Strong Competitive Interactions Research Articles

Effects of material type and surface roughness of settlement tiles on macroalgal colonisation and early coral recruitment success

Sexual propagation of corals is a promising strategy for coral restoration, but one of the main challenges is the high mortality of coral spat due to competitive interactions with macroalgae during the early life history stages. Optimising the properties of settlement substrates such as material types and surface roughness has the potential to improve the survival of spat by limiting the recruitment and growth of macroalgae. In this study, we assessed the effects of modifying surface roughness across three different tile materials (alumina-based ceramic, calcium carbonate (CaCO3), and concrete) on the settlement success and post-settlement survivorship of Acropora kenti coral larvae in six mesocosm tanks, each with different established macroalgal communities. The macroalgal community compositions on the tiles were significantly different among material types, but not surface roughness, although the type and abundance of macroalgal species were heavily influenced by the established tank communities. Increasing surface roughness did not affect larval settlement success or spat survivorship. Substantially higher larval settlement density was found on concrete tiles (1.92 ± 0.10 larvae cm−2), but spat survival was the highest on CaCO3 tiles (73.4 ± 4.2% survived). Very strong competitive interactions were observed between spat and macroalgae, with overgrowth by the crustose coralline alga Crustaphytum sp. and the brown alga Lobophora sp. being the primary cause of spat mortality. Overall, when taking into account both settlement and survival rates, concrete was the best performing among the tile types tested here.

Metal sequestration by Microcystis extracellular polymers: a promising path to greener water treatment.

The problem of heavy metal pollution in water bodies poses a significant threat to both the environment and human health, as these toxic substances can persist in aquatic ecosystems and accumulate in the food chain. This study investigates the promising potential of using Microcystis aeruginosa extracellular polymeric substances (EPS) as an environmentally friendly, highly efficient solution for capturing copper (Cu2+) and nickel (Ni2+) ions in water treatment, emphasizing their exceptional ability to promote green technology in heavy metal sequestration. We quantified saccharides, proteins, and amino acids in M. aeruginosa biomass and isolated EPS, highlighting their metal-chelating capabilities. Saccharide content was 36.5mgg-1 in biomass and 21.4mgg-1 in EPS, emphasizing their metal-binding ability. Proteins and amino acids were also prevalent, particularly in EPS. Scanning electron microscopy (SEM) revealed intricate 3D EPS structures, with pronounced porosity and branching configurations enhancing metal sorption. Elemental composition via energy dispersive X-ray analysis (EDAX) identified essential elements in both biomass and EPS. Fourier transform infrared (FTIR) spectroscopy unveiled molecular changes after metal treatment, indicating various binding mechanisms, including oxygen atom coordination, π-electron interactions, and electrostatic forces. Kinetic studies showed EPS expedited and enhanced Cu2+ and Ni2+ sorption compared to biomass. Thermodynamic analysis confirmed exothermic, spontaneous sorption. Equilibrium biosorption studies displayed strong binding and competitive interactions in binary metal systems. Importantly, EPS exhibited impressive maximum sorption capacities of 44.81mgg-1 for Ni2+ and 37.06mgg-1 for Cu2+. These findings underscore the potential of Microcystis EPS as a highly efficient sorbent for heavy metal removal in water treatment, with significant implications for environmental remediation and sustainable water purification.

Linking the impact of bacteria on phytoplankton growth with microbial community composition and co-occurrence patterns

The interactions between microalgae and bacteria have recently emerged as key control factors which might contribute to a better understanding on how phytoplankton communities assemble and respond to environmental disturbances. We analyzed partial 16S rRNA and 18S rRNA genes from a total of 42 antibiotic bioassays, where phytoplankton growth was assessed in the presence or absence of an active bacterial community. A significant negative impact of bacteria was observed in 18 bioassays, a significant positive impact was detected in 5 of the cases, and a non-detectable effect occurred in 19 bioassays. Thalasiossira spp., Chlorophytes, Vibrionaceae and Alteromonadales were relatively more abundant in the samples where a positive effect of bacteria was observed compared to those where a negative impact was observed. Phytoplankton diversity was lower when bacteria negatively affect their growth than when the effect was beneficial. The phytoplankton-bacteria co-occurrence subnetwork included many significant Chlorophyta-Alteromonadales and Bacillariophyceae-Alteromonadales positive associations. Phytoplankton-bacteria co-exclusions were not detected in the network, which contrasts with the negative effect of bacteria on phytoplankton growth frequently detected in the bioassays, suggesting strong competitive interactions. Overall, this study adds strong evidence supporting the key role of phytoplankton-bacteria interactions in the microbial communities.

