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The article explores the phenomenon of "dear enemy effects" in the stoplight parrotfish, Sparisoma viride. Dear enemy effects refer to the tendency of territory holders to act less aggressively towards their neighbors compared to strangers. The study observed territorial interactions between male parrotfish and neighboring males or nonterritorial "floaters." The results showed that territorial males were more likely to engage in escalated chases with floaters than with neighbors. The study suggests that the dear enemy effect may be influenced by the defense of food resources and the presence of females. The findings contribute to understanding the mechanisms underlying territoriality in parrotfish and its role in population regulation and ecosystem functioning. [Extracted from the article]

In Amazonian streams, damming caused by road construction changes the system's hydrological dynamics and biological communities. We tested whether the degree of specialization in fish (Bryconops giacopinii) individuals is higher in pristine stream environments with intact ecological conditions than in streams dammed due to the construction of a highway in the Amazon rainforest. To achieve this, stomach content data and stable isotopes (δ13C and δ15N) in tissues with varying isotopic incorporation rates (liver, muscle, and caudal fin) were used to assess the variation in consumption of different prey over time. The indices within‐individual component (WIC)/total niche width (TNW) and individual specialization were employed to compare the degree of individual specialization between pristine and dammed streams. The condition factor and stomach repletion of sampled individuals were used to infer the intensity of intraspecific competition in the investigated streams. The species B. giacopinii, typically considered a trophic generalist, has been shown to be, in fact, a heterogeneous collection of specialist and generalist individuals. Contrary to our expectations, a higher degree of individual specialization was detected in streams dammed by the highway. In dammed streams, where intraspecific competition was more intense, individuals with narrower niches exhibited poorer body conditions than those with broader niches. This suggests that individuals adopting more restricted diets may have lower fitness, indicating that individual specialization may not necessarily be beneficial for individuals. Our results support the notion that intraspecific competition is an important mechanism underlying individual specialization in natural populations. Our results suggest that environmental characteristics (e.g., resource breadth and predictability) and competition for food resources interact in complex ways to determine the degree of individual specialization in natural populations. [ABSTRACT FROM AUTHOR]

Aim: Wallacea is a global biodiversity hotspot and Sulawesi is the largest island in this region, notable for a high proportion of endemic species. The Wakatobi archipelago, off the southeastern peninsular arm of Sulawesi, is home to several endemic bird species. Although islands are known to influence the morphology of their resident species, competitive interactions also exert strong influences on morphology. Here, we consider the contributions of both islands and competitors on two morphological traits of two bird species in a small passerine guild found on the Wakatobi islands. Location: Wakatobi archipelago, Sulawesi Tenggara, Indonesia. Taxon: Wakatobi White‐eye (Zosterops flavissimus) and Wakatobi Sunbird (Cinnyris infrenatus). Methods: Working with morphological measures (from netting studies), population density metrics (from transect surveys) and fundamental data from islands (area, distance from mainland and elevation), we investigated (by means of multiple linear regression) which terms best explained variation in the body size and bill size of two small passerine birds endemic to the Wakatobi islands. Results: Both island metrics and competitor presence/density were useful in describing the variation in body size of both bird species. However, only competitor presence/density was useful in describing variation in bill size of the birds. The best models describing variation in these traits included terms representing both interspecific and intraspecific competition. Main Conclusions: Our findings indicate that simple island metrics may be useful in predicting some of the variation in some functional traits of island species. However, in this example, simple island metrics were insufficient to explain the full variation in body size of endemic birds across the Wakatobi archipelago and were of no use in predicting the variation in their bill size. As bill morphology frequently dictates diet and feeding niche, it is a trait which may determine population divergence and speciation. If simple island metrics fail to describe such diversification, it is surely important to capture that information in other ways. [ABSTRACT FROM AUTHOR]

Intraspecific competition can significantly alter the foraging behavior of social insects. How competition might impact closely located colonies with overlapping foraging ranges is largely unknown. Between August–November 2022 and September–November 2023, we investigated the intraspecific competition of three Aphaenogaster species (A. famelica, A. schurri, and A. japonica) in two urban forests in Kunming, China. We estimated the density of ant nest openings and measured foraging distances. Nest opening density was 0.18/m2 (0.33/m2 for A. famelica, 0.03/m2 for A. schurri, and 0.07/m2 for A. japonica), and mean foraging range was 160 cm (124 cm for A. famelica, 296 cm for A. schurri, and 228 cm for A. japonica). We then ran a series of field experiments to assess the effects of distance, food load, and intraspecific competition on ant foraging. For 36 pairs of nest openings, we placed one light and one heavy tuna bait at various distances between neighboring nest openings. We modified competition intensity by physically blocking one of the nest openings and analyzed time spent on food discovery, removal, and retrieval by ant workers. Ants spent a longer time discovering baits located farther away from, and retrieving heavier or farther baits. Blocking was correlated with a longer time for food removal (for A. schurri/japonica and A. famelica) and transportation (for A. famelica). Selectivity of the light vs heavy bait was not found, suggesting neighborhood distance was too short to generate distance-based selectivity patterns. Differences in nest spacing might be related to species-specific traveling and intraspecific competition. [ABSTRACT FROM AUTHOR]

Interspecific competition is an important factor in the population dynamics and geographical distribution of insect populations. Fall armyworm (FAW), Spodoptera frugiperda, an invasive species, and the Asian corn borer (ACB), Ostrinia furnacalis, a native pest species are major pests on maize in China, posing a threat to maize yield and grain quality. A series of laboratory, greenhouse, and field experiments were conducted to elucidate the competitive interactions between FAW and ACB. In the laboratory experiments, FAW exhibited aggressive behaviors more frequently when compared with ACB, while the latter species exhibited defense behaviors more frequently. Higher intraspecific competition was recorded in the FAW conspecific rather than in ACB, particularly in the 6th larval stage. FAW had a higher interspecific competitive advantage through intraguild predation over ACB, resulting in partial or complete displacement ACB when initially the ratio of the 2 species was 1 : 1. The interspecific competition also had significantly influenced on the population parameters, defensive enzymes, and nutrient of these 2 species. Competitive interaction proved that the response of superoxide, catalase, and soluble protein in FAW were significantly increased, whereas the total sugar content in both species was substantially decreased. Survival rate, and the plant damage that co‐infested by both species varied significantly among the sequential combinations under greenhouse and field conditions. FAW consistently exhibited stronger intraspecific aggression than ACB under laboratory and field conditions when co‐existing on the same feeding guild. These findings contribute to efforts toward the improvement of integrated pest management programs for FAW, in decision making for invasive and native pests' management strategies to reduce the high risks of FAW and ACB outbreaks. [ABSTRACT FROM AUTHOR]

