Interspecific Cooperation Research Articles

Succession of bacterial community during electroactive methanogenic biofilm development under microplastic manipulation

Electrochemical methanogenesis is a promising and reliable process to convert waste streams into CH4, where the electroactive methanogenic biofilms play a key role. However, given that microplastics (MP) have now been spread ubiquitously in the environment, their regulation on the performance and succession of methanogenesis biofilm remains an enigma. Herein, we developed the single-chamber electrochemical methanogenic systems to investigate how poly (ethylene terephthalate) MP (PET-MP) regulates methanogenic biofilm formation and microbial metabolisms. The microbial volume of biofilm formed under MP exposure was similar to that without exposure. However, the live/dead cell ratio of the microbes in the biofilm under the PET-MP exposure decreased significantly (p < 0.05). Correspondingly, the richness and diversity of the microbial community in the presence of MP were also lower. Network analysis implied the interspecific cooperation among the microbial communities to cope with the MP stress. Meanwhile, the biofilm produced more extracellular polymer substrates during the biofilm thickening, possibly as a defense against MP invasion. At the gene level, the content of methanogenic gene mcrA was found to positively linearly correlate with the cultivation cycles, both in presence (r = 0.945, p < 0.05) or absence of PET-MP (r = 0.913, p < 0.05). The outcomes of this study could provide insights into the practical application of electrochemical methanogenesis technology to upcycle the MP-polluted biowastes and to implement the Power&Waste-to-X concept better.

Calcium alternative on microbial dust suppressant and the mechanism of action

Calcium alternative is an important factor affecting microbial-induced carbonate precipitation (MICP) process of microbial dust suppressants, however, previous research only focused on a single strain. To analyze the impact of calcium alternative on microbial community, calcium alternative was introduced in the MICP process of treating coal dust with microbial dust suppressants. Results showed that calcium alternative affected the MICP process of the enriched microorganisms. During the growth period of 48 h, calcium alternative improved the species richness of the genera. Urease activity of the microbial community after calcium nitrate treatment could reach 7.48 mM min−1, and the bioavailability during mineralization cycle was 94.57%. The biochemical processes of MICP were more diversified, such as urea hydrolysis, organic oxidation and nitrate dissimilation reduction. In addition, the mechanisms of calcium tolerance were also diverse, such as osmotic adjustment, metabolism, signal transduction, and interspecific cooperation. Quorum sensing strategy was the dominant of defense mechanism. Next, dust suppression experiments showed that calcium nitrate microbial dust suppressant had strong dust suppression ability, with a rain erosion mass loss of 29.25%, and a wind erosion rate 0.92 g m−2·min−1 under the wind speed of 10 m/s. Although further study was still needed, the findings provided a theoretical basis for calcium alternative and exploited great potentials of microorganisms in coal dust suppression.

SCUBA noise alters community structure and cooperation at Pederson’s cleaner shrimp cleaning stations

Recreational SCUBA diving is widespread and increasing on coral reefs worldwide. Standard open-circuit SCUBA equipment is inherently noisy and, by seeking out areas of high biodiversity, divers inadvertently expose reef communities to an intrusive source of anthropogenic noise. Currently, little is known about SCUBA noise as an acoustic stressor, and there is a general lack of empirical evidence on community-level impacts of anthropogenic noise on coral reefs. Here, we conducted a playback experiment on Caribbean reefs to investigate impacts of SCUBA noise on fish communities and interspecific cooperation at ecologically important cleaning stations of the Pederson’s cleaner shrimp Ancylomenes pedersoni. When exposed to SCUBA-noise playback, the total occurrence of fishes at the cleaning stations decreased by 7%, and the community and cleaning clientele compositions were significantly altered, with 27% and 25% of monitored species being affected, respectively. Compared with ambient-sound playback, SCUBA-noise playback resulted in clients having to wait 29% longer for cleaning initiation and receiving 43% less cleaning; however, cheating, signalling, posing and time spent cleaning were not affected by SCUBA-noise playback. Our study is the first to demonstrate experimentally that SCUBA noise can have at least some negative impacts on reef organisms, confirming it as an ecologically relevant pollutant. Moreover, by establishing acoustic disturbance as a likely mechanism for known impacts of diver presence on reef animals, we also identify a potential avenue for mitigation in these valuable ecosystems.

