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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. [ABSTRACT FROM AUTHOR]

The deliberate release of captive‐bred individuals, the accidental escape of domesticated strains, or the invasion of closely related conspecifics into wild populations can all lead to introgressive hybridization, which poses a challenge for conservation and wildlife management. Rates of introgression and the magnitude of associated demographic impacts vary widely across ecological contexts. However, the reasons for this variation remain poorly understood. One rarely considered phenomenon in this context is soft selection, wherein relative trait values determine success in intraspecific competition for a limiting resource. Here we develop an eco‐genetic model explicitly focussed on understanding the influence of such competitive interactions on the eco‐evolutionary dynamics of wild populations experiencing an influx of foreign/domesticated individuals. The model is applicable to any taxon that experiences natural or human‐mediated inputs of locally maladapted genotypes ('intrusion'), in addition to phenotype‐dependent competition for a limiting resource (e.g. breeding sites, feeding territories). The effects of both acute and chronic intrusion depended strongly on the relative competitiveness of intruders versus locals. When intruders were competitively inferior, density‐dependent regulation limited their reproductive success (ability to compete for limited spawning sites), which prevented strong introgression or population declines from occurring. In contrast, when intruders were competitively superior, this amplified introgression and led to increased maladaptation of the admixed population. This had negative consequences for population size and population viability. The results were sensitive to the intrusion level, the magnitude of reproductive excess, trait heritability and the extent to which intruders were maladapted relative to locals. Our findings draw attention to under‐appreciated interactions between phenotype‐dependent competitive interactions and maladaptive hybridization, which may be critical to determining the impact captive breeding programmes and domesticated escapees can have on otherwise self‐sustaining wild populations. [ABSTRACT FROM AUTHOR]

For both government and private institutions, the development of collaboration networks becomes an element of great importance for the implementation of related policies such as the circular economy and sustainable practices in manufacturing. Despite the above, such initiatives have not received as much attention in literature but have been decisive as both public and private initiatives. Initiatives in Latin America do not escape this scenario, especially in the creation of conditions that allow the promotion of approaches such as industrial symbiosis. In this way, the present research is aimed at identifying the role of trophic, mutualistic, and competitive interactions in an industrial symbiosis process implementation. A network analysis model is used to achieve this purpose. This technique allows us to know the degree of importance of the different actors that are part of a network, as well as the factors that determine the implementation of initiatives such as industrial symbiosis. Among the results are that empirical findings confirm the presence of trophic interactions that enhance resource efficiency, mutualistic interactions fostering collaboration and synergy, and competitive interactions promoting efficiency and dynamism. Additionally, a green culture, business size, and innovation activities are revealed as influential factors amplifying network dynamics. [ABSTRACT FROM AUTHOR]

Ecological similarity plays an important role in biotic interactions. Increased body size similarity of competing species, for example, increases the strength of their biotic interactions. Body sizes of many exothermic species are forecast to be altered under global warming, mediating shifts in existing trophic interactions among species, in particular for species with different thermal niches.Temperate rocky reefs along the southeast coast of Australia are located in a climate warming hotspot and now house a mixture of temperate native fish species and poleward range‐extending tropical fishes (vagrants), creating novel species assemblages. Here, we studied the relationship between body size similarity and trophic overlap between individual temperate native and tropical vagrant fishes.Dietary niche overlap between vagrant and native fish species increased as their body sizes converged, based on both stomach content composition (short‐term diet), stable isotope analyses (integrated long‐term diet) and similarity in consumed prey sizes.We conclude that the warming‐induced faster growth rates of tropical range‐extending fish species at their cool water ranges will continue to converge their body size towards and strengthen their degree of trophic interactions and dietary overlap with co‐occurring native temperate species under increasing ocean warming. The strengthening of these novel competitive interactions is likely to drive changes to temperate food web structures and reshuffle existing species community structures. [ABSTRACT FROM AUTHOR]

Weed communities influence the dynamics of ecosystems, particularly in disturbed environments where anthropogenic activities often result in higher pollution. Understanding the dynamics existing between native weed communities and invasive species in disturbed environments is crucial for effective management and normal ecosystem functioning. Recognising the potential resistance of native weed communities to invasion in disturbed environments can help identify suitable native plants for restoration operations. This review aims to investigate the adaptations exhibited by native and non‐native weeds that may affect invasions within disturbed environments. Factors such as ecological characteristics, altered soil conditions, and adaptations of native weed communities that potentially confer a competitive advantage relative to non‐native or invasive weeds in disturbed environments are analysed. Moreover, the roles of biotic interactions such as competition, mutualistic relationships, and allelopathy in shaping the invasion resistance of native weed communities are described. Emphasis is given to the consideration of the resistance of native weeds as a key factor in invasion dynamics that provides insights for conservation and restoration efforts in disturbed environments. Additionally, this review underscores the need for further research to unravel the underlying mechanisms and to devise targeted management strategies. These strategies aim to promote the resistance of native weed communities and mitigate the negative effects of invasive weed species in disturbed environments. By delving deeper into these insights, we can gain an understanding of the ecological dynamics within disturbed ecosystems and develop valuable insights for the management of invasive species, and to restore long‐term ecosystem sustainability. [ABSTRACT FROM AUTHOR]

Navua sedge (Cyperus aromaticus), a perennial plant native to Africa, poses a significant weed concern due to its capacity for seed and rhizome fragment dissemination. Infestations can diminish pasture carrying capacity, displacing desirable species. Despite the burgeoning interest in integrated weed management strategies, information regarding the efficacy of competitive interactions with other pasture species for Navua sedge management remains limited. A pot trial investigated the competitive abilities of 14 diverse broadleaf and grass pasture species. The results indicated a range of the reduction in Navua sedge dry biomass from 6% to 98% across these species. Subsequently, three broadleaf species—burgundy bean (Macroptilium bracteatum), cowpea (Vigna unguiculata), and lablab (Lablab purpureus), and three grass species—Gatton panic (Megathyrsus maximus), Rhodes grass (Chloris gayana), and signal grass (Urochloa decumbens) were chosen for a follow-up pot trial based on their superior dry biomass performance. These six species were planted at three varying densities (44, 88, and 176 plants/m2) surrounding a Navua sedge plant. Among the grass pasture species, Gatton panic and Rhodes grass exhibited high competitiveness, resulting in a minimum decrease of 86% and 99%, respectively, in Navua sedge dry biomass. Regarding the broadleaf species, lablab displayed the highest competitiveness, causing a minimum decrease of 99% in Navua sedge dry biomass. This study highlights the increasing efficacy of crop competition in suppressing weed growth and seed production, with the most significant suppression observed at a density of 176 plants/m2. [ABSTRACT FROM AUTHOR]

Interactions between two plant species can be influenced by the presence of other plant species and such an effect may change as the diversity of the other species increases. To test these hypotheses, we first constructed aquatic communities consisting of 1, 2 and 4 emergent plant species and then grew ramets of Lemna minor only, ramets of Spirodela polyrhiza only or ramets of both L. minor and S. polyrhiza within these aquatic communities. We also included controls with ramets of L. minor , S. polyrhiza or both but without any emergent plants. Biomass and number of ramets of L. minor and S. polyrhiza were significantly smaller with than without the emergent plants, but they did not differ among the three richness levels. The presence of S. polyrhiza did not significantly affect the growth of L. minor , and such an effect was not dependent on the richness of the emergent plant species. Without the emergent plant species, the presence of L. minor markedly reduced biomass (−92%) and number of ramets (−88%) of S. polyrhiza. However, such a competitive effect of L. minor on S. polyrhiza became much weaker in the presence of one emergent plant species (−46% biomass and −39% number of ramets) and completely disappeared in the presence of two or four emergent plant species. Therefore, both the presence and richness of emergent plant species can alter competitive interactions between the two duckweed species. These findings highlight the importance of species diversity in regulating plant–plant interactions. [ABSTRACT FROM AUTHOR]