Abstract Background Wolbachia-infected thelytokous Trichogramma wasps have been considered as potential effective biocontrol agents against lepidopteran pests in agriculture and forests. However, intra-specific competition may arise when Wolbachia-infected thelytokous Trichogramma coexist with their uninfected bisexual counterparts in fields or during mass-rearing procedures. This competition could potentially impact the efficacy of Trichogramma females in biological control programs. Results This study examined the parasitic capacities of bisexual (TdB) and Wolbachia-infected thelytokous (TdT) strains of Trichogramma dendrolimi as influenced by host density (ranging from 5 to 70 host eggs) and wasp density (two, four, and six females per arena). The experiments involved inter-strain competition between TdB and TdT strains (Inter-Td) as well as intra-strain competition within the TdT (Intra-TdT) or TdB (Intra-TdB) strains. Results revealed that females in the Inter-Td group exhibited a higher attack rate compared to those in the Intra-TdT and Intra-TdB groups, irrespective of wasp density. Specifically, when six females were present, the Inter-Td group showed significantly shorter host handling times than the Intra-TdT group. Within intra-strain cohorts, TdT females displayed a lower attack rate than TdB females when four or six females were present, and longer host handling times when six females were present. Mutual interference between individuals was not affected by competition types. Females of the Inter-Td group exhibited a higher probability of superparasitism than those of the Intra-TdB group or Inter-Td group. When both strains coexisted, the proportion of TdT offspring with six females was higher than that with two females or four females. Male ratios of bisexual offspring in Inter-Td groups were higher than those in Intra-TdB groups. The male ratio of bisexual offspring in the Inter-Td group increased with wasp density. Conclusions Our study highlights the negative impact of Wolbachia on parasitic capacity of Trichogramma females, increasing the likelihood of superparasitism. The coexistence of both strains enhances total parasitic efficacy, albeit resulting in a higher proportion of male offspring compared to scenarios with only uninfected females. The results will provide the reference for the usage of Wolbachia-infected thelytokous strain of T. dendrolimi in augmentative biological control programs.

Understanding the biodiversity–productivity relationship (BPR) is crucial for biodiversity conservation and ecosystem management. While it is known that diversity enhances forest productivity, the underlying mechanisms at the local neighborhood level remain poorly understood. We established a 9.6 ha dynamic forest plot to study how neighborhood diversity, intraspecific competition, and interspecific competition influence tree growth across spatial scales using linear mixed-effects models. Our analysis reveals a significant positive correlation between neighborhood species richness (NSR) and relative growth rate (RGR). Notably, intraspecific competition, measured by conspecific neighborhood density and resource competition, negatively impacts RGR at finer scales, indicating intense competition among conspecifics for limited resources. In contrast, interspecific competition, measured by heterospecific density and resource competition, has a negligible impact on RGR. The relative importance of diversity and intra/interspecific competition in influencing tree growth varies with scale. At fine scales, intraspecific competition dominates negatively, while at larger scales, the positive effect of NSR on RGR increases, contributing to a positive BPR. These findings highlight the intricate interplay between local interactions and spatial scale in modulating tree growth, emphasizing the importance of considering biotic interactions and spatial variability in studying BPR. [ABSTRACT FROM AUTHOR]

Aim: Invasive plants may evolve a suite of distinctive traits during spread in the new range. Among these traits, dispersal ability is an important trait determining the invasion speed of exotic plants. There is evidence that higher dispersal ability is favoured at the invasion front, where population density may be low. However, no study has explicitly tested how planting density in a common garden affects the dispersal ability of invasive plants. Location: Hainan island of China. Methods: In this study, using 27 populations of an invasive plant, Mikania micrantha, which is expanding its range on Hainan island of China, we examine how three dispersal‐related traits (i.e. dispersal ability, fruit mass, and pappus radius) change with distance from invasion centre and field population density, and how planting density in a common garden affects dispersal traits. Results: Dispersal traits did not change with distance from the invasion centre and field population cover either in the natural environment or in the common garden. In the common garden, increasing planting density from one to five plants per pot increased fruit mass and decreased dispersal ability, indicating that the effect of density on dispersal traits could not be detected in the field. The relationship between dispersal ability in the natural environment and that in the common garden was positive but significant only under the five plants per pot treatment, possibly because dispersal traits in natural conditions were selected under high‐density growth conditions. Main Conclusions: Our results indicate that increasing population density may increase fruit mass and reduce the dispersal ability of range‐expanding invasive plants. We suggest that further studies exploring the patterns of dispersal traits in range‐expanding invasive plants in a common garden should consider intraspecific competition. [ABSTRACT FROM AUTHOR]

Myzostoma khanhkhoaense is a cyst-to-free-moving myzostomid associated with the comatulid crinoid Clarkcomanthus albinotus. It induces deformations of the skeletal elements of the host's arms, thereby making protective "baskets" in which to hide from predators. Each "basket" is inhabited by a dense aggregation up to 25 worms of different sizes. The size-abundance structure of some subpopulations (these being defined as the inhabitants of one host) shows a clear peak, which may be related to the worm's reproductive cycle. Some subpopulations show two such peaks, which may be evidence of colonization by two different generations of worms. No subpopulations with more than two peaks were found, what is probably an indication that these worms have a short lifetime. We believe that a newly settled generation of M. khanhkhoaense undergoes no more than two reproductive cycles, starting with initial settlement, growth, and reproduction, and then — evident as the larger-size peak if a second generation of larvae settles on the same host — another round of growth and reproduction, and finally death. [ABSTRACT FROM AUTHOR]

Territorial defence depends on highly interrelated factors such as food abundance and conspecific density. We used Dupont's Lark Chersophilus duponti as a model species to evaluate the response of a territorial bird to a foreign male playback, examining how conspecific density, habitat quality and male body condition impact responses. The study was conducted in central Spain with variable male density. Response (yes/no), latency time, distance to the playback speaker, and the number of songs and other vocalizations were monitored for 5 min. Habitat quality was estimated using BlueNDVI vegetation index extracted from high‐resolution drone imagery, which is a proxy for arthropod prey biomass. Conspecific density (Kernel Density Estimator) and male body condition were calculated to assess their effect on response and intensity. We applied generalized linear mixed models (GLMMs) to determine which factors predicted the response and its intensity. There was a greater response probability in areas with a higher density of conspecifics and in areas of poorer habitat quality (i.e. lower BlueNDVI values). In contrast, latency time was longer in areas with lower conspecific density. Intrasexual communication (singing and calling rates) increased with habitat quality. Intraspecific communication (other vocalizations) increased in poorer quality habitats and at a higher density of conspecifics. Body condition was not related to any variables. Our results suggest that male density, sometimes used as an indicator of an area being well conserved for the species, may reflect areas of poorer habitat quality occupied by unpaired floater males, whereas paired territorial males would occupy and defend higher quality areas, leading to lower density. [ABSTRACT FROM AUTHOR]

