Modulating biodiversity through higher-order interactions and intraspecific competition in rock–paper–scissors dynamics

Interactions between pests and their natural enemies play a central role in ecological balance and sustainable pest management. In the present work, we examine a prey-predator system in which the predator population experiences intra-specific competition and receives an external food supplement. The feeding mechanism of the predator follows a Holling type-III functional response. We demonstrate that the proposed formulation admits a unique, globally positive solution and investigate the stability of its equilibria. Analytical exploration reveals the occurrence of distinct bifurcation phenomena, including transcritical and saddle-node transitions. Numerical investigations further illustrate the emergence of hysteresis loops, indicating bistability within specific parameter ranges. Experimental observations concerning the predation of Bemisia tabaci by Orius albidipennis validate the Holling type-III assumption and serve to parameterize the theoretical model. The findings underscore the dual impact of additional food and predator competition in shaping biological control outcomes and improving pest suppression efficiency.

Global dynamics of an intraguild predation predator-prey model with density-dependent velocity suppression.

The commercial use of chitin synthesis inhibitor (CSI) bait formulations is common against many subterranean termite pest species, but is seldom used against termitid pests. In this study, noviflumuron durable baits were implemented under an experimental protocol in a tropical garden (Sir Seewoosagur Ramgoolam Botanical Garden [SSRBG]) on the island country of Mauritius to test their field efficacy against a pest population of Nasutitermes mauritianus (Wasmann) (Blattodea, Termitidae, Nasutitermitinae) (=syn. N. voelzkowi). With 46 treated nests and 26 control nests within the garden, 40 treated nests lost termite activity within 5 months, and all 46 treated nests were inactive at 8 months after treatment. In addition, 14 out of 26 control nests also ceased activity, implying that polydomous colonies were eliminated over distance even if just one of their multiple nests was treated with noviflumuron. Within 8 months, 83% of all nests in the garden were inactive. As bait quantity was limited in this experimental protocol, the garden was then left untreated for 3 years to observe the reestablishment of new colonies, through foundation, emergence of concealed colonies, and expansion of mature colonies over time, revealing a potential intraspecific competition dynamic among colonies during colony reestablishment process. Ultimately, CSI baits can be used against Nasutitermes colonies, which suggests that area-wide management of Nasutitermes is possible if colonies can be readily baited upon discovery through routine inspections, especially in areas with high termite pressure, such as the one reported in the SSRBG.

Aedes aegypti is the primary vector of dengue virus (DENV), a major arboviral disease affecting human health. Variation in detritus inputs and larval competition in containers where the species develop can influence female Ae.aegypti phenotypic traits, nutrient content (carbon, nitrogen, C:N ratio), and elemental isotopes (δ13C and δ15N), ultimately affecting vector competence for DENV. Female Ae.aegypti were reared under simulated urban detritus levels (low, medium, and high) and larval intra- (30:0 and 60:0) and interspecific (30:30 and 60:60) competition with Ae.mediovittatus (Ae.aegypti: Ae.mediovittatus). Aedes aegypti were offered a DENV-1-infected bloodmeal. Transmission assays were conducted, followed by assessment of susceptibility to infection, disseminated infection, and transmission rates. Body nutrient composition and isotope values were measured and analyzed in relation to phenotypic traits and vector competence for DENV-1, with male body nutrient profiles used as proxies for females where sample sizes were limited. Longer development time and reduced wing length in Ae.aegypti were associated with low detritus. Wing length increased under interspecific competition with Ae.mediovittatus but decreased under intraspecific competition. Higher δ15N values in Ae.aegypti body tissues were associated with greater detritus availability and with interspecific competition. DENV-1 dissemination exhibited a nonlinear relationship with δ15N, showing high dissemination at low δ15N, the lowest dissemination at intermediate δ15N, and an increase at higher δ15N. Vector competence for DENV-1 was reduced under conditions of low detritus and low intraspecific competition (30:0). High interspecific competition combined with high detritus negatively affected Ae.aegypti phenotypic traits and reduced DENV-1 vector competence. Under the most extreme conditions (high interspecific competition, 60:60, and high detritus), Ae.aegypti failed to reach adulthood. At intermediate detritus levels for the same density, Ae.aegypti exhibited high rates of DENV-1 disseminated infection. This research underscores the importance of larval crowding and nutritional availability experienced during the immature stages of Ae.aegypti on adult nutrient stoichiometry and DENV-1 infection. These findings suggest the potential use of δ15N as a tool to assess how larval nutritional and competitive environments shape dengue vector competence, with implications for understanding and predicting Ae.aegypti-driven DENV-1 dynamics in urban and suburban areas. Interpretations should consider that female nutrient estimates were partially inferred from male data due to low female sample sizes, survivorship was estimated assuming a 1:1 sex ratio, and some high-mortality treatments lacked surviving adults.