Understanding the competition and coexistence of flagship carnivores is key to creating strategies for their conservation in the face of global carnivore declines. Although studies exploring the dynamics and competition between tigers (Panthera tigris) and leopards (P. pardus) span decades, there is a lack of understanding regarding the factors that influence their coexistence mechanisms on a broad scale, as well as the drivers determining their exploitative and interference competition. We gathered a comprehensive list of research papers among which 36 papers explored the interspecific interactions between tigers and leopards and tested the influence of biotic and abiotic factors on the coexistence mechanisms along three dimensions using multiple response variables regression models; we also tested the influence of ecological drivers determining the exploitative or interference competition between tigers and leopards. Elevation and ungulate density were the most important predictors in regulating the coexistence mechanisms. Tigers and leopards exhibited more positive relations/higher overlaps as elevation increased in the spatial niche. In addition, they showed a higher dietary overlap in the prey‐rich regions. We determined that interference competition between tigers and leopards was less frequently observed in habitats with dense tree cover and homogeneous vegetation structures. Meanwhile, studies with multiple metrics would promote the detection of interference competition. Our study provides new insight into the competitive interactions and coexistence mechanisms of tigers and leopards on a broad scale. Policy‐makers and managers should pay more attention to the factors of elevation, prey abundance, and habitat structures for the conservation of tigers and leopards. [ABSTRACT FROM AUTHOR]

Abstract The deliberate release of captive‐bred individuals, the accidental escape of domesticated strains, or the invasion of closely related conspecifics into wild populations can all lead to introgressive hybridization, which poses a challenge for conservation and wildlife management. Rates of introgression and the magnitude of associated demographic impacts vary widely across ecological contexts. However, the reasons for this variation remain poorly understood. One rarely considered phenomenon in this context is soft selection, wherein relative trait values determine success in intraspecific competition for a limiting resource. Here we develop an eco‐genetic model explicitly focussed on understanding the influence of such competitive interactions on the eco‐evolutionary dynamics of wild populations experiencing an influx of foreign/domesticated individuals. The model is applicable to any taxon that experiences natural or human‐mediated inputs of locally maladapted genotypes (‘intrusion’), in addition to phenotype‐dependent competition for a limiting resource (e.g. breeding sites, feeding territories). The effects of both acute and chronic intrusion depended strongly on the relative competitiveness of intruders versus locals. When intruders were competitively inferior, density‐dependent regulation limited their reproductive success (ability to compete for limited spawning sites), which prevented strong introgression or population declines from occurring. In contrast, when intruders were competitively superior, this amplified introgression and led to increased maladaptation of the admixed population. This had negative consequences for population size and population viability. The results were sensitive to the intrusion level, the magnitude of reproductive excess, trait heritability and the extent to which intruders were maladapted relative to locals. Our findings draw attention to under‐appreciated interactions between phenotype‐dependent competitive interactions and maladaptive hybridization, which may be critical to determining the impact captive breeding programmes and domesticated escapees can have on otherwise self‐sustaining wild populations.

Investigating how climate change alters selection regimes is a crucial step toward understanding the potential of populations to evolve in the face of changing conditions. Previous studies have mainly focused on understanding how changing climate directly influences selection, while the role of species' interactions has received little attention. Here, we used a transplant experiment along an elevation gradient to estimate how climate warming and competitive interactions lead to shifts in directional phenotypic selection on morphology and phenology of four alpine plants. We found that warming generally imposed novel selection, with the largest shifts in regimes acting on specific leaf area and flowering time across species. Competitors instead weakened the selection acting on traits that was imposed directly by warming. Weakened or absent selection in the presence of competitors was largely associated with the suppression of absolute means and variation of fitness. Our results suggest that although climate change can impose strong selection, competitive interactions within communities might act to limit selection and thereby stymie evolutionary responses in alpine plants facing climate change. [ABSTRACT FROM AUTHOR]

Closely related species with ecological similarity often aggressively compete for a common, limited resource. This competition is usually asymmetric and results in one species being behaviorally dominant over the other. Trade-offs between traits for behavioral dominance and alternative strategies can result in different methods of resource acquisition between the dominant and subordinate species, with important consequences for resource partitioning and community structure. Body size is a key trait thought to commonly determine behavioral dominance. Priority effects (i.e., which species arrives at the resource first), however, can also determine the outcome of interactions, as can species-specific traits besides size that give an advantage in aggressive contests (e.g., weapons). Here, we test among these three alternative hypotheses of body size, priority effects, and species identity for what determines the outcome of competitive interactions among two species of burying beetles, Nicrophorus orbicollis and N. pustulatus. Both overlap in habitat and seasonality and exhibit aggressive competition over a shared breeding resource of small vertebrate carrion. In trials, we simulated what would happen upon the beetles' discovery of a carcass in nature by placing a carcass and one beetle of each species in a container and observing interactions over 13 h trials (n = 17 trials). We recorded and categorized interactions between beetles and the duration each individual spent in contact with the carcass (the key resource) to determine which hypothesis predicted trial outcomes. Body size was our only significant predictor; the largest species won most aggressive interactions and spent more time in contact with the carcass. Our results offer insight into the ecology and patterns of resource partitioning of N. orbicollis and N. pustulatus, the latter of which is unique among local Nicrophorus for being a canopy specialist. N. pustulatus is also unique among all Nicrophorus in using snake eggs, in addition to other carrion, as a breeding resource. Our results highlight the importance of body size and related trade-offs in ecology and suggest parallels with other coexisting species and communities. [ABSTRACT FROM AUTHOR]

Navua sedge (Cyperus aromaticus), a perennial plant native to Africa, poses a significant weed concern due to its capacity for seed and rhizome fragment dissemination. Infestations can diminish pasture carrying capacity, displacing desirable species. Despite the burgeoning interest in integrated weed management strategies, information regarding the efficacy of competitive interactions with other pasture species for Navua sedge management remains limited. A pot trial investigated the competitive abilities of 14 diverse broadleaf and grass pasture species. The results indicated a range of the reduction in Navua sedge dry biomass from 6% to 98% across these species. Subsequently, three broadleaf species—burgundy bean (Macroptilium bracteatum), cowpea (Vigna unguiculata), and lablab (Lablab purpureus), and three grass species—Gatton panic (Megathyrsus maximus), Rhodes grass (Chloris gayana), and signal grass (Urochloa decumbens) were chosen for a follow-up pot trial based on their superior dry biomass performance. These six species were planted at three varying densities (44, 88, and 176 plants/m2) surrounding a Navua sedge plant. Among the grass pasture species, Gatton panic and Rhodes grass exhibited high competitiveness, resulting in a minimum decrease of 86% and 99%, respectively, in Navua sedge dry biomass. Regarding the broadleaf species, lablab displayed the highest competitiveness, causing a minimum decrease of 99% in Navua sedge dry biomass. This study highlights the increasing efficacy of crop competition in suppressing weed growth and seed production, with the most significant suppression observed at a density of 176 plants/m2.