Bacterial community structure and assembly dynamics hinge on plant litter quality.

Litter decomposition is a fundamental ecosystem process controlling the biogeochemical cycling of energy and nutrients. Using a 360-day lab incubation experiment to control for environmental factors, we tested how litter quality (low C/N deciduous vs. high C/N coniferous litter) governed the assembly and taxonomic composition of bacterial communities and rates of litter decomposition. Overall, litter mass loss was significantly faster in soils amended with deciduous (DL) rather than coniferous (CL) litter. Communities degrading DL were also more taxonomically diverse and exhibited stochastic assembly throughout the experiment. By contrast, alpha-diversity rapidly declined in communities exposed to CL. Strong environmental selection and competitive biological interactions induced by molecularly complex, nutrient poor CL were reflected in a transition from stochastic to deterministic assembly after 180 days. Constraining how the diversity and assembly of microbial populations modulates core ecosystem processes, such as litter decomposition, will become increasingly important under novel climate conditions, and as policymakers and land managers emphasize soil carbon sequestration as a key natural climate solution.

Seasonal variation in dietary patterns and trophic niche overlap among three sympatric medium-sized carnivores in a cool-temperate zone

To understand and sustain carnivore communities and ecosystems, it is important to determine the mechanisms of coexistence and potential competitive interactions among carnivores. This study examined how carnivores coexist and how climatic environmental shifts affect the potential competitive interactions among medium-sized carnivores. The seasonal trophic niche overlap of red foxes, Japanese martens, and raccoon dogs in the cool-temperate zone in Japan was evaluated, where there are distinct seasonal changes, especially from heavy snowfall. Faecal analysis of red foxes (n = 107), Japanese martens (n = 125), and raccoon dogs (n = 100) from 2019 to 2021 showed that carnivores share the main food items and their annual dietary overlap is relatively high despite the co-occurrence of carnivores. These results have indicated that the carnivores have potentially strong competitive interactions, and various competition avoidance mechanisms besides niche partitioning may facilitate the coexistence of carnivores in Japan. The study also found that the degree of trophic niche overlap varied by season, indicating that shifts in environmental conditions, particularly food abundance and snowfall, may affect potential competitive interactions among carnivore guilds.

A fluorescence sensor for thiram detection based on DNA-templated silver nanoclusters without metal ion-mediator

In this work, we firstly found a strong competitive interaction between thiram and silver atoms of DNA-templated silver nanoclusters (DNA-AgNCs), leading to fluorescence quenching of DNA-AgNCs without additional metal ion-mediator. Furthermore, this thiram-induced fluorescence quenching phenomenon was used to develop a sensor for thiram detection. This fluorescence sensor exhibited good linearity with thiram concentration from 0.20 to 2.0 μM and 0.012–0.20 μM under optimized conditions, with a low detection limit of 0.2 μM and 0.01 μM, respectively. Moreover, this sensor showed superior selectivity towards thiram, and its practicability was verified in apples and soil. This study provides a convenient and rapid “mix and detect” approach for thiram detection within 10 min, suggesting its potential for rapid on-site evaluation of thiram in real samples.

Well-mixed Lotka-Volterra model with random strongly competitive interactions.

The random Lotka-Volterra model is widely used to describe the dynamical and thermodynamic features of ecological communities. In this work, we consider random symmetric interactions between species and analyze the strongly competitive interaction case. We investigate different scalings for the distribution of the interactions with the number of species and try to bridge the gap with previous works. Our results show two different behaviors for the mean abundance at zero and finite temperature, respectively, with a continuous crossover between the two. We confirm and extend previous results obtained for weak interactions: at zero temperature, even in the strong competitive interaction limit, the system is in a multiple-equilibria phase, whereas at finite temperature only a unique stable equilibrium can exist. Finally, we establish the qualitative phase diagrams and compare the species abundance distributions in the two cases.

Temporal Differentiation of Resource Capture and Biomass Accumulation as a Driver of Yield Increase in Intercropping.