Male–male combat occurs in many snake species and is often thought to result from competition for mates. We argue a more thorough assessment of the contexts in which combat occurs is warranted for snakes. We made field video observations of Agkistrodon conanti in central Florida, A. piscivorus in eastern North Carolina, and A. contortrix in eastern Kentucky. These observations were made in frequently used foraging sites; near drying ephemeral ponds in Florida and North Carolina and in a forested area with abundant emerging cicadas in Kentucky. In all three populations, males engaged in ritualized combat. In four instances, a variety of lines of evidence including season, local food resource abundance, local female abundance, and postcombat behaviors all indicated that access to food resources, rather than mating opportunities, was the catalyst for agonistic behavior. Behaviorally, food-induced combat appears nearly identical to mating-induced combat. Simplistic assumptions about the environmental contexts that induce combat may lead researchers to make inaccurate conclusions concerning the duration of the breeding season and the frequency of intraspecific competition for food in snake species. We outline a rigorous set of criteria that should be used to determine the context of male–male combat bouts. Videos showing the examples of combat discussed are available at http://www.momo-p.com/showdetail-e.php?movieid=momo231230ac01a, http://www.momo-p.com/showdetail-e.php?movieid=momo231230ac02a, http://www.momo-p.com/showdetail-e.php?movieid=momo231228ap01a, and http://www.momo-p.com/showdetail-e.php?movieid=momo231230ap01a. [ABSTRACT FROM AUTHOR]

Resource partitioning is considered a key factor in alleviating competitive interactions, enabling coexistence among consumer species. However, most studies have focused on resource partitioning between species, ignoring the potentially critical role of intraspecific variation in resource use. We investigated floral resource partitioning across species, colonies, and individuals in a species‐rich bumblebee community in the diversification center of bumblebees. We used a total of 10,598 bumblebees belonging to 13 species across 5 years in the Hengduan Mountains of southwest China. First, we evaluated the influence of a comprehensive set of floral traits, including both those related to attractiveness (flower color and shape) and rewards (pollen, sugar ratio, nectar volume, sugar concentration, and amino acid content) on resource partitioning at the species level in bumblebee–plant networks. Then, we explored intraspecific resource partitioning on the colony and individual levels. Our results suggest that bumblebee species differ substantially in their use of the available floral resources, and that this mainly depends on flower attractiveness (floral color and shape). Interestingly, we also detected floral resource partitioning at the colony level within all commonest bumblebee species evaluated. In general, floral resource partitioning between bumblebee individuals decreased with species‐ and individual‐level variation in body size (intertegular span). These results suggest that bumblebee species may coexist via the flexibility in their preferences for specific floral traits, which filters up to support the co‐occurrence of high numbers of species and individuals in this global hotspot of species richness. [ABSTRACT FROM AUTHOR]

Asexual organisms are ubiquitous. While being members of a single species with the same ecological requirements, multiple asexual genotypes within a species are often found in a single habitat. Niche partitioning in time and space among genotypes has been proposed to explain this phenomenon. However, it is not clear whether these different genotypes co‐occur in the long term.Therefore, we examined the population dynamics of two asexual Daphnia cf. pulex genotypes (JPN1 and JPN2) over 9 years in a small mountain lake. These two genotypes consistently occurred in the same seasons and layers, suggesting that niche partitioning cannot explain their long‐term co‐occurrence. The abundance of JPN1 was typically higher in most years. However, the abundance of dormant eggs in lake sediments was at the same level between the genotypes.Results of a laboratory experiment showed that JPN1 competitively excluded JPN2. However, many JPN2 individuals produced dormant eggs before JPN1 competitively excluded them from the experiment. Furthermore, the competitively inferior JPN2 produced dormant eggs abundantly in the medium containing a crowding cue from JPN1 while no such trend was observed for JPN1.These results showed that a competitively inferior asexual genotype could maintain a population with a competitively superior genotype for a long period of time because it had the ability to detect an increase in competitors and produce dormant eggs each year before being competitively eliminated.Based on these results, we suggest that the variation in genotype‐specific response in dormant egg production to environmental change plays a key role in the long‐term co‐occurrence of different asexual genotypes in single habitats. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The aim of this study is to assess the impact of various row spacings on the morphology, components of grain yield, and overall grain yield of soybean. The experiments were conducted over two planting seasons (2014/2015 and 2015/2016) using two planting dates (November and December) and two cultivars, FPS Urano RR and BMX Tornado RR. The row spacings tested were: 45 cm (wide row), 45 × 45 cm (cross row), 22.5 × 45 cm (twin row), and 22.5 cm (narrow row). Measurements included leaf area index and sunlight interception at R2 stage, as well as grain yield components and overall grain yield. Narrow rows, in addition to achieving canopy closure, also demonstrated enhanced sunlight interception at the R2 stage. However, the positive effect of increased sunlight interception on grain yield was only significant for the December planting date, with no notable difference observed for the November planting date. These findings imply that while narrow rows may offer advantages, particularly in later planting dates, their implementation should be carefully considered and may not consistently lead to increased grain yield, reinforcing the continued preference for conventional row spacing.

The Skellam model describes discrete‐time population dynamics of a single species assuming uniform (i.e., random or Poissonian) individual distribution and intraspecific contest competition. Apart from studies on individual‐based models derived from first principles it has been rarely applied in ecological research although in specific situations it may be more appropriate than, for instance, the frequently used Ricker model, which is derived assuming scramble competition among the individuals. In this article, we offer an insight into the first principles underlying the Skellam model and provide an alternative parameterization of the model in terms of two commonly used parameters: intrinsic rate of population increase and carrying capacity. We also provide guidelines and software for fitting the Skellam model to discrete population time series data. In light of these findings, the Skellam model may be a useful alternative for a range of purposes where it has been earlier overlooked. [ABSTRACT FROM AUTHOR]

We consider a predator-prey system with strong Allee effect in prey and intraspecific competition in predator. We divide the parameter space into several mutually exclusive regions, and for each region we give a rather complete description of the global dynamics including equilibrium stability, Hopf bifurcation and its directions, existence of a heteroclinic orbit loop, a homoclinic orbit loop and limit cycles. In comparison with systems without the Allee effect in prey and systems without the intraspecific competition in predator, we find that the Allee effect in prey and the over-exploitation of the prey by the predator may drive the extinction of two species, but the intraspecific competition in the predator can generate "hydra effect" that regulates the population size of both predator and prey by suppressing the over-exploitation of prey, improving the probability of survivals of two species. [ABSTRACT FROM AUTHOR]

Interspecific competition is widely considered a powerful process underlying species coexistence and ecological community structure. Although coexistence theory predicts stronger competition between more ecologically similar species, empirical support has largely relied on inferring competition from patterns of species co-occurrence. Coexistence theory also posits that species can only coexist when individuals compete more with conspecifics than with other species, however, few field studies—particularly in reptiles—have simultaneously estimated the strength of both intra- and interspecific competition among co-occurring species. Using an array of 12 experimental plots, we manipulated species presence and population size by plot of three native Anolis lizard species to empirically estimate the strength of competition on one anole species driven by two other species of varying ecological similarity. We observed that the strength of competition—as determined by relative growth rates and gravidity—was highly predictable and correlated to ecological similarity. Interspecific competition was strongest among species of highest ecological similarity, and intraspecific competition—induced by the addition or removal of conspecifics—was consistently the most intense. By employing direct experimental manipulations, our study provides an empirical investigation of the strength of competition as it relates to ecological similarity. [ABSTRACT FROM AUTHOR]