Increase in Cd Tolerance through Seed-Borne Endophytic Fungus Epichloë gansuensis Affected Root Exudates and Rhizosphere Bacterial Community of Achnatherum inebrians.

Soil cadmium (Cd) pollution is a serious environmental problem imperiling food safety and human health. The endophyte Epichloë gansuensis can improve the tolerance of Achnatherum inebrians to Cd stress. However, it is still unknown whether and how the endophyte helps host plants build up a specific bacterial community when challenged by CdCl2. In this study, the responses of the structure and function of bacterial community and root exudates of E+ (E. gansuensis infected) and E- (E. gansuensis uninfected) plants to Cd stress were investigated. Analysis of bacterial community structure indicated that the rhizosphere bacterial community predominated over the root endosphere bacterial community in enhancing the resistance of CdCl2 in a host mediated by E. gansuensis. E+ plant strengthened the interspecific cooperation of rhizosphere bacterial species. Moreover, the analysis of root exudates demonstrated E. gansuensis and increased the contents of organic acids and amino acids under Cd stress, and most root exudates were significantly correlated with rhizosphere bacteria. These results suggested that E. gansuensis employed a specific strategy to recruit distinct rhizosphere bacterial species and relevant functions by affecting root exudates to improve the tolerance of the host to Cd stress. This study provides a firm foundation for the potential application of symbionts in improving phytostabilization efficiency.

Periphytic biofilms-mediated microbial interactions and their impact on the nitrogen cycle in rice paddies

Rice paddies are unique waterlogged wetlands artificially constructed for agricultural production. Periphytic biofilms (PBs) at the soil-water interface play an important role in rice paddies characterized by high nutrient input but low utilization efficiency. PBs are composed of microbial aggregates, including a wide variety of microorganisms (algae, bacteria, fungi, protozoa, and metazoa), extracellular polymeric substances and minerals (iron, aluminum, and calcium), which form an integrated food web and energy flux within a relatively stable micro-ecosystem. PBs are crucial to regulate and streamline the nitrogen cycle by neutralizing nitrogen losses and improving rice production since PBs can serve as both a sink by capturing surplus nitrogen and a source by slowly re-releasing this nitrogen for reutilization. Here the ecological advantages of PBs in regulating the nitrogen cycle in rice paddies are illustrated. We summarize the key functional importance of PBs, including the intricate and delicate community structure, microbial interactions among individual phylotypes, a wide diversity of self-produced organics, the active adaptation of PBs to constantly changing environments, and the intricate mechanisms by which PBs regulate the nitrogen cycle. We also identify the future challenges of microbial interspecific cooperation in PBs and their quantitative contributions to agricultural sustainability, optimizing nitrogen utilization and crop yields in rice paddies. ● Periphytic biofilms (PBs) are active microbial aggregates ubiquitously distributed in wetlands. ● PBs form a stable and intricate food web catalyzing biogeochemical cycling of soil nitrogen. ● PBs in rice paddies can improve nitrogen utilization efficiency by plants. ● PBs-mediated microbial interactions facilitate the nitrogen cycle cooperation among microorganisms, while self-produced organics and genomic adaptation are beneficial for the nitrogen cycle regulation by PBs.

Cooperation and Lateral Forces: Moving Beyond Bottom-Up and Top-Down Drivers of Animal Population Dynamics.