Intercropping, i.e., the simultaneous cultivation of different crops on the same field, has demonstrated yield advantages compared to monoculture cropping. These yield advantages have often been attributed to complementary resource use, but few studies quantified the temporal complementarity of nutrient acquisition and biomass production. Our understanding of how nutrient uptake rates of nitrogen (N) and phosphorous (P) and biomass accumulation change throughout the growing season and between different neighbors is limited. We conducted weekly destructive harvests to measure temporal trajectories of N and P uptake and biomass production in three crop species (oat, lupin, and camelina) growing either as isolated single plants, in monocultures or as intercrops. Additionally, we quantified organic acid exudation in the rhizosphere and biological N2-fixation of lupin throughout the growing season. Logistic models were fitted to characterize nutrient acquisition and biomass accumulation trajectories. Nutrient uptake and biomass accumulation trajectories were curtailed by competitive interactions, resulting in earlier peak rates and lower total accumulated nutrients and biomass compared to cultivation as isolated single plants. Different pathways led to overyielding in the two mixtures. The oat–camelina mixture was characterized by a shift from belowground temporal niche partitioning of resource uptake to aboveground competition for light during the growing season. The oat–lupin mixture showed strong competitive interactions, where lupin eventually overyielded due to reliance on atmospheric N and stronger competitiveness for soil P compared to oat. Synthesis: This study demonstrates temporal shifts to earlier peak rates of plants growing with neighbors compared to those growing alone, with changes in uptake patterns suggesting that observed temporal shifts in our experiment were driven by competitive interactions rather than active plant behavior to reduce competition. The two differing pathways to overyielding in the two mixtures highlight the importance of examining temporal dynamics in intercropping systems to understand the underlying mechanisms of overyielding.

Understanding parapatry: How do environment and competitive interactions shape Iberian vipers’ distributions?

ABSTRACTAimAs parapatric distributions are traditionally studied by pairs of species, this study aims to evaluate the causes of the maintenance of parapatry, specifically to assess whether the case of the three viper species present in the Iberian Peninsula is mainly caused by environmental conditions, historical events, interspecific competition among them, or a combination of these factors.LocationThe Iberian Peninsula.TaxonVipera aspis, V. latastei and V. seoanei..MethodsWe applied the concept of favourability of occurrence to produce commensurate distribution units unaffected by the prevalence of different species in the Iberian Peninsula. We compared the favourability of each species individually with the favourability of occurrence of more than one species co‐occurring in their overlapping ranges, and identified the areas in which sympatric coexistence, environmental segregation and competitive exclusion are predicted to occur.ResultsThe main driver of the parapatric pattern was competitive exclusion, which was mediated by gradual changes in the environmental conditions favouring each species. The para‐Mediterranean V. aspis presented fragmented favourable areas outside its range that seemed to be unoccupied due to competitive exclusion by the other vipers. The Mediterranean V. latastei appeared to be limited by competition with the other viper species and by the environment in north‐western Iberia. V. seoanei prevented the other two species becoming established in the north‐western quarter of the Iberian Peninsula due to its better adaption to the humid conditions in this region. Some areas of sustainable coexistence were detected, mainly in the upper reaches of the River Ebro.Main conclusionsEach species is better adapted to particular conditions. However, the existence of ecotones forces them to occur sympatrically and compete for resources. The parapatric pattern is a result of the evolutionary history of the species and of strong competitive interactions between them, which form ‘competitive‐exclusion barriers’. However, these barriers are environmentally dependent, so changes in the environment could rapidly affect the limits of the species distribution.

Directionality and community‐level selection

Many ecological community dynamics display some degree of directionality, known as succession patterns. But complex interaction networks frequently tend to non‐directional dynamics such as chaos, unless additional structures or mechanisms impose some form of, often fragile or shot‐lived, directionality. We exhibit here a novel property of emergent long‐lasting directionality in competitive communities, which relies on very minimal assumptions.We model communities where each species has a few strong competitive interactions, and many weak ones. We find that, at high enough diversity, the dynamics become directional, meaning that the community state can be characterized by a function that increases in time, which we call ‘maturity'. In the presence of noise, the community composition changes toward increasingly stable and productive states. This scenario occupies a middle ground between deterministic succession and purely random species associations: there are many overlapping stable states, with stochastic transitions, that are nevertheless biased in a particular direction. When a spatial dimension is added in the form of a meta‐community, higher‐maturity community states are able to expand in space, replacing others by (exact or approximate) copies of themselves. This leads to community‐level selection, with the same maturity function acting as fitness. Classic concepts from evolutionary dynamics provide a powerful analogy to understand this strictly ecological, community‐level phenomenon of emergent directionality.