Microplastics reduce population viability without shifting clonal structure in Daphnia pulex.

Prior research has demonstrated that the natural regeneration of Korean pine ( Pinus koraiensis ) in old-growth forests is quantitatively constrained by the composition of parent trees. To further explore the spatial relationships between regenerated and maternal Korean pine, we examined the spatial patterns of its regeneration across four ontogenetic stages (younger seedlings, older seedlings, smaller saplings, and taller saplings) in five old-growth mixed forest stands representing a gradient of Korean pine basal area proportion (33%-77%). Using spatial point pattern analysis with crown-projected coordinates, we quantified intra- and interspecific spatial associations. Results revealed that Korean pine natural regeneration is forest-type-specific, with the ribbed birch ( Betula costata )-Korean pine forest being the most conducive to regeneration. Distribution patterns indicated a density-dependent ontogenetic shift: regenerated individuals exhibited strong aggregation at the early stage, which shifted to a random-dominated distribution in later stages, a trend amplified in stands with higher proportions of Korean pine. Associations between younger seedlings and parent trees transitioned from fine-scale facilitation to broad-scale repulsion ( p < 0.05), but only where the Korean pine proportion was approximately 50%. Notably, most heterospecific associations were neutral, with facilitation being highly species- and context-specific. We conclude that high conspecific occupancy intensifies intraspecific competition, whereas neutral associations with broadleaved species suggest that niche partitioning governs coexistence. Conservation strategies should therefore focus on regulating parent tree density and maintaining stand diversity to ensure sustainable regeneration. Methodologically, we recommend that future point pattern analyses of large canopy trees, particularly those with severe crown asymmetry, using crown coordinates.

Injuries are common in animals and represent a major threat to individual survival. They can result from inter- or intraspecific conflict, predation, or pugnacious prey. Despite their potential ecological and evolutionary importance, injury patterns remain poorly documented in animal populations. To test whether a species’ feeding ecology or habitat can predict injury patterns, we quantified injury rates and affected body regions among native ant species collected from different habitats in Bavaria, Germany. Specimens were sampled using pitfall traps, which proved to be an efficient method for injury assessment. Injury rates varied substantially among species and genera, ranging from 0% to 38%. Predatory ant species exhibited higher frequencies of leg injuries, whereas omnivorous species were more frequently injured at the antennae. The distribution of injuries likely reflects both foraging ecology and species-specific wound care behaviors, with a high frequency of trochanter injuries potentially indicating prior amputation events to cope with infected leg injuries, as observed in Lasius alienus. Our findings demonstrate that injury propensity and distribution are shaped by feeding habits and behavioral adaptations, providing comparative evidence that the costs and management of injuries vary systematically among ant species. Our study thus highlights injuries as a measurable axis of selection that may have contributed to the emergence of wound care and other forms of social immunity in ants.

Root-mediated conspecific recognition and avoidance could alleviate intraspecific competition and promote interspecific competitive abilities. This could result in communities dominated by few species. However, it remains unclear whether invasive plants, which frequently become dominant, possess higher capabilities of root recognition and segregation than natives. We compared root-recognition and segregation capabilities between five congeneric pairs of invasive and native plants using a split-root assay and an intraspecific root-distribution experiment. We also assessed the roles of soil microbial legacies in root-segregation capabilities. The split-root assay showed that invasive plants exhibited stronger root-recognition capacities than natives by reducing root allocation toward conspecifics. The intraspecific root-distribution experiment showed that both invasives and natives exhibited root segregation when grown on unconditioned soils. However, when grown on soils conditioned by either invasive or native plants, root segregation of natives disappeared, whereas invasives remained unaffected. Changes in root segregation of natives were associated with changes in the composition of soil fungal and bacterial communities. Invasive plants possess mechanisms of avoiding intensive intraspecific competition irrespective of soil microbial legacies, whereas for native plants, these mechanisms can be disrupted by soil microbial legacies. This could contribute to the competitive superiority of invasive plants.