Competition shapes species coexistence and community assembly, playing a central role in maintaining biodiversity and ecosystem resilience. Here, we used an asymmetric competition index that quantifies the possible competitive effect of a species on any other, using southern Aegean Sea nekton biomass from the Mediterranean International Trawl Survey dataset, combined with data on six traits relevant to trophic ecology and spawning. We modeled the effect of selected haul-level covariates on the competition index, and we indicated competition variation across depth and habitats. Most species experienced stronger inter- than intra-specific competition. Both the higher-than-expected significance of interspecific competition (in comparison to intraspecific that is generally anticipated to be higher) and the existence of an extensive network of multiple competitive interactions indicated, are associated with high biodiversity, combined to the absence of dominance by one or a few species in the community (no species is disproportionally highly abundant in comparison to others); the latter may be relevant to community stability and resilience. The quantification of competition across marine ecosystems can help predict how fish communities will respond to future resource availability and environmental conditions. [ABSTRACT FROM AUTHOR]

Summary: The Jornada Basin Long‐Term Ecological Research Site (JRN‐LTER, or JRN) is a semiarid grassland–shrubland in southern New Mexico, USA. The role of intraspecific competition in constraining shrub growth and establishment at the JRN and in arid systems, in general, is an important question in dryland studies.Using information on shrub distributions and growth habits at the JRN, we present a novel landscape‐scale (c. 1 ha) metric (the 'competition index', CI), which quantifies the potential intensity of competitive interactions. We map and compare the intensity of honey mesquite (Prosopis glandulosa, Torr.) competition spatially and temporally across the JRN‐LTER, investigating associations of CI with shrub distribution, density, and soil types.The CI metric shows strong correlation with values of percent cover. Mapping CI across the Jornada Basin shows that high‐intensity intraspecific competition is not prevalent, with few locations where intense competition is likely to be limiting further honey mesquite expansion.Comparison of CI among physiographic provinces shows differences in average CI values associated with geomorphology, topography, and soil type, suggesting that edaphic conditions may impose important constraints on honey mesquite and growth. However, declining and negative growth rates with increasing CI suggest that intraspecific competition constrains growth rates when CI increases above c. 0.5. [ABSTRACT FROM AUTHOR]

The trill elements of many bird species' songs have been hypothesized as honest signals of performance. However, the breadth of receiver responses to variation in the signaller's trill performance is unknown. We exposed wild male Lincoln's sparrows (Melospiza lincolnii) to two song treatments, one with low- and another with high-performance trills. We found no effect of treatment on measures of agonistic behaviour and song length. However, relative to the subjects' trills following the high-performance treatment, those following the low-performance treatment were elevated in performance due to trill types with high frequency bandwidth in the third trill of songs. Treatment also affected trill duration through its syllable count in a manner that varied by the song's trill number. Thus, the performance of a signal to which a receiver is exposed drives plasticity in his own performance in sequence-specific manner. Males may showcase their own performance in the presence of lower-performing rivals. [ABSTRACT FROM AUTHOR]

Explaining the physiological and ecological effects of wheat population density can provide new research methods for field crop production. A three-year field trial under drill single-seed seeding was conducted, which used three different intra-row seed-seedling spacings to quantitatively analyze the density effect from three perspectives—population, individual plant, and single-stem panicle—at the winter wheat harvest. The results showed that year and density had significant effects on both the population and individual plant yield (p < 0.05), as well as on some yield components and biomass indicators. The interaction between planting density and annual climate was found only in the number of grains for both the entire population and individual plants. With the increase in planting density, the CI gradually increased, inhibiting the growth of individual plants and leading to a negative impact on monoculture wheat yield. The drill single-seed seeding method can provide a basic experiment condition for analyzing the density effect. The density effect of wheat populations originates from intraspecific competition, which mainly affects the growth of individual plants. Research based on the analysis of density effects from the perspectives of population, individual plants, and single-stem panicles can provide a methodological reference for precision agriculture. [ABSTRACT FROM AUTHOR]

The success of an organism depends on the molecular and ecological adaptations that promote its beneficial fitness. Parasitoids are valuable biocontrol agents for successfully managing agricultural pests, and they have evolved diversified strategies to adapt to both the physiological condition of hosts and the competition of other parasitoids. Here, we deconstructed the parasitic strategies in a highly successful parasitoid, Trichopria drosophilae, which parasitizes a broad range of Drosophila hosts, including the globally invasive species D. suzukii. We found that T. drosophilae had developed specialized venom proteins that arrest host development to obtain more nutrients via secreting tissue inhibitors of metalloproteinases (TIMPs), as well as a unique type of cell—teratocytes—that digest host tissues for feeding by releasing trypsin proteins. In addition to the molecular adaptations that optimize nutritional uptake, this pupal parasitoid has evolved ecologically adaptive strategies including the conditional tolerance of intraspecific competition to enhance parasitic success in older hosts and the obligate avoidance of interspecific competition with larval parasitoids. Our study not only demystifies how parasitoids weaponize themselves to colonize formidable hosts but also provided empirical evidence of the intricate coordination between the molecular and ecological adaptations that drive evolutionary success.

The aim of this study is to assess the impact of various row spacings on the morphology, components of grain yield, and overall grain yield of soybean. The experiments were conducted over two planting seasons (2014/2015 and 2015/2016) using two planting dates (November and December) and two cultivars, FPS Urano RR and BMX Tornado RR. The row spacings tested were: 45 cm (wide row), 45 × 45 cm (cross row), 22.5 × 45 cm (twin row), and 22.5 cm (narrow row). Measurements included leaf area index and sunlight interception at R2 stage, as well as grain yield components and overall grain yield. Narrow rows, in addition to achieving canopy closure, also demonstrated enhanced sunlight interception at the R2 stage. However, the positive effect of increased sunlight interception on grain yield was only significant for the December planting date, with no notable difference observed for the November planting date. These findings imply that while narrow rows may offer advantages, particularly in later planting dates, their implementation should be carefully considered and may not consistently lead to increased grain yield, reinforcing the continued preference for conventional row spacing. [ABSTRACT FROM AUTHOR]

Animals with large energy requirements are forced to optimize their hunting strategy, which may result in differentiation of the diet between sexes and across seasons. Here, we examined spatiotemporal variation in the diet of both sexes of the Pond Bat Myotis dasycneme , a species known to have spatial segregation of sexes when the young are born and lactating. Fecal pellets were collected from live animals for a period of 15 years at various locations in the Netherlands. A total of 535 pellets were successfully analyzed by microscopy and an additional 160 pellets by DNA metabarcoding. Morphological and molecular analyses showed that the diet of pregnant and lactating pond bats differed significantly from the diet of females with no reproductive investment. Further analyses of the data showed that pregnant female pond bats are highly dependent on small prey and pupae, mainly nonbiting midges and mosquitoes (Diptera: Chironomidae and Culicidae). These insects can be found in large quantities in peatlands intersected with shallow waterways, the habitat type in which female pond bats were observed more often than males. Our results suggest that during pregnancy the spatial segregation of sexes coincides with sex-specific diets, which might reflect habitat selection based on energy requirements, in addition to lowered intraspecific competition. [ABSTRACT FROM AUTHOR]