Effects of interactions between macroalgae and seagrass on the distribution of macrobenthic invertebrate communities at the Yellow River Estuary, China

Algae-dominance in seagrass beds has been well recognized, however, the competitive relationship between seagrass and macroalgae along land-sea gradients and their ecological effects has received little attention. In this study, a field survey was conducted at the Yellow River Estuary to investigate the effects of macroalgal proliferation on seagrass and macrobenthic invertebrate communities. Our results suggested that strong competitive interaction existed between the two primary producers, and the positive or negative effects of macroalgae on seagrass growth varied along land-sea gradient. Furthermore, the dominant controlling factors on the biomass, density and diversity of macrobenthic invertebrate communities were found to vary accordingly, i.e., from features of the primary producers in the nearshore where macroalgae suppressed seagrass growth to hydrodynamic disturbance in the offshore where macroalgae facilitated seagrass growth. Our study emphasizes the importance to integrate interspecific competition into ecosystem-based management of seagrass ecosystem, and provides references for additional ecological indicators.

Pythons in the Eocene of Europe reveal a much older divergence of the group in sympatry with boas.

Extant large constrictors, pythons and boas, have a wholly allopatric distribution that has been interpreted largely in terms of vicariance in Gondwana. Here, we describe a stem pythonid based on complete skeletons from the early-middle Eocene of Messel, Germany. The new species is close in age to the divergence of Pythonidae from North American Loxocemus and corroborates a Laurasian origin and dispersal of pythons. Remarkably, it existed in sympatry with the stem boid Eoconstrictor. These occurrences demonstrate that neither dispersal limitation nor strong competitive interactions were decisive in structuring biogeographic patterns early in the history of large, hyper-macrostomatan constrictors and exemplify the synergy between phylogenomic and palaeontological approaches in reconstructing past distributions.

Feed competition reduces heritable variation for body weight in Litopenaeus vannamei

BackgroundCompetition is a common social interaction among shrimp and depending on its intensity, it can affect heritable variation and response to selection. Little is known about the variance of indirect genetic effects (IGE) under competitive and non-competitive conditions in shrimp. In this study, we used extended mixed linear models to estimate genetic parameters for the direct genetic effect (DGE) and IGE on body weight in Litopenaeus vannamei raised under ad libitum (AF, non-competitive environment) and restricted (RF, competitive environment) feeding regimes.ResultsEstimates of heritabilities for body weight obtained with a traditional animal model (i.e. without accounting for IGE) were 0.11 ± 0.09 under AF and 0.25 ± 0.11 under RF. With extended animal models that accounted for IGE, the corresponding estimates for body weight were 0.07 ± 0.08 and 0.34 ± 0.11. Thus, heritabilities were higher under the RF regime than under the AF regime, regardless of whether IGE was accounted for or not. The log-likelihood ratio test revealed significant IGE under the RF regime. Although estimates of indirect genetic variance were low (0.0023 ± 0.0013 for AF and 0.0028 ± 0.0012 for RF), they contributed substantially to the total heritable variance: 66.8% for AF and 692.2% for RF. The total heritable variance was smaller under the RF regime (0.7 ± 1.3) than under the AF regime (5.8 ± 2.6) because of the high contribution of the negative covariance between DGE and IGE (− 7.03). Estimates of the correlation between DGE and IGE were 0.32 ± 0.47 under AF and − 0.93 ± 0.15 under RF, those of DGE and IGE for body weight between both regimes were 0.94 ± 0.07 and 0.67 ± 0.20, respectively, and those of IGE for body weight with DGE for survival were − 0.12 ± 0.22 under AF and − 0.58 ± 0.20 under RF.ConclusionsThese results indicate that strong competitive interactions occurred under the RF regime in L. vannamei. Significant reranking and variation in IGE of individuals were observed between the two feeding regimes. Strong competitive interactions reduced the total heritable variation for body weight when food was restricted. These results indicate that the extent of competition among L. vannamei depends on the feeding regime applied and that this competition affects the genetic basis of body weight.