A tree-level inventory dataset of Picea crassifolia forests in the Qilian Mountains for spatial point pattern and neighbor competition analysis

Dispersal in animals is influenced by diverse environmental cues, among which population density and kinship are key drivers. High density can promote dispersal by intensifying intraspecific competition or inhibit it through group-living advantages. Likewise, kin interaction may enhance dispersal via kin competition or limit it through kin-selected fitness gains. However, the interplay between them remains inadequately elucidated. We investigated how density and kinship interacted to influence natal dispersal in silver-throated tits (Aegithalos glaucogularis), a social species showing facultative cooperative breeding during the breeding season and group living thereafter. We found female-biased natal dispersal, consistent with male-biased helping behaviour. For males, the natal dispersal distance was negatively associated with the number of male siblings fledging from the same nest, and this relationship intensified with increasing fledgling density around the natal nest, indicating that density can modulate kin selection's inhibiting effect on dispersal. Furthermore, with increasing male sibling number, fledgling density's effect on male dispersal distance shifted from positive to negative, suggesting that potential kin selection opportunity can reverse the direction of the density effect. These findings demonstrate that density and kin selection opportunities interact to shape dispersal dynamics, offering new insights into their combined roles in driving the evolution of dispersal strategies.

Abstract Habitat selection is a dynamic process influenced by population density, yet few studies have tested the effects of density on habitat selection of large herbivores within enclosed systems. We used long‐term global positioning system (GPS) collar data from 22 adult female plains bison ( Bison bison bison ) in a fenced enclosure in Grasslands National Park, Canada, to test for density‐dependent habitat selection across biologically relevant seasons at 2 spatial scales. The study leveraged a unique opportunity created by a period of natural population growth followed by biennial population reductions to explore how bison adjust habitat use under varying density conditions. Resource selection functions and latent selection difference models showed that bison selected high normalized difference vegetation index (NDVI) areas and avoided roads at low density. As density increased, selection patterns generalized or reversed, especially during the calving and post‐calving seasons when nutritional demands were greatest. Bison consistently avoided roads, suggesting they perceive human activity as a form of risk. However, this avoidance declined during the rut, likely because of changes in herd composition and behavioral priorities. Seasonal variation in the strength and direction of selection highlights the complexity of density‐dependent space use. Our results emphasize that ignoring density in spatial models may lead to biased management decisions. Understanding how space use shifts with population density is especially important for fully fenced populations that cannot disperse naturally and where intraspecific competition is likely to be exacerbated. In such systems, incorporating density‐dependent behavior into species or habitat monitoring is essential for anticipating ecological outcomes and guiding long‐term management.

Context Understanding the biological and environmental processes that regulate populations is a central goal of ecology and is fundamental to fisheries management. Aims This study aims to quantify the environmental and biological factors influencing barramundi (Lates calcarifer) recruitment dynamics in Corroboree Billabong, a seasonally isolated reach of the Mary River, located in the wet–dry tropics of northern Australia. Methods Depletion sampling was conducted annually by using gillnets, and the age of sampled individuals was estimated, providing age-specific abundance estimates across a 20-year period. To explore the biotic (e.g. density dependence) and abiotic (e.g. rainfall) drivers of recruitment and size-at-age, a Piecewise Structural Equation Model was developed. Key results Young-of-year recruitment was negatively correlated with 1-year-old abundance, and size-at-age was negatively correlated with cohort strength, suggesting that cannibalism and intraspecific competition are important determinants of recruitment and juvenile growth rates respectively. Wetter years were associated with stronger recruitment, and higher rates of emigration by 1-year olds. Conclusions Our results provided new insights into river–floodplain fish recruitment dynamics showing that both density-dependent and abiotic drivers can affect recruitment dynamics. Implications Incorporating both abiotic and biotic drivers may improve the predictive capacity of population and stock assessment models to underpin sustainable management of this valuable and iconic species.

ABSTRACTSeasonal environmental fluctuations profoundly influence ectothermic vertebrates, regulating their physiology, metabolism, and life cycles. This study investigated the metabolic and morphometric seasonal dynamics of the subtropical sand lizard Liolaemus arambarensis, an endangered species endemic to the coastal dunes of southern Brazil. Over two annual cycles (July 2020 to May 2022), 133 individuals (43 males, 45 females, 45 juveniles) were sampled across all seasons. Through an ecophysiological and biochemical approach, we quantified intermediate metabolism biomarkers—including glucose, proteins, albumin, uric acid, lactate, triglycerides, cholesterol, glycogen, and total lipids—in plasma, liver, gonads, and skeletal muscles, alongside somatic and organ indices. Data were analyzed using generalized linear models (GLMs) with gamma distribution and log‐link, followed by type III ANOVA and Tukey post hoc tests. Marked sex‐ and age‐specific seasonal patterns were detected. Females exhibited strong reproductive investment in spring and summer, characterized by increased gonadal proteins and triglycerides, elevated plasma albumin and cholesterol, and depletion of hepatic and muscular reserves—consistent with vitellogenesis and egg production. Males initiated reproductive investment earlier, accumulating hepatic and muscular glycogen and lipids in autumn–winter and mobilizing these reserves during spring for spermatogenesis and reproductive behaviors. Juveniles displayed strategies oriented toward somatic growth and survival, with high tissue lipid content in summer (yolk‐derived reserves), hyperglycemia and hepatic glycogen accumulation in winter (suggesting cryoprotective or osmotic roles), and metabolic depletion in autumn, likely due to intraspecific competition for limited resources. The results reveal a plastic physiological strategy combining temperate‐like energy conservation during cold periods with tropical‐like reproductive allocation in warm months. Such metabolic flexibility underlies the species' adaptation to subtropical thermal variability and provides valuable predictive indicators for ecological modeling and conservation planning in the context of ongoing climate change.