Background and aims: According to the nitrogen-disease hypothesis, plant diseases will become more serious with the aggravation of global nitrogen (N) deposition. Numerous studies have indicated that Epichloë endophytes can enhance host plant resistance to pathogens. It is unclear how the competitive ability of endophyte-infected (EI) over endophyte-free (EF) plants changes under the interference of N deposition and plant disease. Methods: In this study, Achnatherum sibiricum, native to the Inner Mongolia steppe of China, was used as experimental material. We experimentally manipulated N addition and pathogen inoculation and examined the growth and competition between EI and EF A. sibiricum. Results: The results showed that EI plants had a greater competitive advantage than EF plants under low N conditions, and this advantage decreased with the N supply. When high N and pathogens were both present, pathogen inoculation reversed the adverse effects of high N supply on the competitive advantage of EI A. sibiricum. Epichloë endophytes not only reduced the disease of EI plants but also reduced the disease of neighboring EF plants. Meanwhile, Epichloë endophytes changed the response of the host disease to N. The disease index of EF plants increased with increasing leaf N content, while that of EI plants did not change. Conclusion: This study highlights that under the dual factors of N deposition and pathogen infection, endophytic fungi improve the competitive ability of host plants. Our results show that considering both biotic and abiotic factors is crucial for predicting the dominance of plant-fungal symbionts in the community. [ABSTRACT FROM AUTHOR]

Individuals across various animal species communicate their presence to conspecifics. Especially phytophagous and parasitoid insects with their brood developing on limited resources rely on chemical cues, such as host-marking pheromones, to reduce intraspecific competition. Bark beetles are phytophagous insects with some species being economically and ecologically relevant forest pests. Several of them use the volatile compound verbenone to inhibit attraction and reduce intraspecific competition. However, in the Eurasian spruce bark beetle, Ips typographus (L.), temporal emission patterns did so far not quite support the putative function of verbenone as an indicator of densely colonised host trees. More importantly, it is currently unclear how well verbenone emission is actually related to colonisation density and thus intraspecific competition. Here, we inoculated Norway spruce logs with I. typographus at two defined colonisation densities in the greenhouse and measured the emission of verbenone and its precursors α-pinene and verbenol over time. Verbenone emission was 3–7 times greater from colonised logs compared to decaying logs without beetles during the major part of larval development. Furthermore, our data supports the quantitative hypothesis, that the termination of attack on a tree is mediated by a cessation of the release of verbenol and continuous emission of verbenone. The latter is most likely a passively produced host-marking cue reflecting the actual density of conspecifics since per-beetle emission was unaffected by colonisation density. These findings shed new light on the regulation of bark beetle mass aggregations, which are currently causing previously unseen economic damages in temperate forests. [ABSTRACT FROM AUTHOR]

Territoriality is a behavioural adaptation resulting from intraspecific competition and reflects the strategy of how individuals share limited resources in the environment. As a consequence, territorial contests and levels of aggressiveness are strongly influenced by population density.The positive relationship between population density and the intensity of intraspecific competition may appear straightforward. However, empirical evidence regarding this association remains inconclusive. This ambiguity may be attributed to studies that have predominantly focussed on specific fight‐associated traits while overlooking potential interactions between multiple phenotypic characteristics and population dynamics.To examine the effects of population density and other ecological factors on the variation in fight behaviour as well as fight‐associated morphology and performance. We conducted population surveys and behavioural experiments using the Swinhoe's tree lizard across eight populations.Our findings revealed that males from higher density populations tended to engage in less intense fights and exhibited a weaker resident advantage in fights, which coincided with our findings on lower rates of injuries, weaker bite forces and smaller body sizes (and vice versa). Male‐specific variation in fight behaviour, morphology and performance along a density gradient suggests different evolutionary equilibria in territoriality influenced by local costs and benefits.Our study supports the significant role of negative density dependence as a fundamental regulator of eco‐evolutionary dynamics. The observed phenotypic variation emphasizes the importance of ecological and social factors in shaping ontogenetic growth and life‐history strategies. Our findings provide a basis for future investigations into pace‐of‐life syndromes and shed light on how phenotypic adaptation may shape population structure. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Intraspecific competition in even-aged populations of plants and animals is very rarely the subject of ecological research. Even more rarely are ecologists interested in the important outcomes of this competition - the unequal partitioning of resources for which competition takes place and the resulting from it individual variability in the growth rate of individuals, their survival rate and the production of offspring. There are various reasons for this. The statistical methods used by ecologists deal with average values. Classical models of mathematical ecology describe the dynamics of the densities of populations, and are therefore interested in variables that by their nature neglect the important fact that a population is made up of individuals. It is also not without significance that it is generally very difficult to study interactions between individuals. The present study aims to discuss some very simple examples of how individual variability in the amount of resources taken up by individuals from the environment can arise because of the physical nature of these resources, without considering interactions between individuals. Three examples will be presented: individuals of a phytoplankton species that move chaotically in a column of water illuminated from above, sedentary organisms randomly distributed on a two-dimensional plane, and predators hunting for food in the form of particles. In all these examples, the measures of resources obtained by individuals indicate the existence of individual variability, and their distributions have a positive skewness (there are more individuals that obtained few resources than individuals with many resources). The influence that the costs of obtaining resources from the environment and interactions between individuals may have on such form of individual variability will be discussed also. [ABSTRACT FROM AUTHOR]

Predation is a major evolutionary force determining life‐history traits in prey by direct and indirect mechanisms. This study focuses on life‐history trait variation in crucian carp (Carassius carassius), a species well known for developing a deep body as an inducible morphological defence against predation risk. Here, the authors tested variation in growth and reproductive traits in 15 crucian carp populations in lakes along a predation risk gradient represented by increasingly efficient predator communities. Lakes were located in south‐eastern Norway and were sampled in summer 2018 and 2019. The authors expected crucian carp to attain higher growth rate, larger size, and later age at maturity with increasing predation risk. In the absence of predators, they expected high adult mortality, early maturity and increased reproductive effort caused by strong intraspecific competition. They found that the life‐history traits of crucian carp were clearly related to the presence of piscivores: with increasing predation risk, fish grew in body length and depth and attained larger asymptotic length and size at maturity. This growth was evident at young age, especially in productive lakes with pike, and it suggests that fish quickly outgrew the predation window by reaching a size refuge. Contrary to the authors' predictions, populations had similar age at maturity. High‐predation lakes also presented low density of crucian carp. This suggests that fish from predator lakes may experience high levels of resource availability due to reduced intraspecific competition. Predation regulated life‐history traits in crucian carp populations, where larger size, higher longevity and size at maturity were observed in lakes with large gaped predators. [ABSTRACT FROM AUTHOR]

