe are the essential features of selection and also why we need to pay equal attention to both the outcomes and the processes leading to those outcomes. Provided the selection is motivated and guided by the right reasons, as well as appropriately monitored, we argue that selection can be equity promoting.

Competition as a Means for Improving Academic Scores and Attendance at Education Conference

OBJECTIVE

To determine the effectiveness of competition on education conference attendance rate with a secondary goal of increased performance on in-service examination performance within a single academic general surgery residency.

DESIGN

By using a competition-based model of learning, we aimed to increase the overall resident attendance to weekly education conference as well as performance on in-service examination. Residents were given weekly reading assignments which were supplemented with lectures from faculty with expert knowledge of a given topic on a weekly basis. The ability of the surgical resident to apply this knowledge in a board-style exam was then tested on a weekly by administering a 10-question quiz.

SETTING

The program was implemented at Robert Wood Johnson Medical School, an academic surgical residency program.

RESULTS

The competition-based model of learning had improved conference attendance rates from 52% to 90% Overall quiz participation rates were 90.3% (SEM = 6.32%). Of the 5 distinct postgraduate levels performing on the weekly quizzes, the postgraduate year (PGY) 3 class performed best with the highest scores through 8 weeks. The next highest scoring class was the PGY 4 class. Overall average scores were 76% (standard deviation 10%). American Board of Surgery In-Training Examination scores did not significantly change between the observed years. Overall the average percentile for 2016 American Board of Surgery In-Training Examination was 55.3 compared to 2017's 47.4 (p = 0.0906).

CONCLUSIONS

After adding competition to our weekly education conference, we were able to improve our overall education conference attendance. Although this change did not have any objective changes measured on in-service examination results, we feel the increase in attendance and participation within education conference can only serve to benefit the surgical trainee. The establishment of this program has increased resident academic expectations, and a formalized guest-attending lecture schedule only drives conference participation higher. The establishment of weekly quizzes for and by residents allows the student to be more involved in their own education, and that of their peers.

Market structure and competition in the healthcare industry : Results from a transition economy

The present paper provides first empirical evidence on the relationship between market size and the number of firms in the healthcare industry for a transition economy. We estimate market-size thresholds required to support different numbers of suppliers (firms) for three occupations in the healthcare industry in a large number of distinct geographic markets in Slovakia, taking into account the spatial interaction between local markets. The empirical analysis is carried out for three time periods (1995, 2001 and 2010) which characterise different stages of the transition process. Our results suggest that the relationship between market size and the number of firms differs both across industries and across periods. In particular, we find that pharmacies, as the only completely liberalised market in our dataset, experience the largest change in competitive behaviour during the transition process. Furthermore, we find evidence for correlation in entry decisions across administrative borders, suggesting that future market analysis should aim to capture these regional effects.

[School-based tobacco prevention: the "Be Smart - Don't Start" program]

The competition for smoke-free classes, the "Be Smart - Don't Start" program has been implemented in Germany since 1997. Using contract management techniques, school classes participating in the competition commit themselves to abstain from smoking for six months. Classes report on a regular basis whether they have stayed smoke-free or not. After the end of the competition period, successful classes participate in a prize draw. The competition aimes to influence social norms.Over the past 20 years, the competition has become a major school-based intervention to prevent smoking in Germany. Several studies addressed process and outcome evaluation, cost-benefit efficacy and iatrogenic effects. Following the evidence so far, the intervention is feasible for implementation in school routines, evokes positive feedback in teachers and students, and reveals a positive cost-benefit ratio. Findings from controlled studies imply that negative side-effects are unlikely to occur and that participation in the competition affects the progression of smoking positively at least in the short term.