Biologists have long known that animal population dynamics are regulated by a combination of bottom-up (resource availability) and top-down forces (predation). Yet, economists have argued that human population dynamics can also be influenced by intraspecific cooperation. Despite awareness of the role of interspecific cooperation (mutualism) in influencing resource availability and animal population dynamics, the role of intraspecific cooperation (sociality) under different environmental conditions has rarely been considered. Here we examine the role of what we call “lateral forces” that act within populations and interact with external top-down and bottom-up forces in influencing population dynamics using an individual-based model linking environmental quality, intraspecific cooperation, and population size. We find that the proportion of cooperators is higher when the environment is poor and population sizes are greatest under intermediate resources levels due to the contrasting effects of resource availability on behavior and population size. We also show that social populations are more resilient to environmental change than non-social ones because the benefits of intraspecific cooperation can outweigh the effects of constrained resource availability. Our study elucidates the complex relationship between environmental harshness, cooperation, and population dynamics, which is important for understanding the ecological consequences of cooperation.

Ecological Linkages between a Biofilm Ecosystem and Reactor Performance: The Specificity of Biofilm Development Phases.

In biofilm-based engineered ecosystems, the reactor performance was closely linked to interspecies interactions within a biofilm ecosystem, whereas the ecological processes underpinning such linkage were still unenlightened. Herein, the principles of community succession and assembly were integrated to capture the ecological laws of biofilm development by molecular ecological networks and assembly model analysis based on the 16S rRNA sequencing analysis and metagenomics in a well-controlled moving bed biofilm reactor. At the initial colonization phase (days 0-2, driven by initial colonizers), interspecific cooperation (74.18%) facilitated initial biofilm formation, whereas some pioneers, and keystone species disappeared at later phases. At the accumulation phase (days 3-30, rapid biofilm development), interspecific cooperation (81.41 ± 5.07%) contributed to rapid biofilm development and keystone species were mainly involved in quorum sensing or positively correlated with extracellular polymeric substance production. At the maturation phase (days 31-106, a well-adapted quasi-equilibrium state), increased interspecific competition (32.74 ± 4.77%) and higher small-world property facilitated the rapid information transportation and pollutant treatment, and keystone species were positively correlated with the removal of COD and NH4+-N. Homogenizing dispersal diminished the contemporary community dissimilarities, while turnover but rather nestedness governed the temporal variations in the biofilm succession period. This study highlighted the specificity of ecological processes at distinct biofilm development phases, which would advance our understanding on the development-to-function linkages in biofilm-based treatment processes.

Characteristics of anammox granular sludge using color differentiation, and nitrogen removal performance of its immobilized fillers based on microbial succession

The characteristics of anammox granular sludge (AnGS) based on color differentiation, and the regulation mechanism of immobilized fillers in the system were investigated. The results showed that biomass content, EPS and activity of red AnGS (R1) were higher than those of brown AnGS (R2). Moreover, R1 showed nitrification, while R2 showed denitrification. Filamentous bacteria constituted the granule skeleton of R1, while R2 mainly constituted inorganic nucleation and granulation. Additionally, immobilization improved the contribution rate of Anammox, and involved different regulatory mechanisms. High-throughput sequencing analysis showed that R1 encapsulation biomass eliminated miscellaneous bacteria and established specific flora, while mixed encapsulated biomass of R1 and R2 re-formed a functional bacterial network, which strengthened interspecies cooperation. The R2 encapsulated biomass and AnAOB copy numbers were inferior and the interspecific cooperation was weak, resulting in an unsatisfactory nitrogen removal performance. These results can strengthen the understanding and optimization of AnGS and its immobilization system.