The relationship between a reptile and its thermal environment is a key feature of habitat use, which may be impacted by, among others, the requirements for food, avoidance of competitors and predators. Juvenile lizards are subject to the same ecological pressures, but may additionally experience predation or exclusion from prime basking site by adults and hence their capacity to achieve preferred body temperatures. In this paper, we examined basking site selection in juvenile western green lizards, Lacerta bilineata and compared them to basking site availability. Secondly, measurements of morning substrate temperatures at different basking sites were compared to basking site selection over the same period. The results indicated that juveniles selected substrates with fast heating surfaces, for example fallen branches for basking, in greater frequency than their availability but in even greater than expected frequency on the cooler surfaces of clusters of bramble plant. This finding contrasted with basking site selection in adult L. bilineata in a previous study where wood surfaces was preferred over non-wood surfaces whilst avoiding basking on bramble. This illustrates the different ecological requirements between adults and juveniles. [ABSTRACT FROM AUTHOR]

Simple Summary: The aphid Aphis gossypii Glover is a serious pest that inflicts severe damage upon goji berry plants in China. The current prevailing approach to pest prevention involves the utilization of chemical insecticides, which presents potential risks to both human health and the environment. The improper use of pesticides leads to the emergence of drug-resistant pests, thereby contributing to the resurgence of rampant pest populations. Therefore, the conservation and management of predators in agricultural ecosystems should receive increased attention, given their crucial role. Ladybirds have previously been identified as the primary predators of aphid species. However, their effectiveness as biological agents against aphids on goji berry plants remains uncertain. We found that the potential of ladybirds in controlling the aphid populations is promising, thus possibly making a contribution to environmental protection. By conducting an analysis of functional responses, intraspecific competition, and a semi-field study, we have determined that H. axyridis and C. septempunctata exhibit greater potential as biocontrol agents against aphids in comparison to H. variegata. Notably, future field studies will play a pivotal role in ensuring the effective implementation of a biological control program. The aphid, Aphis gossypii Glover, is identified as a significant pest that causes severe damage to goji berries in China. To analyze the ladybird consumption of aphids, the functional responses of three ladybird species, Harmonia axyridis, Coccinella septempunctata, and Hippodamia variegata, and intraspecific competition among ladybird individuals were evaluated under laboratory conditions. Moreover, the practical impact of ladybirds on aphid population reduction was investigated in semi-field conditions. We found that all adult ladybirds of the three species exhibited a type II functional response toward aphids. According to Holling's disc equation, H. axyridis exhibited the highest searching efficiency (a = 0.79), while C. septempunctata had the shortest handling time (Th = 5.07 min) among the three ladybird species studied. Additionally, intraspecific competition had a greater impact on H. variegata (m = 0.41) compared to the other two ladybird species. The semi-field study demonstrated that H. axyridis (83.9% reduction) and C. septempunctata (78.7% reduction) exhibited higher efficacy in reducing aphid populations compared to H. variegata (27.3% reduction). This study suggests that H. axyridis and C. septempunctata exhibit potential as effective biological control agents against aphids on goji berry plants and highlights the importance of considering intraspecific competition. However, the results obtained from laboratory and semi-field studies cannot be directly extrapolated to field conditions due to the simplification of these experimental systems. Future field studies are crucial in ensuring the effective implementation of a biological control program. [ABSTRACT FROM AUTHOR]

Understanding the biodiversity–productivity relationship (BPR) is crucial for biodiversity conservation and ecosystem management. While it is known that diversity enhances forest productivity, the underlying mechanisms at the local neighborhood level remain poorly understood. We established a 9.6 ha dynamic forest plot to study how neighborhood diversity, intraspecific competition, and interspecific competition influence tree growth across spatial scales using linear mixed-effects models. Our analysis reveals a significant positive correlation between neighborhood species richness (NSR) and relative growth rate (RGR). Notably, intraspecific competition, measured by conspecific neighborhood density and resource competition, negatively impacts RGR at finer scales, indicating intense competition among conspecifics for limited resources. In contrast, interspecific competition, measured by heterospecific density and resource competition, has a negligible impact on RGR. The relative importance of diversity and intra/interspecific competition in influencing tree growth varies with scale. At fine scales, intraspecific competition dominates negatively, while at larger scales, the positive effect of NSR on RGR increases, contributing to a positive BPR. These findings highlight the intricate interplay between local interactions and spatial scale in modulating tree growth, emphasizing the importance of considering biotic interactions and spatial variability in studying BPR.

In territorial raptors, breeding performance and foraging behaviour are affected by territory characteristics as the abundance and availability of different prey species varies between habitats. In this study, we examined the diet of two White-tailed Eagle pairs, occupying neighbouring territories in two adjacent inland lakes in Northern Greece. We assess the diet composition of the species in the southernmost part of its European range and evaluate any intraspecific differences in the diet that may reflect resource and/or niche partitioning between territories. We found that birds and specifically waterbirds comprise the largest and quantitatively most important part of the White-tailed Eagle´s diet, with fish being the second most important prey group that was only found in the nest remains from one territory. There was high diet overlap between the two territories and when considering only avian prey our results suggest that the species predates on heavier (and the most common) waterbird species. A main factor that could be driving differences in the abundance and availability of different prey species between territories could be lake physiography, as our results point to a segregation and a subsequent resource partitioning between territories, with each pair utilizing an adjacent lake and its associated habitats. Competition and territoriality therefore seem to be important intraspecific interactions that along with prey availability could promote changes in territory size and ultimately affect individual fitness.

Background: Understanding the role of species identity in interactions among individuals is crucial for assessing the productivity and stability of mixed forests over time. However, there is limited knowledge concerning the variation in competitive effect and response of different species along climatic gradients. In this study, we investigated the importance of climate, tree size, and competition on the growth of three tree species: spruce (Picea abies), fir (Abies alba), and beech (Fagus sylvatica), and examined their competitive response and effect along a climatic gradient. Methods: We selected 39 plots distributed across the European mountains with records of the position and growth of 5,759 individuals. For each target species, models relating tree growth to tree size, climate and competition were proposed. Competition was modelled using a neighbourhood competition index that considered the effects of inter- and intraspecific competition on target trees. Competitive responses and effects were related to climate. Likelihood methods and information theory were used to select the best model. Results: Our findings revealed that competition had a greater impact on target species growth than tree size or climate. Climate did influence the competitive effects of neighbouring species, but it did not affect the target species' response to competition. The strength of competitive effects varied along the gradient, contingent on the identity of the interacting species. When the target species exhibited an intermediate competitive effect relative to neighbouring species, both higher inter- than intraspecific competitive effects and competition reduction occurred along the gradient. Notably, species competitive effects were most pronounced when the target species’ growth was at its peak and weakest when growing conditions were far from their maximum. Conclusions: Climate modulates the effects of competition from neighbouring trees on the target tree and not the susceptibility of the target tree to competition. The modelling approach should be useful in future research to expand our knowledge of how competition modulates forest communities across environmental gradients.