Effects of different dosages of caffeine administration on wrestling performance during a simulated tournament

The aim of the present study was to investigate the effects of different forms of caffeine administration on physical performance during a simulated wrestling tournament. In a double-blind and randomized experiment, twelve male freestyle wrestlers competed in a simulated wrestling tournament (5 wrestling matches consisting of 2 × 3-min wrestling rounds) following the ingestion of: a placebo, a high-dose of caffeine (10 mg/kg), a moderate-dose caffeine (4 mg/kg), a repeated-dose caffeine (2 mg/kg before each match to a total of 10 mg/kg) or a selective caffeine administration based on performance decrement previously measured (6.16 ± 1.58 mg/kg). The Pittsburgh Wrestling Performance Test (PWPT) was measured before each match to assess physical performance. In comparison to the placebo, the high dose of caffeine only reduced PWPT time before the first match (56.8 ± 2.0 vs. 52.9 ± 1.8 s; p < .05). The moderate dose of caffeine did not affect PWPT performance during the tournament. Both, the repeated dose and the selective administration of caffeine reduced PWPT time with respect to the placebo in the third (66.7 ± 1.8 vs. 63.1 ± 1.4 s; p < .05) and fourth matches (72.3 ± 2.4 vs. 65.9 ± 1.3 s; p < .05). However, only the selective dose of caffeine reduced PWPT time before the fifth match (62.7 ± 3.0 vs. 56.3 ± 2.0; p < .05). The dosage and administration of caffeine affect the ergogenic effects obtained following the ingestion of this substance. An individualized protocol to provide caffeine when physical performance is expected to be reduced might improve wrestling performance during the latter stages of a tournament.

Contrasting indirect effects of an ant host on prey-predator interactions of symbiotic arthropods

Indirect interactions occur when a species affects another species by altering the density (density-mediated interactions) or influencing traits (trait-mediated interactions) of a third species. We studied variation in these two types of indirect interactions in a network of red wood ants and symbiotic arthropods living in their nests. We tested whether the ant workers indirectly affected survival of a symbiotic prey species (Cyphoderus albinus) by changing the density and/or traits of three symbiotic predators, i.e., Mastigusa arietina, Thyreosthenius biovatus and Stenus aterrimus, provoking, respectively, low, medium and high ant aggression. An ant nest is highly heterogeneous in ant worker density and the number of aggressive interactions towards symbionts increases with worker density. We, therefore, hypothesized that varying ant density could indirectly impact prey-predator interactions of the associated symbiont community. Ants caused trait-mediated indirect effects in all three prey-predator interactions, by affecting the prey capture rate of the symbiotic predators at different worker densities. Prey capture rate of the highly and moderately aggressed spider predators M. arietina and T. biovatus decreased with ant density, whereas the prey capture rate of the weakly aggressed beetle predator S. aterrimus increased. Ants also induced density-mediated indirect interactions as high worker densities decreased the survival rate of the two predatory spider species. These results demonstrate for the first time that a host can indirectly mediate the trophic interactions between associated symbionts. In addition, we show that a single host can induce opposing indirect effects depending on its degree of aggression towards the symbionts.

Functional EEG connectivity during competition

Background

Social behavior and interactions pervasively shape and influence our lives and relationships. Competition, in particular, has become a core topic in social neuroscience since it stresses the relevance and salience of social comparison processes between the inter-agents that are involved in a common task. The majority of studies, however, investigated such kind of social interaction via one-person individual paradigms, thus not taking into account relevant information concerning interdependent participants’ behavioral and neural responses. In the present study, dyads of volunteers participated in a hyperscanning paradigm and competed in a computerized attention task while their electrophysiological (EEG) activity and performance were monitored and recorded. Behavioral data and inter-brain coupling measures based on EEG frequency data were then computed and compared across different experimental conditions: a control condition (individual task, t0), a first competitive condition (pre-feedback condition, t1), and a second competitive condition following a positive reinforcing feedback (post-feedback condition, t2).

Results

Results showed that during competitive tasks participants’ performance was improved with respect to control condition (reduced response times and error rates), with a further specific improvement after receiving a reinforcing feedback. Concurrently, we observed a reduction of inter-brain functional connectivity (primarily involving bilateral prefrontal areas) for slower EEG frequency bands (delta and theta). Finally, correlation analyses highlighted a significant association between cognitive performance and inter-brain connectivity measures.

Conclusions

The present results may help identifying specific patterns of behavioral and inter-brain coupling measures associated to competition and processing of social reinforcements.