Understanding the influence of substrate when growing tumorspheres

BackgroundCancer stem cells are important for the development of many solid tumors. These cells receive promoting and inhibitory signals that depend on the nature of their environment (their niche) and determine cell dynamics. Mechanical stresses are crucial to the initiation and interpretation of these signals.MethodsA two-population mathematical model of tumorsphere growth is used to interpret the results of a series of experiments recently carried out in Tianjin, China, and extract information about the intraspecific and interspecific interactions between cancer stem cell and differentiated cancer cell populations.ResultsThe model allows us to reconstruct the time evolution of the cancer stem cell fraction, which was not directly measured. We find that, in the presence of stem cell growth factors, the interspecific cooperation between cancer stem cells and differentiated cancer cells induces a positive feedback loop that determines growth, independently of substrate hardness. In a frustrated attempt to reconstitute the stem cell niche, the number of cancer stem cells increases continuously with a reproduction rate that is enhanced by a hard substrate. For growth on soft agar, intraspecific interactions are always inhibitory, but on hard agar the interactions between stem cells are collaborative while those between differentiated cells are strongly inhibitory. Evidence also suggests that a hard substrate brings about a large fraction of asymmetric stem cell divisions. In the absence of stem cell growth factors, the barrier to differentiation is broken and overall growth is faster, even if the stem cell number is conserved.ConclusionsOur interpretation of the experimental results validates the centrality of the concept of stem cell niche when tumor growth is fueled by cancer stem cells. Niche memory is found to be responsible for the characteristic population dynamics observed in tumorspheres. The model also shows why substratum stiffness has a deep influence on the behavior of cancer stem cells, stiffer substrates leading to a larger proportion of asymmetric doublings. A specific condition for the growth of the cancer stem cell number is also obtained

Response of ammonia‐oxidizing archaea and bacteria to streptomycin sulfate and penicillin in coastal wetlands along the Bohai Rim

Antibiotics are pollutants that are constantly discharged into ocean and coastal wetlands and affect the growth and activity of microorganisms. Ammonia-oxidizing archaea (AOA) and bacteria (AOB), which are very important in the global nitrogen cycle, are affected by antibiotics in the environment as well. Antibiotics have different influences on AOA and AOB microbial communities due to their different biochemical compositions and metabolic mechanisms, which change the ammonia-oxidizing process in different environments. In this study, 62 samples from four typical coastal wetland types along the Bohai Rim were collected and treated with streptomycin sulfate and penicillin in the laboratory. The total ammonia oxidation rate decreased by 61.2–84.0% with streptomycin sulfate and decreased by 50.0–74.5% with penicillin. The significant change in abundance and community structure indicated that AOB were more inhibited than AOA by streptomycin sulfate and penicillin. Nevertheless, ecological network analysis verified that the internal association in the AOA community was more fragile than that in the AOB community. Moreover, the relationship between AOA and other nitrogen-transforming functional archaea weakened in the presence of antibiotics, while AOB established relationships with more nitrogen-transforming functional bacteria in the presence of antibiotics. Streptomycin sulfate had a stronger effect than penicillin due to the different inhibiting mechanisms of these antibiotics and the promotion of interspecific cooperation induced by penicillin in AOA.

Research Advances of Leptotrombidium scutellare in China.

Leptotrombidium scutellare is one of the 6 main vectors of scrub typhus in China. It has been found in more than 15 provinces of China. Especially in Yunnan, it was found to be mainly distributed in some mountainous areas with high altitude, low temperature and low precipitation. Rodents and some other small mammals were the most common hosts of L. scutellare. To date, more than 40 host species of L. scutellare have been recorded with very low host specificity, and the main hosts varied in different geographical regions. L. scutellare had a strong resistance against the cold environment, and the temperature and humidity were 2 important factors affecting its growth and development. Among different individuals of their rodent hosts, L. scutellare mites often showed an aggregated distribution pattern, which reflected the interspecific cooperation of the mites. The chromosome karyotype of L. scutellare was 2n=16 and all the 8 pairs of chromosomes were short rod-shaped with metacentric or sub-metacentric types. The isozyme spectrum supported that L. scutellare, L. deliense and L. rubellum were in the same species group. Based on the natural infection, experimental transmission and epidemiological evidence, L. scutellare has been eventually confirmed as the second major vector of scrub typhus in China, which is second only to L. deliense.

Community lifespan, niche expansion and the evolution of interspecific cooperation.