Species management and conservation efforts are often based on range-wide trends, assuming dynamic equilibrium across space and time, even though fine-scale variability may be driving local dynamics. Oncorhynchus mykiss is a globally introduced, facultatively anadromous salmonid that is experiencing demographic shifts characterized by greater proportions of population remaining in freshwater. The degree of niche overlap between age classes of O. mykiss in freshwater environments may dictate how resources are partitioned within populations. We conducted a meta-analysis of age-specific O. mykiss habitat use to evaluate the degree of niche-partitioning between age classes and how age-specific habitat use relates to global in-stream and landscape level habitat variation. O. mykiss used deeper habitats as they grew towards maturity but did not partition habitat based on water velocity or substrate composition. As annual precipitation increased, O. mykiss used deeper and shallower habitats, and as summer air temperature increased, O. mykiss used shallower habitats. O. mykiss of native origin used deeper habitats than nonnative O. mykiss. However, a large proportion (42–99%) of variation in habitat use was associated with study or ecoregion, making climactic predictors unreliable for predictive species distribution or population dynamics models. Although the exact mechanisms driving geographic variability in O. mykiss habitat use are not fully understood, our results boost our understanding of how demographic shifts affect population resilience under climate change. Further research incorporating individual competitive behavior in predictive population models may elucidate the links between resource availability, demographic rates, and long-term O. mykiss population stability.

Competition among larval anurans can occur via interference as well as via a reduction in per-capita food supply. Previous research on intraspecific interference competition in cane toad (Rhinella marina) tadpoles found conflicting results, with one study detecting strong effects on tadpoles and another detecting no effects on metamorphs. A capacity to recover from competitive suppression by the time of metamorphosis might explain those contrasting impacts. In a laboratory experiment, we found that nine days of exposure to intraspecific interference competition strongly reduced tadpole growth and development, especially when the competing tadpoles were young (early-stage) individuals. Those competitive effects disappeared by the time of metamorphosis, with no significant effect of competition on metamorph body condition, size, larval period or survival. Temporal changes in the impact of competition were not related to tadpole density or to variation in water quality. The ability of larval cane toads to recover from intraspecific interference competition may enhance the invasive success of this species, because size at metamorphosis is a significant predictor of future fitness. Our study also demonstrates a cautionary tale: conclusions about the existence and strength of competitive interactions among anuran larvae may depend on which developmental stages are measured.

BACKGROUND: Intraspecific competition is shared in the insect world, especially under the condition of limited food and space resources. To avoid intraspecific competition and increase offspring survival, insects have evolved various effective strategies. A widely‐accepted tactic is employing chemical cues, which are frequently utilized as indicators of conspecific colonization. The sweet potato weevil (SPW), Cylas formicarius, is a destructive pest of sweet potatoes. Its larvae bore into sweet potatoes and alter the emission of odors. The present study aimed to investigate whether volatiles associated with SPW larvae feeding influence the behavioral preference of conspecific adults. RESULTS: Volatiles from SPW larvae‐infested sweet potatoes were collected by a head‐space method and analyzed using gas chromatography‐electroantennogram detector (GC‐EAD) and gas chromatography–mass spectrometry (GC–MS). Five compounds eliciting EAD responses from the antennae of both male and female adult SPW were identified from sweet potatoes with the third‐instar larvae, including linalool, citronellol, nerol, geraniol, and ipomeamarone. Four monoterpene alcohols significantly repelled SPW adults from feeding and oviposition at higher doses in the behavioral preference bioassays. Among them, geraniol displayed the strongest repellent activities for SPW feeding and oviposition. These results suggested that SPW larvae could reduce colonization of adult SPWs by inducing monoterpene alcohols, thereby avoiding intraspecific competition. CONCLUSION: The present study demonstrated that volatile monoterpene alcohols induced by SPW larvae are chemical cues of larvae occupation for SPW adults to change their behavioral preference. Unveiling factors that mediate avoidance of intraspecific competition could help develop repellents or oviposition deterrents for SPW control. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Competition typically takes place in a spatial context, but eco-evolutionary models rarely address the joint evolution of movement and competition strategies. Here we investigate a spatially explicit forager-kleptoparasite model where consumers can either forage on a heterogeneous resource landscape or steal resource items from conspecifics (kleptoparasitism). We consider three scenarios: (1) foragers without kleptoparasites, (2) consumers specializing as foragers or as kleptoparasites, and (3) consumers that can switch between foraging and kleptoparasitism depending on local conditions. We model movement strategies as individual-specific combinations of preferences for environmental cues, similar to step-selection coefficients. Using mechanistic, individual-based simulations, we study the joint evolution of movement and competition strategies, and we investigate the implications for the distribution of consumers over this landscape. Movement and competition strategies evolve rapidly and consistently across scenarios, with marked differences among scenarios, leading to differences in resource exploitation patterns. In scenario 1, foragers evolve considerable individual variation in movement strategies, while in scenario 2, movement strategies show a swift divergence between foragers and kleptoparasites. In scenario 3, where individuals' competition strategies are conditional on local cues, movement strategies facilitate kleptoparasitism, and individual consistency in competition strategy also emerges. Even in the absence of kleptoparasitism (scenario 1), the distribution of consumers deviates considerably from predictions of ideal free distribution models because of the intrinsic difficulty of moving effectively on a depleted resource landscape with few reliable cues. Our study emphasizes the advantages of a mechanistic approach when studying competition in a spatial context and suggests how evolutionary modeling can be integrated with current work in animal movement ecology. [ABSTRACT FROM AUTHOR]

Insular populations of mammals have been shown to undergo drastic morphological changes relative to mainland counterparts, and these adaptations can provide insight into the evolutionary effects of predation and competition. Selection has been shown to favor more energetically efficient body plans in insular mammals, even when this entails the reduction of anti-predator defenses, but few studies have focused on morphological effects within the same species. Previous research has established that insular large mammals tend to reduce in body size, and that size reduction may not scale isometrically across all body parts. The brain has been a particular subject of interest due to its high energy requirements. Here, we report that an extant, dwarfed island population of black-tailed deer (Odocoileus hemionus columbianus) exhibits significantly reduced brain mass relative to body mass in comparison to their mainland conspecifics, with brain mass 4.9% smaller in the island population for a given body mass. Further, in the dwarfed population, orbital area was 4.1% smaller for a given body mass, but this reduction was not significant. Foramina magna reduced isometrically. In resource-limited insular environments, negative allometry of the brain is consistent with predictions of reduced investment in energetically costly organs. This study is, to our knowledge, the first to examine the morphological effects of insularity on brain size in two conspecific populations, and these findings suggest that selection toward reduced brain size may act relatively quickly after isolation. [ABSTRACT FROM AUTHOR]

Environments experienced by parental plants may potentially influence the performance of their offspring. These effects may also vary depending on the current environment experienced by the offspring. However, whether these transgenerational effects, especially those induced by biotic factors such as competition, can persist for multiple generations has not been tested. Here, we examined intraspecific competition‐induced transgenerational effects across multiple generations using a floating clonal plant Spirodela polyrhiza, by growing three successive generations each under either low or high density. The second‐generation offspring performed better when the first‐generation plants were grown under low than under high density, independently of the density experienced by the second generation. The third‐generation offspring performed better under low than under high density, and the difference was more pronounced when the second‐generation plants were grown under low density. Moreover, the density of the first and second generation interacted to influence the morphology of the third‐generation offspring. These results indicate that competition‐induced transgenerational effects in S. polyrhiza can vary depending on the competition environment of its offspring and that these effects can persist across multiple generations. [ABSTRACT FROM AUTHOR]