Urbanization is reshaping ecosystems worldwide, driving wildlife to navigate and adapt to novel and highly dynamic environments. The Eurasian tree sparrow (Passer montanus, ETS) serves as an exemplary human commensal, thriving in cities through exceptional behavioral and ecological flexibility. Here, we systematically investigated the nest-site selection strategies of ETSs across 645 residential buildings across 22 cities in northern China, integrating climatic, geographic, biotic, and anthropogenic variables at a macroecological scale. We found that both the availability and use of nest height preference increased with building height, underscoring ETSs' capacity to exploit vertical resources in dense urban landscapes. Notably, the preference for lower nest heights when nest sites were abundant suggests a strategy to reduce intraspecific competition and energy expenditure. Negative associations between nest-site use or preference and the normalized difference vegetation index indicate that ETSs favor anthropogenic over vegetated resources, likely to circumvent interspecific competition in urban green spaces. Additionally, altitudinal gradients modulated ETSs' nesting responses: At lower elevations, higher building heights promoted nesting, whereas increased economic development (gross domestic product per cell) and noise suppressed it-signaling an avoidance of intense anthropogenic disturbance. Conversely, ETSs showed reduced competition at higher altitudes and increasingly relied on resources linked to urban prosperity. These findings reveal context-dependent patterns of nest-site selection in ETSs across multidimensional urban gradients. Our study documents behavioral plasticity in a highly successful urban-commensal species and highlights the need for future research linking such patterns to individual fitness, population persistence, and broader biodiversity management in cities.

The islet of Vaixell, off the west coast of Ibiza (Balearic Islands, Spain), is home to a native population of the Pityusic wall lizard, Podarcis pityusensis, with the largest body size recorded for the species. These lizards live in extreme environmental conditions on an islet with a small surface area covered by very sparse vegetation. The sex ratio is balanced, and a very high incidence of missing toes and autotomized tails is observed, indicating strong intraspecific competition involving both males and females. The body growth rate, adjusted using the Gompertz model, is intense and, apparently, juvenile lizards quickly reach relatively large body sizes. This fast body growth is probably a strategy against predation pressure from conspecifics. In P. pityusensis from Vaixell, the peak growth acceleration is prenatal and practically coincides with the moment of hatching. The diet consists mainly of aggregated prey, such as ants, with the inclusion of marine subsidies, such as halophyllous and littoral isopods, and a lower consumption of plant matter compared to other insular populations of lizards from the Balearic Islands. The lizards of Vaixell are an excellent example of the adaptive response of a lacertid lizard to the extreme conditions on the small coastal islets of the Mediterranean, with very small available areas, high population density, but a small population size, of about 50 to 100 lizards, which also reach a remarkable longevity.

Negative plant–soil feedback (NPSF) drives yield decline in monocropping systems, yet how intraspecific competition modulates NPSF across planting densities remains unclear. We conducted a two-stage plant–soil feedback experiment using five crops (Triticum aestivum L., Zea mays L., Solanum lycopersicum L., Cucumis sativus L., and Panax notoginseng (Burkill) F.H. Chen) with contrasting NPSF intensities under four planting densities (30 × 30 to 8 × 8 cm). Crops with stronger NPSF (P. notoginseng) showed pronounced density-dependent biomass reductions, whereas those with moderate (S. lycopersicum, C. sativus) or low (Z. mays, T. aestivum) NPSF were largely density-insensitive. Given its sensitivity, P. notoginseng was used to explore mechanisms. High-density planting (8 × 8 cm) intensified NPSF, reducing seedling survival by 88.54% and biomass by 56.08% compared with low-density controls (30 × 30 cm). Microbiome profiling showed enrichment of pathogenic Fusarium spp. and depletion of beneficial Humicola spp. under high density. Metabolomic analysis identified linoleic acid and oleamide as key root exudates upregulated under high-density stress, which selectively stimulated Fusarium growth as preferred carbon sources. Collectively, these results reveal a density-dependent feedback in which intensified competition reshapes root exudation, promotes pathogen proliferation, and suppresses beneficial taxa, thereby amplifying NPSF. This provides mechanistic insights into microbially mediated NPSF under density stress and highlights the importance of optimizing planting density to sustain crop productivity.