Microbes live in dense and diverse communities where they deploy many traits that promote the growth and survival of neighbouring species, all the while also competing for shared resources. Because microbial communities are highly dynamic, the costs and benefits of species interactions change over the growth cycle of a community. How mutualistic interactions evolve under such demographic and ecological conditions is still poorly understood. Here, we develop an eco-evolutionary model to explore how different forms of helping with distinct fitness effects (rate-enhancing and yield-enhancing) affect the multiple phases of community growth, and its consequences for the evolution of mutualisms. We specifically focus on a form of yield-enhancing trait in which cooperation augments the common pool of resources, termed niche expansion. We show that although mutualisms in which cooperation increases partners growth rate are generally favoured at early stages of community growth, niche expansion can evolve at later stages where densities are high. Further, we find that niche expansion can promote the evolution of reproductive restraint, in which a focal species adaptively reduces its own growth rate to increase the density of partner species. Our findings suggest that yield-enhancing mutualisms are more prevalent in stable habitats with a constant supply of resources, and where populations typically live at high densities. In general, our findings highlight the need to integrate different components of population growth in the analysis of mutualisms to understand the composition and function of microbial communities.

Combining niche and game theories to address interspecific cooperation in ecological communities

Incorporating cooperative interspecific interactions into the classical Niche Theory has been identified as a big challenge of population and community ecology. Attempting to fill this gap I present the Lotka-Volterra Niche Game Model (LVNGM), resulting from the marriage between the classical Niche Theory and Game Theory. I use this new framework to analyze the effects of including cooperative interspecific interactions on two global properties of a community, its aggregate biomass or total yield and its biodiversity, measured by the Shannon equitability. I consider different dilemma games, games for which neither pure competition nor pure cooperation are dominant/optimal strategies, which are popular in biology: the Prisoner's Dilemma (PD), the Snowdrift (SD) and the Stag-Hunt (SH) games. The main result is that these games lead to a higher total yield—which is maximum for the SD, followed by the PD and the SH in third place—and, generally, to a higher biodiversity than pure competition. LVNGM allows gaining insights into niche construction/engineering. Examples in which LVNGM can be applied range from several single-trophic natural communities, in which positive interactions have been detected, to overyielding of artificial polycultures and plant-pollinator networks.

Back to the Future: A Glance Over Wolf Social Behavior to Understand Dog-Human Relationship.

Simple SummaryWolves, the ancestors of dogs, are one of the most cooperative canine species. This cooperative propensity derives from the fact that each subject needs other group members to obtain resources and increase survival. The pack functions as a unit in which each individual collaborates in territory defence, hunting, and rearing of offspring. For this reason, even though a clear hierarchy exists among wolves, subordinates can provide help to dominants to obtain social tolerance in a sort of commodity exchange. Wolves can make peace after aggression, console victims of a conflict, and calm down the aggressors. This set of behaviors, also called post-conflict strategies, requires a social attentiveness towards others’ emotional state and the ability to coordinate appropriate reactions. Adult wolves also play. They engage in play fighting, which strongly resembles real fighting, by finely modulating their motor actions and quickly interpreting playmates’ intentions, thus maintaining the non-serious playful mood. All these cognitive and social skills were a fertile ground for the artificial selection operated by humans to redirect the cooperative propensity of wolves towards dog–human affective relationship.This review focuses on wolf sociobiology to delineate the traits of cooperative baggage driven by natural selection (wolf-wolf cooperation) and better understand the changes obtained by artificial selection (dog-human cooperation). We selected some behaviors of the dog’s ancestors that provide the basis for the expression of a cooperative society, such as dominance relationships, leverage power, post-aggressive strategies, and playful dynamics between pack members. When possible, we tried to compare the data on wolves with those coming from the dog literature. Wolves can negotiate commodities when the interacting subjects occupy different ranking positions by bargaining social tolerance with helping and support. They are able to manage group disruption by engaging in sophisticated post-conflict maneuvers, thus restoring the relationship between the opponents and reducing the spreading of aggression in the group. Wolves engage in social play also as adults to manipulate social relationships. They are able to flexibly adjust their playful interactions to minimize the risk of escalation. Complex cognitive abilities and communicative skills are probably the main proximate causes for the evolution of inter-specific cooperation in wolves.