Interspecific competition from introduced and naturally colonizing species has potential to affect resident populations, but demographic consequences for vertebrates have rarely been tested. We tested hypotheses of interspecific and intraspecific competition for density, body mass, and fertility of adult female Roe Deer (Capreolus capreolus) across a heterogeneous forest landscape occupied by two introduced deer species: Mediterranean Fallow Deer (Dama dama); and subtropical Reeve's Muntjac (Muntiacus reevesi). Species-specific deer densities in buffers around culling locations of 492 adult female Roe Deer, sampled over seven years, were extracted from spatially explicit models calibrated through annual nocturnal distance sampling. Roe Deer fertility and body mass were related to species-specific deer densities and extent of arable lands using piecewise structural equation models. Reeve's Muntjac density was lower at higher Fallow Deer densities, suggesting interspecific avoidance via interference competition, but greater when buffers included more arable land. Roe Deer body mass was marginally greater when buffers included more arable land and was independent of deer densities. However, Roe Deer fertility was unrelated to female body mass, suggesting that fertility benefits exceeded an asymptotic threshold of body condition in this low-density population. However, Roe Deer fertility was slightly greater rather than reduced in areas with greater local Roe Deer density, suggesting negligible intraspecific competition. In contrast, Roe Deer was less fertile in areas with greater Reeve's Muntjac densities; thus, interspecific exceeded intraspecific competition in this assemblage. In contrast, we found no support for any effects of Fallow Deer density on Roe Deer density, body mass, or fertility. Complex networks of interspecific competition operating in this deer assemblage include: interspecific interference from Fallow Deer exceeded habitat effects for Reeve's Muntjac; and interspecific competition from introduced, smaller sedentary Reeve's Muntjac reduced fertility, unlike intraspecific, or potential competition with larger, more mobile, Fallow Deer for native Roe Deer. Mechanisms driving Roe Deer fertility may include interspecific behavioral interference or stress–resource depletion is considered less likely because Roe Deer fertility was independent of body mass. Findings emphasize the importance of ensuring appropriate management strategies for controlling invasive species. [ABSTRACT FROM AUTHOR]

During the breeding season, hundreds of anurans agglomerate at spawning sites, where a diversity of social contexts arise. In this scenario, anurans may alter their vocal repertoire according to the immediate social context, to overcome intraspecific competition. To evaluate the acoustic response of Boana goiana to successive interactions with a conspecific competitor, the present study was based on comparing the repetition rates of advertisement and aggressive calls of B. goiana focal males exposure to repeated artificial advertisement calls in 10 playback sessions. We observed that B. goiana males altered their acoustic behaviour in response to the simulated arrival of a new competitor. Males emitted less advertisement calls and more aggressive calls with the arrival of the competitors. Temperature and body condition were not important predictors of continuity of males in the experiment or the call repetition rates in the pre-playback session. However, the body condition influenced the total delta advertisement calls (differences in the call rate emission between end and the beginning of the experiment), indicating that higher values of body conditions allow males to show smaller reductions in the emission of advertisement calls over time in the presence of a competitor. [ABSTRACT FROM AUTHOR]

To explore the effects of different water levels on competition of submerged plants, we selected the canopy submerged plant Potamogeton malaianus Miq. and the erect submerged plant Hydrilla verticillata (L. f.) Royle as study materials. Four water level gradients (25, 50, 75, 100 cm) were chosen to simulate the hydrological environment of shallow depressions in the main distribution area of submerged plants in the field. The competition between P. malaianus and H. verticillata under different water levels was investigated by measuring plant height, root length, stem thickness, number of leaves, nodal thrift, nodal spacing, above—ground biomass, below—ground biomass, and canopy whole—plant biomass. The results show that P. malaianus and H. verticillata increased in height as the water level rose. In most treatments, above—ground parts grew better than below ground parts. In the 25 cm water level, relative yields (RYs) of the above—and below—ground parts, and whole plant of P. malaianus displayed different patterns. At the water level of 25 cm, the RY values of the above—ground part, below—ground part, and whole plant of P. malaianus were greater than 1. At the low water level of 25 cm, all treatments had relative yield total (RYT) values greater than 1, and at 50 cm water level, the RYT value of P4H8 was greater than 1. RYT was less than 1 at both 75 and 100 cm at 75 and 100 cm water levels, the growth of each species was limited by the other species. In low water level environments, submerged plants switch from a competitive relationship to a facilitative relationship as the water level decreases (stress increases). [ABSTRACT FROM AUTHOR]

The occurrence of more than one embryo per seed (polyembryony) is common among angiosperms; however, there are gaps in the knowledge of its effects on the early stages of plant development. In this context, we study the effects of polyembryony and intraspecific variability in gemellar competition during the seed–seedling transition in Neotropical Handroanthus chrysotricus (Bignoniaceae). We used seeds from five cultivated trees in an urban environment inserted in a biodiversity hotspot (Cerrado). Embryo mass, seed germination, seedling emergence and seedling morphometry were evaluated. We did not find intraspecific variability in seed germination, seedling emergence or the mean number of embryos and seedlings per seed. On the other hand, intraspecific variability was observed during the transition from embryo to seedling. When only one seedling emerged from a seed, the seed–seedling transition was more asynchronous than when more seedlings emerged from one seed (with higher uncertainty and a longer time to emergence of the last seedling). The mass of embryos and seedlings decreased with the increase in the number of embryos in a seed, reinforcing the occurrence of gemellar competition. However, the total mass of embryos per seed was similar. The increase in seedlings per seed also decreased the morphometric measurements of each one. A positive morphometric aspect of the emergence of two seedlings per seed was that they had the highest total seedling mass, evidencing the positive Allee effect. Polyembryony had both positive and negative effects on seed germination and seedling morphology in the species, which helps to understand how this phenomenon acts on seed biology and plant establishment.

Abstract Marine microorganisms have the potential to disperse widely with few obvious barriers to gene flow. However, among microalgae, several studies have demonstrated that species can be highly genetically structured with limited gene flow among populations, despite hydrographic connectivity. Ecological differentiation and local adaptation have been suggested as drivers of such population structure. Here we tested whether multiple strains from two genetically distinct Baltic Sea populations of the diatom Skeletonema marinoi showed evidence of local adaptation to their local environments: the estuarine Bothnian Sea and the marine Kattegat Sea. We performed reciprocal transplants of multiple strains between culture media based on water from the respective environments, and we also allowed competition between strains of estuarine and marine origin in both salinities. When grown alone, both marine and estuarine strains performed best in the high‐salinity environment, and estuarine strains always grew faster than marine strains. This result suggests local adaptation through countergradient selection, that is, genetic effects counteract environmental effects. However, the higher growth rate of the estuarine strains appears to have a cost in the marine environment and when strains were allowed to compete, marine strains performed better than estuarine strains in the marine environment. Thus, other traits are likely to also affect fitness. We provide evidence that tolerance to pH could be involved and that estuarine strains that are adapted to a more fluctuating pH continue growing at higher pH than marine strains.