Deep-rooted pigeon pea promotes the water relations and survival of shallow-rooted finger millet during drought-Despite strong competitive interactions at ambient water availability.

Bioirrigation has been defined as the transfer of hydraulically lifted water by a deep-rooted plant to a neighbouring shallow-rooted plant which cannot access deep soil moisture. In this study, we tested if facilitative effects of bioirrigation or the competition for water dominate the interaction of two intercropped plants—deep-rooted pigeon pea (PP) and shallow-rooted finger millet (FM) before and during a drought. Additionally, we tested how the presence of a common mycorrhizal network (CMN) affects the balance between facilitative (i.e. bioirrigation) and competitive interactions between two intercropping species. Our results show that PP can indeed promote the water relations of FM during a drought event. Specifically, stomatal conductance in FM controls dropped to low values of 27.1 to 33.6 mmol m-2s-1, while FM in intercropping treatments were able to maintain its stomatal conductance at 60 mmol m-2s-1. In addition, the presence of PP reduced the drought-induced foliar damage and mortality of FM. The observed facilitative effects of PP on FM were partially enhanced by the presence of a CMN. In contrast to the facilitative effects under drought, PP exerted strong competitive effects on FM before the onset of drought. This hindered growth and biomass production of FM when intercropped with PP, an effect that was even enhanced in the presence of a CMN. The results from our study thus indicate that in intercropping, deep-rooted plants may act as "bioirrigators" for shallow-rooted crops and that a CMN can promote these facilitative effects. However, the interspecific competition between the intercropped plants under conditions of abundant moisture supply can be strong and are enhanced by the presence of a CMN. In more general terms, our study shows that the extent by which the antagonistic effects of facilitation and competition are expressed in an intercropping system strongly depends on the availability of resources, which in the case of the present study was water and the presence of biotic interactions (i.e. the presence of a CMN).

High-order interactions distort the functional landscape of microbial consortia.

Understanding the link between community composition and function is a major challenge in microbial population biology, with implications for the management of natural microbiomes and the design of synthetic consortia. Specifically, it is poorly understood whether community functions can be quantitatively predicted from traits of species in monoculture. Inspired by the study of complex genetic interactions, we have examined how the amylolytic rate of combinatorial assemblages of six starch-degrading soil bacteria depend on the separate functional contributions from each species and their interactions. Filtering our results through the theory of biochemical kinetics, we show that this simple function is additive in the absence of interactions among community members. For about half of the combinatorially assembled consortia, the amylolytic function is dominated by pairwise and higher-order interactions. For the other half, the function is additive despite the presence of strong competitive interactions. We explain the mechanistic basis of these findings and propose a quantitative framework that allows us to separate the effect of behavioral and population dynamics interactions. Our results suggest that the functional robustness of a consortium to pairwise and higher-order interactions critically affects our ability to predict and bottom-up engineer ecosystem function in complex communities.

Defining Higher-Order Interactions in Synthetic Ecology: Lessons from Physics and Quantitative Genetics.

A new paper from Mickalide and Kuehn studies a well-controlled microbial trophic chain and identifies a high-order interaction between its species.

Direct and indirect effects of flood regime on macroinvertebrate assemblages in a floodplain riverscape

AbstractFloods are necessary for the functioning of floodplain ecosystems. Ultimately, flood effects on biota are spatially complex and unfold at various time scales. Yet, biodiversity conservation in regulated floodplains requires a sound quantification of the main pathways how floods affect riverine ecosystems. Here, we investigated the relative effects of flood frequency, magnitude, and time elapsed since the last flood on macroinvertebrate communities of 24 parafluvial habitats in the Maggia river floodplain, Switzerland. Parafluvial habitats were sampled seasonally over 1 year, and a combination of 2D hydrodynamic modelling and piecewise structural equation modelling was used to quantify the direct and indirect effects of local hydrological metrics on macroinvertebrate communities. We found that high flood frequency favoured rheophilic species (EPT taxa) over other groups (Coleoptera, Diptera) and prevented strong competitive interactions and competitive exclusion by maintaining low food resource levels. Importantly, we found that parafluvial habitats exhibited more lentic‐like characteristics as time passed after a flood, which caused EPT taxa to be relatively more abundant and taxa richness higher immediately after flood disturbance. Lastly, overall taxa richness increased over time after a flood and even more so after larger floods. Our results suggest that variation in flood magnitude, frequency, and return period maximizes beta diversity within floodplain riverscapes due to the independent and spatially interactive responses of parafluvial habitats.