Synergistic degradation on aromatic cyclic organics of coal pyrolysis wastewater by lignite activated coke-active sludge process

In current study, the degradation of aromatic cyclic organics (ACOs) of coal pyrolysis wastewater (CPW) by lignite activated coke-active sludge (LAC-AS) process was investigated through the insight into synergistic effect of LAC and microbial community. As a contrast, the study on single AS process revealed that high phenols (>200 mg·L−1) exerted irreversible toxicity by eliminating biomass. Meanwhile, quinoline and naphthalene exhibited joint inhibition with phenols on bio-community. Absence of functional genus and insufficient interspecific cooperation caused interrupted biological reaction, leading to degenerated ecosystem and vicious circle. However, LAC-AS performed synergistic degradation of ACOs, leading to developed ecosystems and benign substance metabolisms. Specifically, LAC alleviated toxicity on suspended AS by ACOs adsorption, and the facultative bacteria enriched by LAC exerted synergistic degradation in biochemical processes. Firstly, the bacteria on biofilm facilitated direct interspecies electron transfer for ring-cleavage reaction, and electroactive bacteria (Cloacibacterium, Hydrogenophaga and Stenotrophomonas) were critical for the process. Secondly, suspended AS further degraded ring-cleavage products, achieving the interspecific cooperation with biofilm. The synergistic nitrogen metabolism by different paths also contributed to the benign metabolic circulation.

Microbial cross-feeding promotes multiple stable states and species coexistence, but also susceptibility to cheaters

Mutualism, interspecific cooperation that yields reciprocal benefits, can promote species coexistence, enhancing biodiversity. As a specific form of mutualism, cross-feeding, where each of two mutualists produces a resource the other one needs, has been broadly studied. However, few theoretical studies have examined competition between cross-feeding mutualists and cheaters, who do not synthesize resources themselves. In this paper we study a model with two mutualists, a cheater, two micronutrients that are synthesized and exchanged by the mutualists, and one macronutrient that is only from external supply. We investigate the coexistence of the species in the framework of resource competition theory. In particular, we examine the effect of the mutualists’ synthesis rates on their coexistence. In the absence of cheaters, multiple stable states occur if the synthesis rates are high, and higher synthesis rates increase the possibility that mutualists coexist. However, when the cheater is present, higher synthesis rates promote invasion by the cheater: If the cheater is superior on all three resources, it will either persist with at most one mutualist or even trigger extinction of all three species; if the cheater is only superior on the macronutrient, both mutualists may still coexist with the cheater. Our results provide a framework for further study on more complex mutualistic networks and real microbial communities.

Value of species and the evolution of conservation ethics.

The theory of evolution by natural selection can help explain why people care about other species. Building upon recent insights that morality evolves to secure fitness advantages of cooperation, we propose that conservation ethics (moral beliefs, attitudes, intuitions and norms regarding other species) could be adaptations that support cooperation between humans and non-humans. We present eco-evolutionary cost–benefit models of conservation behaviours as interspecific cooperation (altruism towards members of other species). We find that an evolutionary rule identical in structure to Hamilton's rule (which explains altruistic behaviour towards related conspecifics) can explain altruistic behaviour towards members of other species. Natural selection will favour traits for selectively altering the success of members of other species (e.g. conserving them) in ways that maximize inclusive fitness return benefits. Conservation behaviours and the ethics that evolve to reinforce them will be sensitive to local ecological and socio-cultural conditions, so will assume different contours in different places. Difficulties accurately assessing costs and benefits provided by other species, time required to adapt to ecological and socio-cultural change and barriers to collective action could explain the apparent contradiction between the widespread existence of conservation ethics and patterns of biodiversity decline globally.