Closely related species with ecological similarity often aggressively compete for a common, limited resource. This competition is usually asymmetric and results in one species being behaviorally dominant over the other. Trade-offs between traits for behavioral dominance and alternative strategies can result in different methods of resource acquisition between the dominant and subordinate species, with important consequences for resource partitioning and community structure. Body size is a key trait thought to commonly determine behavioral dominance. Priority effects (i.e., which species arrives at the resource first), however, can also determine the outcome of interactions, as can species-specific traits besides size that give an advantage in aggressive contests (e.g., weapons). Here, we test among these three alternative hypotheses of body size, priority effects, and species identity for what determines the outcome of competitive interactions among two species of burying beetles, Nicrophorus orbicollis and N. pustulatus. Both overlap in habitat and seasonality and exhibit aggressive competition over a shared breeding resource of small vertebrate carrion. In trials, we simulated what would happen upon the beetles’ discovery of a carcass in nature by placing a carcass and one beetle of each species in a container and observing interactions over 13 h trials (n = 17 trials). We recorded and categorized interactions between beetles and the duration each individual spent in contact with the carcass (the key resource) to determine which hypothesis predicted trial outcomes. Body size was our only significant predictor; the largest species won most aggressive interactions and spent more time in contact with the carcass. Our results offer insight into the ecology and patterns of resource partitioning of N. orbicollis and N. pustulatus, the latter of which is unique among local Nicrophorus for being a canopy specialist. N. pustulatus is also unique among all Nicrophorus in using snake eggs, in addition to other carrion, as a breeding resource. Our results highlight the importance of body size and related trade-offs in ecology and suggest parallels with other coexisting species and communities.

In this paper, we investigate the prespecified-time bipartite synchronization (PTBS) of coupled reaction-diffusion memristive neural networks (CRDMNNs) with both competitive and cooperative interactions. Two types of bipartite synchronization are considered: leaderless PTBS and leader-following PTBS. With the help of a structural balance condition, the criteria for PTBS for CRDMNNs are derived by designing suitable Lyapunov functionals and novel control protocols. Different from the traditional finite-time or fixed-time synchronization, the settling time obtained in this paper is independent of control gains and initial values, which can be pre-set according to the task requirements. Lastly, numerical simulations are given to verify the obtained results.

Cellulose nanocrystals (CNCs) were extracted from bleached cotton by sulfuric acid hydrolysis. Thin films were prepared from the aqueous suspension of CNCs by casting and evaporation with 15% glycerol as a plasticizer. Our research aimed to create stable films resistant to water. The structure and the interactions of the films were modified by short (10 min) heating at different temperatures (100, 140, and 160 °C) and by adding different amounts of citric acid (0, 10, 20, and 30%). Various analytical methods were used to determine the structure, surface properties, and mechanical properties. The interaction of composite films with water and water vapor was also investigated. Heat treatment did not significantly affect the film properties. Citric acid, without heat treatment, acted as a plasticizer. It promoted the disintegration of films in water, increased water vapor sorption, and reduced tensile strength, resulting in flexible and easy-to-handle films. The combination of heat treatment and citric acid resulted in stable liquid-water-resistant films with excellent mechanical properties. A minimum heating temperature of 120 °C and a citric acid concentration of 20% were required to obtain a stable CNC film structure resistant to liquid water. [ABSTRACT FROM AUTHOR]

The green alga Caulerpa cylindracea Sonder (Chlorophyta; Bryopsidales) is one of the most invasive alien macroalgae in the Mediterranean Sea, where it is also spreading on rhodolith beds, an important biogenic assemblage typical of deep substrates. Despite the importance of rhodoliths, data on the competitive interactions with C. cylindracea are still scarce. To deepen the knowledge on the topic, C. cylindracea occurrence on the rhodolith bed of Capo Carbonara Marine Protected Area (Italy) was explored. Quantitative analyses of videoframes obtained from Remote Operated Vehicle records in three different MPA sites, Is Piscadeddus, Santa Caterina, and Serpentara, allow for estimates of both the cover of rhodoliths (considering the main morphotypes) and of C. cylindracea, as well as their competition. All sites showed a well-developed rhodolith bed, although some differences were highlighted in their composition in terms of morphotype, shape, and dimension of rhodoliths, as well as in the C. cylindracea cover. In particular, Santa Caterina appeared to be the site with the highest mean total cover of rhodoliths (68%), and of C. cylindracea (25%). The obtained results suggest that different competitive interactions occur between C. cylindracea and rhodolith beds, in relation to the morphostructural composition of the latter and in response to environmental conditions that affect rhodolith bed composition. [ABSTRACT FROM AUTHOR]

Competitive interactions between native and nonindigenous species occur under conditions of ongoing environmental alterations related to urbanization and climate change, presenting a challenge to understanding invasiveness. Indigenous submerged aquatic vegetation species have been negatively impacted by nutrient enrichment and saltwater intrusion, while simultaneously experiencing a rapid spread in nonindigenous competitors. To better predict future shifts in freshwater macrophyte community dominance, investigations need to consider how these multiscale disturbances influence competitiveness of nonindigenous macrophytes. Using an outdoor greenhouse mesocosm setup for approximately 19 weeks over the course of subtropical winter, we experimentally examined how nutrient enrichment, salinity, and the interaction of both factors influence the competitive interactions between a native macrophyte with moderate salinity tolerance, wild celery (Vallisneria americana), and a highly invasive macrophyte with lower salinity tolerance, hydrilla (Hydrilla verticillata). We tested the factors of macrophyte composition (hydrilla monoculture, wild celery monoculture, or biculture), salinity (0, 4, or 8), and fertilization (ambient or fertilized) on biomass production, biomass allocation, and morphological metrics as responses to environmental condition and interspecific competition. Fertilizer enhanced wild celery leaf area (more than twofold) and shifted allocation toward aboveground biomass, but did not enhance hydrilla competitiveness. Salinity negatively affected wild celery leaf area (by 7.5%–67.8%) and biomass (by 4%–15%) and also reduced hydrilla belowground biomass production (by 6%–25%) but did not influence competition. An interaction effect of fertilizer and salinity negatively influenced hydrilla growth, however the combined factors did not influence competitive outcomes. The lack of evidence for a competitive advantage by hydrilla in this study demonstrates that salinity exposure sufficiently limits a highly invasive plant's competitive abilities and subsequent suppression of a native species. [ABSTRACT FROM AUTHOR]

Information on the structural organization of forest stands obtained on sample plots is the basis for long-term monitoring of post-fire pine forest structure and dynamics in the European North-East. These data can be used as a marker of native pine stands of the European taiga. Here, we studied vertical and horizontal structure in the post-pyrogenic pine forests of Vacciniosum, Vaccinioso-cladinosum and Myrtillosum site types in the boreal forest of the Komi Republic. The type of horizontal structure of uneven-aged forest stands changed with age from grouped to random one. Large trees were randomly distributed on the plot. We observed the weak aggregation of undergrowth trees (natural tree regeneration) in stands at distances of 2-6 m. Undergrowth individuals were characterized by group distribution at smaller distances than 1-2 m. Spatial relationships between large, small and codominant trees demonstrated random distribution in most cases. Undergrowth individuals did not show any competitive relations. However, we revealed a "taking off" effect between mature trees of pine and pine undergrowth. The direction of the displacement of tree crown centre projections relative to the bases of their trunks was ambiguous. The shift of the crown space towards the maximum solar radiation was detected in a thinned stand with old age and big size of trees. In other site types, no one-sided orientation of the tree crown development emerged.

Understanding the mechanisms of species coexistence has always been a fundamental topic in ecology. Classical theory predicts that interspecific competition may select for traits that stabilize niche differences, although recent work shows that this is not strictly necessary. Here, we ask whether adaptive phenotypic plasticity could allow species coexistence (i.e., some stability at an equilibrium point) without ecological differentiation in habitat use. We used individual-based stochastic simulations defining a landscape composed of spatially uncorrelated or autocorrelated environmental patches, where two species with the same competitive strategies, not able to coexist without some form of phenotypic plasticity, expanded their ranges in the absence of a competition—colonization trade-off (a well-studied mechanism for species diversity). Each patch is characterized by a random environmental value that determines the optimal phenotype of its occupants. In such a scenario, only local adaptation and gene flow (migration) may interact to promote genetic variation and coexistence in the metapopulation. Results show that a competitively inferior species with adaptive phenotypic plasticity can coexist in a same patch with a competitively superior, non-plastic species, provided the migration rates and variances of the patches' environmental values are sufficiently large.