When can competition and dispersal lead to checkerboard distributions?

Checkerboard distributions-mutually exclusive species co-occurrences-are a common observation in community ecology and biogeography. While the underlying causes of checkerboard distributions have remained elusive, a long-standing argument is that they are representative of strong competitive interactions and/or dispersal limitation. We explore this using a stochastic two-patch metacommunity model combined with an experimental two-patch system of competing Tribolium species, quantifying checkerboard distributions using the abundance-based index Ast . We find that maintenance of checkerboard distributions is possible in a limited parameter space consisting of low dispersal rates, low population growth rates and high interspecific competition. Checkerboards were not maintained in experimental metacommunities. Our model, parameterized using independent data, echoed this finding, providing a clear link between model and experiment, and suggested that only small regions of parameter space would allow for checkerboard distributions between patches with equally hospitable environments. These findings may provide insight into when interspecific competition and dispersal limitation would promote checkerboard distributions.

Food Web Structure Informs Potential Causes of Bimodal Size Structure in a Top Predator

Background: Assemblages of fishes in lakes and reservoirs in the western USA are dominated by non-native, large-bodied, piscivorous fishes that lack a shared evolutionary history. Top predators in these crowded systems are often characterized by unstable population dynamics and poor somatic growth rates. One such assemblage is in Fish Lake, located in southern Utah, USA, in which introduced lake trout (Salvelinus namaycush, Walbaum) exhibit a bimodal growth pattern. A few lake trout in Fish Lake grow rapidly to large size typical of the species; whereas, most never grow beyond 600 mm total length. Objective: To inform competitive interactions in this evolutionarily novel fish assemblage that might cause the low recruitment to large body size in lake trout, we characterized trophic niche (from stable isotope analysis of C and N) of all fishes in the lake. Methods: We used a Bayesian mixing model to describe the trophic niche and infer diet of lake trout and their potential prey, and we used Bayesian ellipse analysis to identify potential areas of high competition within the food web. Large lake trout feed mostly on small lake trout and splake (Salvelinus namaycush, Walbaum x Salvelinus fontinalis, Mitchill) despite availability of abundant yellow perch. (Perca flavescens, Mitchill). Small lake trout and splake feed mostly on zooplankton and exhibit substantial overlap of their trophic niche implying competition for food. Yellow perch and Utah chub (Gila atraria, Girard; formerly an important food item for lake trout in Fish Lake) exhibit extreme overlap of their trophic niche implying strong competitive interactions. Results: Our data suggest that lack of recruitment to large body size in lake trout may result from a reduction in availability of Utah chub resulting from competitive interactions with yellow perch, and increased competition from introduced splake for available prey. Conclusion: Management actions that may help ameliorate the poor somatic growth rates of most lake trout include efforts to reduce perch populations or increase vulnerability of perch to predation by lake trout, and removal of splake as a competitor of small lake trout.

A Combined Theoretical and Experimental Study of CH3NH3PbI3 Containing AVAI Films Prepared via an Intramolecular Exchange Process

Methylammonium lead iodide (CH3NH3PbI3) has emerged as a superior light-absorbing material for perovskite solar cells, mainly because of its excellent optical and electronic properties. However, insufficient long-term stability of CH3NH3PbI3 has severely hindered its practical applications. The direct addition of 5-ammonium valeric acid iodide (HOOC(CH2)4NH3I or AVAI) to perovskite precursors, such as CH3NH3I and PbI2, was found to improve the stability of CH3NH3PbI3, but can limit the incorporation of AVA+ into the CH3NH3PbI3 structure because of strong competitive interactions between AVA+ and CH3NH3+ with PbI2 through the same electrostatic interactions. Here, we present an alternative approach to prepare high-quality CH3NH3PbI3 containing AVAI films via an intramolecular exchange process. The films were prepared from precursor complexes, that is, organic lead iodide complexes, by the intramolecular exchange of dimethyl sulfoxide intercalated in the complexes with CH3NH3+. Scanning electron microscopy,...