Competition, cooperation, and parental effects in larval aggregations formed on carrion by communally breeding beetles Necrodes littoralis (Staphylinidae: Silphinae).

Aggregations of juveniles are dominant forms of social life in some insect groups. Larval societies are shaped by competitive and cooperative interactions of the larvae, in parallel with parental effects. Colonies of necrophagous larvae are excellent systems to study these relationships. Necrodes littoralis (Staphylinidae: Silphinae), a carrion beetle that colonizes cadavers of large vertebrates, forms massive juvenile aggregations. By spreading over carrion anal and oral exudates, the beetles form the feeding matrix, in which the heat is produced and by which adults presumably affect the fitness of the larvae. We predict that exploitative competition shapes the behavior of N. littoralis larvae in their aggregations. However, cooperative interactions may also operate in these systems due mainly to the benefits of collective exodigestion. Moreover, indirect parental effects (i.e., formation of the feeding matrix) probably modulate larval interactions within the aggregations. By manipulating parental effects (present/absent) and larval density (0.02-1.9 larvae/g of meat), we found a strong negative group-size effect on fitness components of N. littoralis, in colonies with parental effects over almost the entire density range, and in colonies without parental effects for densities larger than 0.5 larva/g. This was accompanied by positive group-size effects in terms of development time (it shortened with larval density) and thermogenesis (it increased with larval density). A pronounced positive group-size effect on juvenile fitness was found only in colonies without parental effects and only in the low-density range. These results support the hypothesis that larval societies of N. littoralis are shaped by exploitation competition.

Sexual selection and mate limitation shape evolution of species' range limits.

Understanding what processes shape the formation of species' geographic range limits is one central objective linking ecology and evolutionary biology. One potentially key process is sexual selection; yet, theory examining how sexual selection could shape eco-evolutionary dynamics in marginal populations is still lacking. In species with separate sexes, range limits could be shaped by limitations in encountering mates at low densities. Sexual selection could therefore modulate mate limitation and resulting extinction-colonization dynamics at range margins, through evolution of mate encounter ability and/or mate competition traits, and their demographic consequences. We use a spatially explicit eco-genetic model to reveal how different forms of sexual selection can variably affect emerging range limits. Larger ranges emerged when sexual selection acted exclusively on traits increasing mate encounter probability, thus reducing female's mate limitation toward the range margins. In contrast, sexual selection via mate competition narrowed range limits due to increased trait-dependent mortality in males and elevated mate limitation for females. When mate encounter coevolved with mate competition, their combined effects on range limits depended on the mating system (polygyny vs. monogamy). Our results demonstrate that evolution of species' ranges may be importantly shaped by feedbacks between sexual selection and spatial population demography and dynamics.

Counting Nemo: anemonefish Amphiprion ocellaris identify species by number of white bars.

The brilliant colors of coral reef fish have received much research attention. This is well exemplified by anemonefish, which have distinct white bar patterns and inhabit host anemones and defend them as a territory. The 28 described species have between 0 and 3 white bars present, which has been suggested to be important for species recognition. In the present study, we found that Amphiprion ocellaris (a species that displays three white bars) hatched and reared in aquaria, when faced with an intruder fish, attacked their own species more frequently than other species of intruding anemonefish. Additionally, we explicitly tested whether this species could distinguish models with different numbers of bars. For this, 120 individuals of A. ocellaris were presented with four different models (no bars, and 1, 2 and 3 bars) and we compared whether the frequency of aggressive behavior towards the model differed according to the number of bars. The frequency of aggressive behavior toward the 3-bar model was the same as against living A. ocellaris, and was higher than towards any of the other models. We conclude that A. ocellaris use the number of white bars as a cue to identify and attack only competitors that might use the same host. We considered this as an important behavior for efficient host defense.

Does intraspecific competition cause oxidative stress? Influence of biotic and abiotic factors on antioxidant system of an invasive round goby.

Changes in oxidative status represent organismal response to stressful external stimuli. While there is substantial knowledge on the influence of abiotic factors on the antioxidant system of different organisms, the impact of biotic factors remains largely unexplored. The aim of the present study was to evaluate the effect of acute competitive interactions on oxidative stress. Territory-resident and intruder round goby Neogobius melanostomus individuals were experimentally subjected to competition for limited shelter resource in three treatments (lasting 1, 6 and 12 h), and oxidative stress parameters (total antioxidant capacity, catalase activity, reduced glutathione, lipid peroxidation), as well as behaviour (time spent in the shelter, guarding the shelter and aggression) were measured. All tested biochemical parameters reached higher values in the liver than in the muscle tissue. Fish behaviour and antioxidant defence did not show any potential relationships reflecting changes in antioxidant status and aggression. Particularly, there was no difference between resident and intruder fish in oxidative stress parameters. We compared our results to the outcome of our previous studies (similar experimental protocol and species) but with acute heat shock as a stressor instead of competition. The higher temperature was found to be a stronger stressor than the competition, most pronounced in total antioxidant capacity and oxidative damage.

Adult facilitation becomes competition as juvenile soapberry bugs age.

Intraspecific interactions can change from facilitative to competitive depending on the organism's ontogeny. In plant-feeding insects, host plant defenses can be strengthened or weakened by insect feeding and can therefore be important for determining whether two insects feeding on the same plant help or harm each other's fitness. Here, I conducted two experiments looking at the direct effect of a physical seed defense and the role of intraspecific facilitation in reducing the effects of that defense for juveniles of the red-shouldered soapberry bug. I demonstrate that juveniles are severely inhibited by the tough seed coat of their host plant, leading to high mortality early in development. Adults, in contrast, can create holes through which younger individuals could potentially feed. I manipulated whether or not seeds were fed on by adults on two host plant species: a well-defended native host and a poorly defended introduced host. Survival in the first week of development was dramatically improved by prior adult feeding, and this facilitation was stronger on the well-defended host plant. However, the benefits of prior adult feeding ceased after the first week of development and shifted to having a negative effect on survival, development time, and body size. These results indicate that ontogeny is a key factor determining the effects of plant defenses and the strength and direction of intraspecific interactions across multiple host plant species.