Abstract Competitive interactions between native and nonindigenous species occur under conditions of ongoing environmental alterations related to urbanization and climate change, presenting a challenge to understanding invasiveness. Indigenous submerged aquatic vegetation species have been negatively impacted by nutrient enrichment and saltwater intrusion, while simultaneously experiencing a rapid spread in nonindigenous competitors. To better predict future shifts in freshwater macrophyte community dominance, investigations need to consider how these multiscale disturbances influence competitiveness of nonindigenous macrophytes. Using an outdoor greenhouse mesocosm setup for approximately 19 weeks over the course of subtropical winter, we experimentally examined how nutrient enrichment, salinity, and the interaction of both factors influence the competitive interactions between a native macrophyte with moderate salinity tolerance, wild celery (Vallisneria americana), and a highly invasive macrophyte with lower salinity tolerance, hydrilla (Hydrilla verticillata). We tested the factors of macrophyte composition (hydrilla monoculture, wild celery monoculture, or biculture), salinity (0, 4, or 8), and fertilization (ambient or fertilized) on biomass production, biomass allocation, and morphological metrics as responses to environmental condition and interspecific competition. Fertilizer enhanced wild celery leaf area (more than twofold) and shifted allocation toward aboveground biomass, but did not enhance hydrilla competitiveness. Salinity negatively affected wild celery leaf area (by 7.5%–67.8%) and biomass (by 4%–15%) and also reduced hydrilla belowground biomass production (by 6%–25%) but did not influence competition. An interaction effect of fertilizer and salinity negatively influenced hydrilla growth, however the combined factors did not influence competitive outcomes. The lack of evidence for a competitive advantage by hydrilla in this study demonstrates that salinity exposure sufficiently limits a highly invasive plant's competitive abilities and subsequent suppression of a native species.

Organisms from higher tropical levels (e.g., herbivores) can mediate indirect competitive interactions between two target plant species, but such apparent competition may also be mediated by a third plant species and thus may vary depending on the size and competitive ability of the target plant species and the third plant species. We set up an outdoor experiment with four aquatic plant species with similar niches but differing greatly in size, i.e., Lemna minor (the smallest), Spirodela polyrhiza (the second smallest), Salvinia natans (the second largest) and Pistia stratiotes (the largest). We grew L. minor and S. polyrhiza alone or in mixture and in the absence of any third plant species, in the presence of a small, third species S. natans or in the presence of a large, third species P. stratiotes. In the absence of the third species or in the presence of S. natans, the growth of L. minor was greatly inhibited by S. polyrhiza, but in the presence of P. stratiotes, the inhibiting effects of S. polyrhiza disappeared completely and the growth of L. minor greatly increased. By contrast, the presence of L. minor had no effect on the growth of S. polyrhiza, and this effect did not depend on the presence or absence of the third plant species, although the presence of the third species, particularly P. stratiotes, decreased its growth. We conclude that the presence of a third plant species can regulate plant-plant interactions, but such an impact depends on the size and competitive ability of the competing species as well as the third species. Our findings highlight the role of complexity in plant-plant interactions, and suggest that apparent competition between plants can also occur at the same trophic level. These results have important implications for the explanations of species coexistence and biodiversity maintenance.

Information on the structural organization of forest stands obtained on sample plots is the basis for long- -term monitoring of post-fire pine forest structure and dynamics in the European North-East. These data can be used as a marker of native pine stands of the European taiga. Here, we studied vertical and horizontal structure in the post-pyrogenic pine forests of Vacciniosum, Vaccinioso-cladinosum and Myrtillosum site types in the boreal forest of the Komi Republic. The type of horizontal structure of uneven-aged forest stands changed with age from grouped to random one. Large trees were randomly distributed on the plot. We observed the weak aggregation of undergrowth trees (natural tree regeneration) in stands at distances of 2–6 m. Undergrowth individuals were characterized by group distribution at smaller distances than 1–2 m. Spatial relationships between large, small and codominant trees demonstrated random distribution in most cases. Undergrowth individuals did not show any competitive relations. However, we revealed a “taking off” effect between mature trees of pine and pine undergrowth. The direction of the displacement of tree crown centre projections relative to the bases of their trunks was ambiguous. The shift of the crown space towards the maximum solar radiation was detected in a thinned stand with old age and big size of trees. In other site types, no one-sided orientation of the tree crown development emerged. [ABSTRACT FROM AUTHOR]

Abstract Background An ecological approach for managing biological invasions in agroecosystems is the selection of alternative crop species to manage the infestation of invasive alien plants through competition. In the current study, plant growth, photosynthesis, and competitive ability of the crop Helianthus tuberosus L. (Jerusalem artichoke) and the invasive alien plant Ageratina adenophora (Spreng.) R. M. King and H. Rob were compared under varying shade levels by utilizing a de Wit replacement series method. We hypothesized that H. tuberosus had higher competitive ability than A. adenophora even under shaded conditions. Results The results showed the main stem, leafstalk length, leaf area, underground biomass, and aboveground biomass of A. adenophora were significantly lower compared to H. tuberosus in monoculture although A. adenophora had a greater number of branches that were longer on average. Under full sunlight, the total shoot length (stem + branch length), main stem length and branch length of A. adenophora were significantly suppressed (P

Investigation was carried out in virgin spruce forests in the upper reaches of the Pechora river in middle taiga condition. It was show that spruce forests of different types are characterized by common features of the structure of stands and undergrowth. There was a large variability of trees in volume of stem and undergrowth height. Investigated stands formed a cyclical-multi-age type of age structure. The calculated data obtained using spatial statistics and analyses of point processes were presented. It was found that in spruce forests is expressed regardless of forest types, the group distribution of young individuals of woody plants, which passes into random distribution at more late stages of generation. The spatial relationships between woody plants tested using the cross-correlation function gij(r) show that the undergrowth is attracted to each other at distances of up to 1 meter. There were no spatial interrelation between the undergrowth and the trees. Trees demonstrated independent from each other placement in the area. The density of trees in the area and their phytosocial status are determining the intensity of competitive relations between woody plants in the indigenous spruce communities of the upper reaches of the Pechora River.

Environmental heterogeneity of various kinds can promote species coexistence. We hypothesized that greater genetic diversity of a competitively dominant species in a plant community can promote coexistence of subordinate species. To test this hypothesis, we grew the duckweeds Lemna minor and Spirodela polyrhiza apart and together without or with 1, 2, and 4 genotypes of a much larger, co-occurring species, Hydrocotyle verticillata. The presence of H. verticillata strongly reduced the growth of both duckweed species, consistent with its dominance. The presence of S. polyrhiza significantly increased biomass of L. minor and this effect did not depend on the presence or absence of H. verticillata or its genotypic richness. Without H. verticillata , the presence of L. minor drastically reduced biomass (-94%) of S. polyrhiza. However, the inhibitory effect of L. minor on S. polyrhiza became much weaker in the presence of one and two genotypes of H. verticillata and completely disappeared in the presence of four genotypes of H. verticillata. These results suggest that both the presence of H. verticillata and its genotypic richness can alter interspecific interactions between the two duckweed species. We conclude that genetic diversity of a single, highly dominant species may promote coexistence of subordinate species when they differ strongly in the ability to compete with each other. We suggest testing further for effects of genetic diversity of dominant species on subordinate species with similar competitive abilities. • Lemna minor inhibited Spirodela polyrhiza without Hydrocotyle verticillata. • This inhibiting effect became weaker with one genotype of Hydrocotyle. • The inhibiting effect disappeared with 2 or 4 genotypes of Hydrocotyle. • Genetic diversity alters competitive interactions between two target species. • Genetic diversity of dominant species facilitates subordinate species coexistence. [ABSTRACT FROM AUTHOR]