Prokaryotic community successions and interactions in marine biofilms: the key role of Flavobacteriia.

Despite clear advances in characterizing marine biofilms, details on their formation and species succession remain scarce particularly during the early stage of development. We investigated the microbial community composition and succession in coastal marine biofilms on plastic. Samples were collected over 75 days of immersion with strengthened samplings during the early stages of biofilm establishment. Biofilm composition was estimated using Illumina Miseq and microbial community interactions were assessed through microbial association network analysis. In silico analyses showed that primers used in most of previous studies considerably underestimated marine biofilm diversity. Unintentionally ignored so far, we showed that Flavobacteriia might be key actors in the functioning of marine biofilms. Gamma-proteobacteria from the genus Oleibacter strongly dominated microbial communities during the first hours of biofilm formation. These pioneer communities were quickly replaced by alpha-proteobacteria and Flavobacteriia. Bacterial communities exhibited fast temporal structure dynamics with taxa displaying rapid increases and declines. A total of 90% of operational taxonomic units (OTUs) were intermittent or ephemeral reinforcing the conclusion that marine biofilms are highly dynamics. With 2/3 of positive significant connections between bacterial OTUs, microbial biofilm communities appear to be more inclined to develop inter-specific cooperation rather than competition and might thus form sets of functional guilds with mutual metabolic exchanges.

Empirical study of particle swarm optimization inspired by Lotka–Volterra model in Ecology

Particle swarm optimization (PSO) has been proved to be an effective technique in solving complex global optimization problems. Many modified versions of the original PSO algorithm emerged during the last 15 years. Many of those existing methods employ all particles in a single population which adopts the similar monotonic strategy. The loss of diversity resulted in the premature convergence problem. In this paper, we proposed a suite of multi-swarm Lotka–Volterra model inspired particle swarm optimization algorithms (MSLVPSO) to address the premature convergence problem. The intraspecific and interspecific cooperation and competition strategy of the proposed model dramatically increased diversity of particles. As a result, it makes the particles more likely to break away from the local optimum. In addition, we derived the method to set parameters and developed several cooperative–competitive schemes. We evaluated the proposed MSLVPSO algorithms using a variety of benchmark functions. We also compared our proposed method with typical single-swarm PSO algorithms. Our experimental results show that the proposed MSLVPSO optimizers outperform other state-of-the-art algorithms.

Spatial consequences for dolphins specialized in foraging with fishermen

According to theory, individuals forage in ways that maximize net energy intake. Distinct foraging strategies may emerge within a population in response to heterogeneous resources, competition and learning, among other drivers. We assessed individual variation in, and ecological consequences of, an unusual, specialized foraging tactic between animals and humans. In southern Brazil, bottlenose dolphins, Tursiops truncatus, herd fish schools towards artisanal fishermen, who cast nets in response to behavioural cues from the dolphins. This apparent cooperative tactic likely involves costs as well as benefits for both interacting parties, but such trade-offs remain poorly understood, especially for dolphins. We show that individual dolphins vary markedly in the frequency with which they interact with fishermen, and that this foraging variation is linked to ranging behaviour. Not all individual dolphins interact with fishermen; those that routinely do so concentrate around the limited interaction sites and have smaller home ranges than independent foragers. This suggests that foraging with fishermen increases foraging success and reduces search costs (i.e. foraging range). Competition for interaction sites may offset such benefits, since some individuals often forage at the high-quality sites while others forage at low-quality sites. Taken together, our findings suggest that two alternative tactics emerge in the population from trade-offs involving food access, foraging area, learning techniques and competition: dolphins either forage by themselves over larger areas on unpredictable resource patches (passing fish schools), or learn to interact with fishermen to access and compete for more predictable resource patches (interaction sites). By revealing some of the ecological drivers of this remarkable human–animal interaction, our study contributes two broader insights. First, specialized foraging can have ranging consequences for individuals and so structure the population spatially; second, interspecific cooperation may be founded upon intraspecific competition.