Gut microbial community composition varies from one person to another. Potentially, this means the ecological interactions experienced by individual strains or species also vary among microbiomes of different people. However, testing this directly in human microbiomes and identifying ecological drivers involved are challenging. Here, we use replicated anaerobic microcosms to quantify variability of population growth for a key commensal species among microbiome samples from different individuals and to identify underlying intra- and interspecific interactions. In a reciprocal transplant experiment, both absolute and relative growth performance of different Escherichia coli strains varied among gut microbiome samples from healthy individuals. This was partly explained by intraspecific competition: growth performance of individual E. coli strains was associated with displacement of resident conspecifics. However, the determinants of E. coli growth varied among samples. In one microbiome sample with a distinctive taxonomic composition, culture acidification by resident microbes impaired growth of all E. coli strains. We identified a strain of Clostridium butyricum contributing to this effect and showed that transferring it into other microbiomes predictably altered pH, fermentation product profiles (butyrate accumulation and acetate/lactate depletion), and population growth of other species including E. coli, thereby reshaping overall taxonomic composition. Our results suggest natural interindividual gut microbiome variation translates to variable ecological interactions with incoming bacteria, but these dynamics can be manipulated by a generalizable interspecies interaction.

In accordance with state policy on food security, the production of environmentally friendly agricultural products is a current priority. It is crucial to fully utilize the potential of all components of agroecosystems. The objective of this study was to evaluate the feasibility of using plant growth regulators based on natural humic substances to enhance the competitiveness of various potato hybrids grown in the Chechen Republic. The study was conducted in 2024-2025 in the forest-steppe zone of the Chechen Republic. The use of a growth regulator for pre-planting treatment of tubers contributed to a significant reduction in species diversity and the number of non-target species in potato crops. The use of a growth regulator in potato cultivation technology for the Queen Anna variety significantly reduced the pigment content in weed leaves. Thus, compared with the minimum and maximum infestation (256 pcs/m2), the chlorophyll a content decreased by 2.1 times, chlorophyll b by 2.6 times, and carotene by 1.8 times. This suggests intraspecific and interspecific competition in the agrocenosis of various early potato varieties. An inverse correlation was established between the weight of a single weed specimen and the number of weeds per 1 m2. Pre-planting treatment of potato tubers with a 0.1% solution of the humic-based growth regulator Humate+7 has been shown to have a positive effect on increasing the competitiveness of potato tubers. Based on the above, the feasibility of using Humate+7, a growth regulator based on natural humic substances, for pre-plant treatment of tomato seeds is beyond doubt.

Abstract Background Heavy metal pollution, a pervasive and persistent environmental stressor often linked to industrial and agricultural activities, interacts with intra- and interspecific competition as key factors influencing the invasion of exotic plants. Alternanthera philoxeroides and Trifolium repens exhibit distinct allocation strategies to mitigate resource competition under cadmium (Cd) pollution, yet their differential resistance to Cd remains underexplored. Results In this study, a greenhouse experiment was conducted to investigate the effects of Cd contamination and competitive interactions on the stress resistance index (SRI) and adaptive strategies of both species. The results indicated that T. repens exhibited higher SRI under stronger interspecific competition, demonstrating clear density dependence. T. repens primarily enhanced its competitiveness by increasing photosynthesis capacity, though its root system structure contributed more substantially to SRI. In contrast, A. philoxeroides increased SRI by forming shorter and thicker root system. Conclusion Overall, the root utilization strategy of A. philoxeroides showed greater advantages than that of T. repens . Under intraspecific competition, A. philoxeroides improved competitiveness mainly through increased root complexity and optimized photosynthetic efficiency via non-stomatal regulation in light competition. The invasiveness of A. philoxeroides can be attributed to the ability to synergistically combine root development and photosynthesis to enhance its stress resistance. This study provides a broader perspective on invasion mechanisms in natural ecosystems and offers a solid theoretical basis for understanding stress tolerance and environmental management of A. philoxeroides .