The green alga Caulerpa cylindracea Sonder (Chlorophyta; Bryopsidales) is one of the most invasive alien macroalgae in the Mediterranean Sea, where it is also spreading on rhodolith beds, an important biogenic assemblage typical of deep substrates. Despite the importance of rhodoliths, data on the competitive interactions with C. cylindracea are still scarce. To deepen the knowledge on the topic, C. cylindracea occurrence on the rhodolith bed of Capo Carbonara Marine Protected Area (Italy) was explored. Quantitative analyses of videoframes obtained from Remote Operated Vehicle records in three different MPA sites, Is Piscadeddus, Santa Caterina, and Serpentara, allow for estimates of both the cover of rhodoliths (considering the main morphotypes) and of C. cylindracea, as well as their competition. All sites showed a well-developed rhodolith bed, although some differences were highlighted in their composition in terms of morphotype, shape, and dimension of rhodoliths, as well as in the C. cylindracea cover. In particular, Santa Caterina appeared to be the site with the highest mean total cover of rhodoliths (68%), and of C. cylindracea (25%). The obtained results suggest that different competitive interactions occur between C. cylindracea and rhodolith beds, in relation to the morphostructural composition of the latter and in response to environmental conditions that affect rhodolith bed composition.

An important gap in the literature on global value chains (GVCs) and bottom-of-the-pyramid markets concerns how GVCs develop to serve frontier markets and what role multinational and local firms play in that process. This paper takes a first step in filling this gap by studying the evolution of Africa's mobile telecommunications industry. Applying a historical analysis, we find that the emergence of GVCs for African frontier markets followed a three-step process: initially, multinational corporations (MNCs) linked host countries to the MNCs' existing value chains; subsequently, local MNC spin-offs experimented in altering key downstream value chains to mitigate the frontier markets' demand- and supply-side challenges, and replicated those value chains in multiple African countries; and finally, other incumbents reoriented their downstream value chains for frontier markets, aided by the development of experienced local labor markets and specialized contractors. A key implication of our findings is the need for sufficient competitive incentives and industry knowledge to stimulate firms to invest in transforming existing GVCs for frontier markets. This process is highly uncertain; however, successful GVC transformation can lead firms to expand in multiple frontier markets, thereby propelling a growth phase across an entire developing region. [ABSTRACT FROM AUTHOR]

Competition is assumed to shape niche widths, affecting species survival and coexistence. Expectedly, high interspecific competition will reduce population niche widths, whereas high intraspecific competition will do the opposite. Here we test in situ how intra‐ and interspecific competition affects trophic resource use and the individual and population niche widths of two lacustrine fish species, Arctic charr and brown trout, covering a 40 year study period with highly contrasting competitive impacts prior to and following a large‐scale fish culling experiment. Initially, an overcrowded Arctic charr population dominated the study system, with brown trout being nearly absent. The culling experiment reduced the littoral Arctic charr density by 80%, whereupon brown trout gradually increased its density in the system. Thus, over the study period, the Arctic charr population went from high to low intraspecific competition, followed by increasing interspecific competition with brown trout. As hypothesized, the relaxed intraspecific competition following the experimental culling reduced individual diet specialization and compressed population niche width of Arctic charr. During the initial increase of the brown trout population, there was a large dietary overlap between the two species. Over the subsequent intensified interspecific competition from the population build‐up of brown trout, their trophic niche overlap chiefly declined due to a dietary shift of Arctic charr towards enhanced zooplankton consumption. Contrary to theoretical expectations, the individual and population niche widths of Arctic charr increased with intensified interspecific competition. In contrast, the diet and niche width of brown trout remained stable over time, confirming its competitive superiority. The large‐scale culling experiment and associated long‐term research revealed pronounced temporal dynamics in trophic niche and resource use of the inferior competitor, substantiating that intra‐ and interspecific competition have large and contrasting impacts on individual and population niches. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) is negatively affecting calcification in a wide variety of marine organisms. These effects are acute for many tropical scleractinian corals under short-term experimental conditions, but it is unclear how these effects interact with ecological processes, such as competition for space, to impact coral communities over multiple years. This study sought to test the use of individual-based models (IBMs) as a tool to scale up the effects of OA recorded in short-term studies to community-scale impacts, combining data from field surveys and mesocosm experiments to parameterize an IBM of coral community recovery on the fore reef of Moorea, French Polynesia. Focusing on the dominant coral genera from the fore reef, Pocillopora, Acropora, Montipora and Porites, model efficacy first was evaluated through the comparison of simulated and empirical dynamics from 2010–2016, when the reef was recovering from sequential acute disturbances (a crown-of-thorns seastar outbreak followed by a cyclone) that reduced coral cover to ~0% by 2010. The model then was used to evaluate how the effects of OA (1,100–1,200 µatm pCO2) on coral growth and competition among corals affected recovery rates (as assessed by changes in % cover y−1) of each coral population between 2010–2016. The model indicated that recovery rates for the fore reef community was halved by OA over 7 years, with cover increasing at 11% y−1 under ambient conditions and 4.8% y−1 under OA conditions. However, when OA was implemented to affect coral growth and not competition among corals, coral community recovery increased to 7.2% y−1, highlighting mechanisms other than growth suppression (i.e., competition), through which OA can impact recovery. Our study reveals the potential for IBMs to assess the impacts of OA on coral communities at temporal and spatial scales beyond the capabilities of experimental studies, but this potential will not be realized unless empirical analyses address a wider variety of response variables representing ecological, physiological and functional domains.

Many applications of immunoassays involve the possible presence of structurally similar compounds that bind with antibodies, but with different affinities. In this regard, an important characteristic of an immunoassay is its cross-reactivity: the possibility of detecting various compounds in comparison with a certain standard. Based on cross-reactivity, analytical systems are assessed as either high-selective (responding strictly to a specific compound) or low-selective (responding to a number of similar compounds). The present study demonstrates that cross-reactivity is not an intrinsic characteristic of antibodies but can vary for different formats of competitive immunoassays using the same antibodies. Assays with sensitive detection of markers and, accordingly, implementation at low concentrations of antibodies and modified (competing) antigens are characterized by lower cross-reactivities and are, thus, more specific than assays requiring high concentrations of markers and interacting reagents. This effect was confirmed by both mathematical modeling and experimental comparison of an enzyme immunoassay and a fluorescence polarization immunoassay of sulfonamides and fluoroquinolones. Thus, shifting to lower concentrations of reagents decreases cross-reactivities by up to five-fold. Moreover, the cross-reactivities are changed even in the same assay format by varying the ratio of immunoreactants' concentrations and shifting from the kinetic or equilibrium mode of the antigen-antibody reaction. The described patterns demonstrate the possibility of modulating immunodetection selectivity without searching for new binding reactants. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) is negatively affecting calcification in a wide variety of marine organisms. These effects are acute for many tropical scleractinian corals under short-term experimental conditions, but it is unclear how these effects interact with ecological processes, such as competition for space, to impact coral communities over multiple years. This study sought to test the use of individual-based models (IBMs) as a tool to scale up the effects of OA recorded in short-term studies to community-scale impacts, combining data from field surveys and mesocosm experiments to parameterize an IBM of coral community recovery on the fore reef of Moorea, French Polynesia. Focusing on the dominant coral genera from the fore reef, Pocillopora, Acropora, Montipora and Porites, model efficacy first was evaluated through the comparison of simulated and empirical dynamics from 2010–2016, when the reef was recovering from sequential acute disturbances (a crown-of-thorns seastar outbreak followed by a cyclone) that reduced coral cover to ~0% by 2010. The model then was used to evaluate how the effects of OA (1,100–1,200 μatm pCO2) on coral growth and competition among corals affected recovery rates (as assessed by changes in % cover y−1) of each coral population between 2010–2016. The model indicated that recovery rates for the fore reef community was halved by OA over 7 years, with cover increasing at 11% y−1 under ambient conditions and 4.8% y−1 under OA conditions. However, when OA was implemented to affect coral growth and not competition among corals, coral community recovery increased to 7.2% y−1, highlighting mechanisms other than growth suppression (i.e., competition), through which OA can impact recovery. Our study reveals the potential for IBMs to assess the impacts of OA on coral communities at temporal and spatial scales beyond the capabilities of experimental studies, but this potential will not be realized unless empirical analyses address a wider variety of response variables representing ecological, physiological and functional domains. [ABSTRACT FROM AUTHOR]

Interactions among wood-decay fungi can have a profound effect on fungal community composition, decay rates and ultimately the chemical composition of the material remaining after the decay process. Interspecific interactions among fungi as they decay wood have been well-studied but almost nothing is known about the effect of intraspecific interactions between individual genets on the decay process. In this study we examine the effect of both intra- and interspecific competition on wood mass-loss for five species of wood-decay fungi: Cerrena unicolor , Fuscoporia gilva , Irpex lacteus , Stereum ostrea and Trametes versicolor. Four of the five species studied showed a significant increase in mass loss when five individual isolates (genets) of the same species simultaneously colonized aspen test wafers in vitro. The dynamics of interspecific interactions were also significantly impacted by the presence of multiple genets of each species. Taken together, these results demonstrate that intraspecific interactions can change the outcome of interspecific interactions and thus the functioning of the overall community. [ABSTRACT FROM AUTHOR]

Traits have been used extensively to predict and understand performance in response to the abiotic environment, but their role for understanding competitive interactions is less understood, especially in nonplant systems. In this study, we evaluate how traits interact with intraspecific density to modulate performance (per capita birth rate) and whether the traits associated with intraspecific competitive ability are similar across multiple species. We used an experimental system of four cladoceran zooplankton species, experimentally manipulated the density of conspecifics, and measured a range of morphological and life history characteristics (body mass, body length, second antenna length, eye diameter, relative growth rate, age at first reproduction, and birth rate). With causal modeling, we identified significant trait–density relationships for three out of four species, although the specific traits that predicted birth rate varied from species to species. In general, individuals at higher densities displayed smaller morphological traits and shifts towards slower relative growth rates and delayed onset of reproduction. We also asked more generally if there are consistent trait‐mediated impacts of density across multiple species. The interspecific model identified significant trait–density relationships for body length, age at first reproduction, and relative growth rate. Unexpectedly, we found little evidence for trait‐based competition due to mechanisms such as limiting similarity or hierarchical competition, and rather noted the potential for trait plasticity and constraints on plasticity affecting performance in response to the competitive environment. [ABSTRACT FROM AUTHOR]

Despite potential negative interactions between biological control agents, the release of multiple agents against invasive alien weeds is often justified. The leaf-feeding beetle Mada polluta Mulsant (Coleoptera: Coccinellidae), released against Tecoma stans (L.) Juss ex Kunth var. stans in South Africa, has so far been unable to contain the weed. Consequently, the root-feeding flea beetle Heikertingerella sp. (Coleoptera: Galerucinae) was introduced to complement M. polluta. The effects of the interaction between the two beetles on their performance and on the target weed were studied on potted T. stans plants in a quarantine glasshouse to assess whether they were additive, synergistic or negative. There was no significant difference in the percentage survival of the P1 adults of either beetle when tested alone or in combination. Mada polluta produced significantly more F1 adult progeny than Heikertingerella sp. when tested alone, while both beetles produced significantly fewer offspring when tested in combination. Leaf damage by M. polluta alone was higher than that caused by Heikertingerella sp. alone, but in combination was not significantly higher than damage by M. polluta alone. Although both beetles on their own caused a significant reduction in leaf density relative to the control, leaf density was significantly lower when in combination. Despite significant reductions in plant height relative to the control, the differences between the three beetle treatments were not significant. Although competitive interactions caused a trade-off between agent proliferation and their impact on the growth of T. stans, these data need to be confirmed in the field. [ABSTRACT FROM AUTHOR]

Immobilization of mercury (Hg) leaching from bank soils of East Fork Poplar Creek (EFPC) is considered part of remediation strategies to mitigate the amount of Hg entering the creek. Different approaches are currently being evaluated, such as utilizing engineered sorbents to immobilize Hg species in EFPC bank soils. However, the influence of environmental microbes on the immobilization of Hg by sorbents is unknown. Organocation-modified phyllosilicate clay minerals (organoclays) are widely used as sorbents for the immobilization of contaminants. This study evaluates the interactions of Serratia marcescens and Burkholderia thailandensis with the sorbent Organoclay PM-199 and their impact on the immobilization of Hg under aerobic conditions. We evaluated the competitive binding of Hg between sorbents and selected microorganisms in a series of pure culture studies using bacterial strains identified in EFPC bank soil samples. Our results suggest that Hg sorption by Organoclay PM-199 is not significantly impacted by common soil bacteria present in EFPC, specifically Serratia marcescens and Burkholderia thailandensis, which are known to form biofilms. These findings suggest that sorbent amendments are an effective strategy for the remediation of Hg contamination in natural ecosystems. [ABSTRACT FROM AUTHOR]

The non-native, aggressive, convict cichlid Amatitlania nigrofasciata is often regarded as a cause for the decline of native Mexican mojarra Cichlasoma istlanum in Mexican rivers. Convict cichlids are assumed dominant in areas they invade. Cooperative territorial defense has been observed in convict cichlids, suggesting that they can dominate Mexican mojarras by coalition. Behavioral observations were recorded and analyzed to experimentally test hierarchical dominance establishment (ES) and maintenance (MN) between uneven numbers of both species. Counts of aggressive interactions (bites, chases, and confrontations) between species were used to measure dominance in ES and MN interactions. More chases and bites were made by Mexican mojarra than convict cichlids in both ES and MN tests. Mexican mojarra attained and maintained dominance against two convict cichlids when competing for food resources via increased antagonistic interactions. Intraspecific confrontations were more common than interspecific confrontations for convict cichlids. Our results offer insight into competition mechanisms potentially occurring in natural settings, suggesting that while convict cichlids may be exploitative and interference competitors to Mexican mojarra, behavioral interactions between these species may not be the sole cause of observed Mexican mojarra population declines in freshwater ecosystems throughout western and southern Mexico. Significance statement: Successfully established non-native freshwater fishes are often regarded as better competitors than native fishes. Populations of the native fish Mexican mojarra, Cichlasoma istlanum, have been hypothesized to be negatively affected by the introduction of the non-native convict cichlid, Amatitlania nigrofasciata. Behavioral observations were analyzed to demonstrate that a native fish can outcompete and establish and maintain hierarchical dominance over non-native fish, even when at numerical disadvantage. We expected to find a cooperative territorial defense strategy as a mechanism to obtain dominance and hypothesized that hierarchies among these species would be determined by the number of individuals of each species present in contests. Mexican mojarra consistently attained and maintained dominance over convict cichlids via increased antagonistic interactions despite being outnumbered. Our results suggest that behavioral interactions between these species may not be the sole cause of observed Mexican mojarra population declines. [ABSTRACT FROM AUTHOR]

Competitive interactions between corals and macroalgae play an important role in determining benthic community structure on coral reefs. While it is known that macroalgae may negatively affect corals, the relative influence of contact- versus water-mediated macroalgal interactions on corals – such as via an influence on coral-associated microbiomes – is less well understood. Further, the impacts of macroalgae on corals that have persisted in a heavily urbanized reef system have not been explored previously. We examined the effects of the macroalgae Lobophora sp. and Hypnea pannosa on the physiology and microbiome of three Indo-Pacific coral species (Merulina ampliata, Montipora stellata, and Pocillopora acuta) collected from two reefs in Singapore (Pulau Satumu and Kusu Island), and compared how these effects varied between direct contact and water-mediated interactions. Direct contact by Lobophora sp. caused visible tissue bleaching and reduced maximum quantum yield (Fv/Fm) in all three coral species, while direct contact by H. pannosa only led to slight, but significant, suppression of Fv/Fm. No detrimental effects on coral physiology were observed when corals were in close proximity to the macroalgae or when in direct contact with algal mimics. However, both direct contact and water-mediated interactions with Lobophora sp. and H. pannosa altered the prokaryotic community structures in M. stellata. For M. ampliata and P. acuta, the changes in their microbiomes in response to algal treatments were more strongly influenced by the source reefs from which the coral colonies were collected. In particular, coral colonies collected from Kusu Island had proportionately more initial abundances of potentially pathogenic bacteria in their microbiomes than those collected from Pulau Satumu; nevertheless, coral fragments from Kusu Island had the same physiological responses to macroalgal interactions as corals from Pulau Satumu. Overall, our results reveal that, for the species tested, the coral microbiomes were sensitive to both direct contact and water-mediated interactions with macroalgae, while coral physiology was only compromised when in direct contact. Further, the presence of high levels of potentially pathogenic bacteria in some of the coral samples did not lead to the corals being more susceptible to impacts from macroalgae.

Competitive interactions not only exist between invasive and native fish species but also between different invasive species, especially between those that have broad niche overlap. Nile tilapia (Oreochromis niloticus) and Redbelly tilapia (Tilapia zillii) are the most common invasive tilapia species in the rivers of South China. There may be specific factors that influence their competitive interactions and disturbance patterns, and temperature has been considered the most important factor. To study how temperature affects the distribution patterns and competitive interactions of these two invasive tilapia species, field surveys and laboratory experiments were conducted. Field surveys showed that latitude affected the ratio but not the biomass of all tilapia species. Nile tilapia was more abundant in the southern (warmer) sites, and Redbelly tilapia was more abundant in the northern (colder) sites. The distribution patterns of the two tilapia species were also related to latitude and minimum winter temperature. The results of the laboratory-based temperature experiments further confirmed that Redbelly tilapia can tolerate lower temperatures than Nile tilapia. However, the Nile tilapia were larger in field surveys, and laboratory experiments also showed that Nile tilapia are stronger competitors in warmer water because of their larger body size. Therefore, we suggest that the distribution patterns of these two invasive tilapia species were related to temperature conditions.

Aim: The links between taxonomic, functional, and phylogenetic diversity and how these vary geographically are key to understanding how historical and contemporary processes have shaped communities at regional and local scales. Here, we evaluate the links between taxonomic, functional and phylogenetic diversity for the amphibians in the Continental Americas and how these vary geographically under an explicit hypothesis testing framework. Location: Continental Americas. Taxon: Amphibia. Methods: We identify spatial disparities between biodiversity dimensions (taxonomic, functional and phylogenetic) using geographically weighted regressions. Based on these mismatches we examined whether different eco‐evolutionary processes would fit (competitive exclusion, habitat filtering, available ecological space, strong biotic interactions, speciation rates, and dispersion). Results: We found extensive variation in spatial mismatches between the three dimensions of biodiversity examined here. In general, at higher latitudes, we detected relatively little phylogenetic diversity, suggesting rapid functional diversification from temperate clades. In contrast, at low latitudes, environmental filtering mechanisms appear to be restricting functional diversity. Main conclusions: The geographical mismatches between dimensions of diversity suggest different eco‐evolutionary causes. Patterns of diversification across amphibian lineages demonstrate how different environments can have contrasting effects on the different dimensions of diversity, potentially leading to decoupling. Neither dimension of alpha diversity of amphibians is a general predictor for another, and thus, general explanations for amphibian diversity and evolution should be avoided. Nonetheless, these dimensions can provide critical insights about conservation measures that explicitly emphasize evolutionary history, functionality or classic species richness. [ABSTRACT FROM AUTHOR]

It has been demonstrated that Ipomoea batatas (L.) Lam (sweet potato) has greater soil nutrient absorption ability when grown in association with the invasive plant Mikania micrantha Kunth (mile-a-minute), but the competition interaction of the two plant species under different fertilization levels is not well characterized. The current study utilized a de Wit replacement series incorporating three ratios of I. batatas and M. micrantha densities and four different fertilizer levels in 16 m² plots. In mixed culture, the total shoot length, branch, leaf, and biomass of M. micrantha were significantly suppressed (P < 0.05) by I. batatas. With increasing fertilization, total shoot length, branch, leaf, and biomass of I. batatas and M. micrantha were significantly increased, but at a greater rate for I. batatas than for M. micrantha. Relative yield parameters demonstrated that intraspecific competition was less than interspecific competition and that I. batatas had a higher competitive ability than M. micrantha under different fertilization levels. Fertilization significantly impacted the photosynthetic rate (Pn) of these species in June and July, whereas density ratio had greater effect on Pn of both species in August and September. Growth rates of I. batatas were markedly higher than those of M. micrantha in July and August, but less than those of M. micrantha in June and September. The concentrations of soil organic matter, and available N, P, and K in M. micrantha infested soil were significantly greater (P < 0.05) than soils where I. batatas was grown in monoculture, and fertilization levels were reduced by the presence of I. batatas in mixed culture. With increased fertilization, soil nutrient absorption increased, at a greater rate for I. batatas than for M. micrantha. Our results demonstrated that I. batatas could gain greater competitive advantage from enriched fertilization levels than M. micrantha. If I. batatas is incorporated into cropping system rotations, optimal fertilizer levels could be designed using information from our study to produce high I. batatas yields in addition to the benefits of suppressing invasive plants like M. micrantha. [ABSTRACT FROM AUTHOR]

Declines or mid‐elevation peaks in invertebrate diversity with elevation are often attributed to climate and geometric constraints. However, vegetation structure may also drive diversity patterns, especially for tree‐dwelling species, via its effects on microhabitat use and competitive interactions. Here we investigate these effects on the diversity and community structure of tree‐nesting ants over elevation. We exhaustively sampled ant nests in 1254 trees within continuous plots of primary rainforest at low (200 m a.s.l.), mid (900 m a.s.l.) and high (1800 m a.s.l.) elevation in Papua New Guinea. Ant diversity, nest abundance and tree occupancy peaked at mid‐elevation. Although host tree diversity also peaked at mid‐elevation, there was low specialisation of ant species to tree species at all elevations. Mid‐elevation trees hosted more species, more nests and a greater diversity of nest types than trees of a similar size at low or high elevation. Tree size and nest microhabitat use were the strongest predictors of species composition, explaining twice as much of the variability in the communities than elevation. At mid to high elevation there were proportionally fewer large nests than in the lowlands, with an increase in smaller nests in live hollow twigs and epiphytes. There was high species turnover between elevations, and between trees within elevations. Species co‐occurrence patterns within trees differed with tree size, and with elevation. In large trees species tended to co‐occur at random at low and high elevation, but co‐occurred more often than expected by chance at mid elevation, indicating an elevational shift in competitive interactions. We conclude that the more extreme diurnal temperatures at higher elevations, combined with increased epiphyte availability, drive ants to nest in more insulated microhabitats. This results in smaller colony sizes and a decrease in interspecific competition, thereby boosting species co‐existence at mid elevation. [ABSTRACT FROM AUTHOR]

Many applications of immunoassays involve the possible presence of structurally similar compounds that bind with antibodies, but with different affinities. In this regard, an important characteristic of an immunoassay is its cross-reactivity: the possibility of detecting various compounds in comparison with a certain standard. Based on cross-reactivity, analytical systems are assessed as either high-selective (responding strictly to a specific compound) or low-selective (responding to a number of similar compounds). The present study demonstrates that cross-reactivity is not an intrinsic characteristic of antibodies but can vary for different formats of competitive immunoassays using the same antibodies. Assays with sensitive detection of markers and, accordingly, implementation at low concentrations of antibodies and modified (competing) antigens are characterized by lower cross-reactivities and are, thus, more specific than assays requiring high concentrations of markers and interacting reagents. This effect was confirmed by both mathematical modeling and experimental comparison of an enzyme immunoassay and a fluorescence polarization immunoassay of sulfonamides and fluoroquinolones. Thus, shifting to lower concentrations of reagents decreases cross-reactivities by up to five-fold. Moreover, the cross-reactivities are changed even in the same assay format by varying the ratio of immunoreactants’ concentrations and shifting from the kinetic or equilibrium mode of the antigen-antibody reaction. The described patterns demonstrate the possibility of modulating immunodetection selectivity without searching for new binding reactants.

In savannas, grazing is an important disturbance that modifies the grass layer structure and composition. Habitat structural complexity influences species diversity and assemblage functioning. By using a combination of natural sites and manipulated experiments, we explored how habitat structure (grazing lawns and adjacent bunch grass) affects ant diversity and foraging behaviour, specifically the efficiency of resource acquisition, resource monopolisation and ant body size. We found that in the natural sites there was no difference in the amount of time ants took to locate resources, but in the manipulated experiments, ants were faster at locating resources and were more abundant in the simple treatments than in the more complex treatments. Ant body size was only affected by the manipulated experiments, with smaller ants found in the more complex treatments. In both the grazing lawn and bunch grass habitats there were differences in assemblage patterns of ants discovering resources and those dominating them. Seasonality, which was predicted to affect the speed at which ants discovered resources and the intensity of resource monopolisation, also played a role. We show that ants in winter monopolised more baits and discovered resources at a slower rate, but only at certain times within the experiment. Grazing in conjunction with season thus had a significant effect on ant diversity and foraging behaviour, with dominant ants promoted where habitat complexity was simplified when temperatures were low. Our results indicate that structural complexity plays a major role in determining ant assemblage structure and function in African savannas.

Investigating how climate change alters selection regimes is a crucial step toward understanding the potential of populations to evolve in the face of changing conditions. Previous studies have mainly focused on understanding how changing climate directly influences selection, while the role of species' interactions has received little attention. Here, we used a transplant experiment along an elevation gradient to estimate how climate warming and competitive interactions lead to shifts in directional phenotypic selection on morphology and phenology of four alpine plants. We found that warming generally imposed novel selection, with the largest shifts in regimes acting on specific leaf area and flowering time across species. Competitors instead weakened the selection acting on traits that was imposed directly by warming. Weakened or absent selection in the presence of competitors was largely associated with the suppression of absolute means and variation of fitness. Our results suggest that although climate change can impose strong selection, competitive interactions within communities might act to limit selection and thereby stymie evolutionary responses in alpine plants facing climate change., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Society for the Study of Evolution (SSE) and European Society for Evolutionary Biology (ESEN).)

Resource availability may modulate interference interactions among competitors. For example, competition among stream fishes for drifting eggs from salmon (Oncorhynchus spp.) spawning events may be influenced by the availability of this energy-rich food source. This study used camera-based techniques to evaluate the effect of varied prey availability (i.e., pink salmon (O. gorbuscha) eggs) on rates of interference competition within natural stream fish communities at 10 sites. Aggressive interactions were quantified across different levels of egg additions, ranging from 6 to 3575 O. gorbuscha eggs, at 10 sites on the Keogh River, British Columbia, Canada. There were fewer aggressive interactions among salmonids (O. kisutch, O. mykiss, and O. clarkii clarkii) when there were more available eggs. Aggressive interaction rates were species-dependent; for example, the number of aggressive acts relative to null expectations based on abundances were highest in juvenile coho (O. kisutch) towards conspecifics. For some interactions, size of fish appeared to be a key factor as well. Thus, higher densities of spawning salmon in streams may provide sufficient prey resources in the form of eggs to temporarily decrease interference competition among stream fishes. [ABSTRACT FROM AUTHOR]

Understanding species coexistence has long been a major goal of ecology. Coexistence theory for two competing species posits that intraspecific density dependence should be stronger than interspecific density dependence. Great tits and blue tits are two bird species that compete for food resources and nesting cavities. On the basis of long‐term monitoring of these two competing species at sites across Europe, combining observational and manipulative approaches, we show that the strength of density regulation is similar for both species, and that individuals have contrasting abilities to compete depending on their age. For great tits, density regulation is driven mainly by intraspecific competition. In contrast, for blue tits, interspecific competition contributes as much as intraspecific competition, consistent with asymmetric competition between the two species. In addition, including age‐specific effects of intra‐ and interspecific competition in density‐dependence models improves predictions of fluctuations in population size by up to three times. [ABSTRACT FROM AUTHOR]

In 2017, Norway experienced an invasion of the Pacific salmonid pink salmon (Oncorhynchus gorbuscha) in numbers never before seen in rivers all along the coast. Significant numbers were also caught in other parts of northwestern Europe. Pink salmon has been observed in variable numbers in Norwegian waters in the summer and autumn of most years since 1960, after the first successful Russian introduction of pink salmon fry in rivers draining to the White Sea in northwest Russia in 1959. With the exception of 1960, pink salmon have been most abundant in odd years, based on the odd-year broodline of the 2-year life salmonid. Even-year fish has generally been less abundant, but in recent years, significant numbers of this broodline have also been caught. In this paper we review the available information on pink salmon in Norwegian rivers and discuss (1) to what extent the presence of this species in Norway has been driven by Russian introductions and natural reproduction in Russian, and lately in Norwegian, rivers, and (2) the likelihood of reproducing populations of pink salmon being established in more Norwegian rivers. Considering the continued propagule pressure in terms of adult pink salmon entering and spawning in Norwegian rivers, it is puzzling that self-propagating populations apparently only have been established in some rivers in the northernmost part of the country. The potential impact of pink salmon on native salmonids and river ecosystems is discussed briefly. Extensive research is required to understand the mechanisms that determine the fate of pink salmon as an alien species, and specifically the possible impact of pink salmon on native salmonids and the environment in the recipient rivers and in the ocean. [ABSTRACT FROM AUTHOR]

In savannas, grazing is an important disturbance that modifies the grass layer structure and composition. Habitat structural complexity influences species diversity and assemblage functioning. By using a combination of natural sites and manipulated experiments, we explored how habitat structure (grazing lawns and adjacent bunch grass) affects ant diversity and foraging behaviour, specifically the efficiency of resource acquisition, resource monopolisation and ant body size. We found that in the natural sites there was no difference in the amount of time ants took to locate resources, but in the manipulated experiments, ants were faster at locating resources and were more abundant in the simple treatments than in the more complex treatments. Ant body size was only affected by the manipulated experiments, with smaller ants found in the more complex treatments. In both the grazing lawn and bunch grass habitats there were differences in assemblage patterns of ants discovering resources and those dominating them. Seasonality, which was predicted to affect the speed at which ants discovered resources and the intensity of resource monopolisation, also played a role. We show that ants in winter monopolised more baits and discovered resources at a slower rate, but only at certain times within the experiment. Grazing in conjunction with season thus had a significant effect on ant diversity and foraging behaviour, with dominant ants promoted where habitat complexity was simplified when temperatures were low. Our results indicate that structural complexity plays a major role in determining ant assemblage structure and function in African savannas. [ABSTRACT FROM AUTHOR]