Encounters between pairs of unfamiliar dogs in a dog park.

INTRODUCTION: The aim of this study was to explore spontaneous social interactions between dyads of unfamiliar adult dogs. Although intraspecific encounters are frequent events in the life of pet dogs, the factors that might influence encounters, such as sex, dyad composition, reproductive status, age, and state of cohabitation (keeping the dogs singly or in groups), remained unexplored. METHODS: In this study, we assigned unfamiliar, non-aggressive dogs to three types of dyads defined by sex and size. We observed their unrestrained, spontaneous behaviors in an unfamiliar dog park, where only the two dogs, the owners, and experimenter were present. RESULTS: We found that the dogs, on average, spent only 17% of the time (less than 1 min) in proximity. Sex, dyad composition, reproductive status, and age influenced different aspects of the interactions in dyads. Female dogs were more likely to initiate the first contact in their dyad but later approached the partner less frequently, were less likely to move apart, and displayed less scent marking. Following and moving apart were more frequent in male-male interactions. Neutered dogs spent more time following the other dog and sniffed other dogs more frequently. The time companion dogs spent in proximity and number of approaches decreased with age. CONCLUSION: The study provides guidance for dog owners about the outcomes of intraspecific encounters based on the dog's age, sex, and reproductive status, as well as the sex of the interacting partner.

Functional response and multiple predator effects of two generalist predators preying on Tuta absoluta eggs.

BACKROUND: Interactions among invertebrate predators could affect a pest suppression. The hemipteran species Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) are natural enemies of several pests in agroecosystems and coexist in tomato crops in Mediterranean countries. By using the multiplicative risk model (MRM) and the substitutive model, the multiple predator effects (MPEs) on prey suppression were calculated when two individuals of the predators foraged at the same densities on South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), eggs. RESULTS: Egg consumption increased with increasing egg density and the two predators exhibited a type III functional response. Predation rates were strongly affected by prey density. Using the MRM, we found risk reduction at intraspecific treatments at high prey density. Applying the substitutive model, we detect risk enhancement at interspecific treatments at high egg density. CONCLUSIONS: At low prey densities, most of the interactions were independent, whereas at high densities most interactions were not independent and resulted in prey risk reduction, indicating antagonism between the individuals involved. We also showed that N. tenuis is a more competitive predator species for T. absoluta eggs than M. pygmaeus; however, combination of the two predator species will lead to better pest suppression at high T. absoluta population densities. © 2017 Society of Chemical Industry.

Variation in spatial scale of competing polydomous twig-nesting ants in coffee agroecosystems.

Arboreal ants are both highly diverse and ecologically dominant in the tropics. This ecologically important group is particularly useful in ongoing efforts to understand processes that regulate species diversity and coexistence. Our study addresses how polydomy can influence patterns of nest occupation in competing arboreal ants. We examined the spatial structure of nest occupation (nest distance, abundance and density) in three polydomous co-occurring twig-nesting ant species (Pseudomyrmex simplex, P. ejectus and P. PSW-53) by mapping twigs occupied by ants from each species within plots in our study site. We then used two colony structure estimators (intraspecific aggression and cuticular hydrocarbon variation) to determine the relative degree of polydomy for each species. All work was conducted in coffee agroforests in Chiapas, Mexico. Our results revealed that the two species with highest abundance and nest density were also highly polydomous, where both species had either single or multiple non-aggressive colonies occupying nests on a large spatial scale (greater than the hectare level). Our results also indicate that the species with the lowest abundance and density is less polydomous, occupying several overlapping and territorial colonies at the hectare level in which multiple colonies never co-occur on the same host plant. These results contribute evidence that successful coexistence and highly polydomous colony structure may allow ants, through reduced intraspecific aggression, to successfully occupy more nests more densely than ant species that have multiple territorial colonies. Furthermore our study highlights the importance of considering intraspecific interactions when examining community assembly of ants.

Effects of Spatial Patch Arrangement and Scale of Covarying Resources on Growth and Intraspecific Competition of a Clonal Plant.

Spatial heterogeneity in two co-variable resources such as light and water availability is common and can affect the growth of clonal plants. Several studies have tested effects of spatial heterogeneity in the supply of a single resource on competitive interactions of plants, but none has examined those of heterogeneous distribution of two co-variable resources. In a greenhouse experiment, we grew one (without intraspecific competition) or nine isolated ramets (with competition) of a rhizomatous herb Iris japonica under a homogeneous environment and four heterogeneous environments differing in patch arrangement (reciprocal and parallel patchiness of light and soil water) and patch scale (large and small patches of light and water). Intraspecific competition significantly decreased the growth of I. japonica, but at the whole container level there were no significant interaction effects of competition by spatial heterogeneity or significant effect of heterogeneity on competitive intensity. Irrespective of competition, the growth of I. japonica in the high and the low water patches did not differ significantly in the homogeneous treatments, but it was significantly larger in the high than in the low water patches in the heterogeneous treatments with large patches. For the heterogeneous treatments with small patches, the growth of I. japonica was significantly larger in the high than in the low water patches in the presence of competition, but such an effect was not significant in the absence of competition. Furthermore, patch arrangement and patch scale significantly affected competitive intensity at the patch level. Therefore, spatial heterogeneity in light and water supply can alter intraspecific competition at the patch level and such effects depend on patch arrangement and patch scale.

Microhabitat selection in the common lizard: implications of biotic interactions, age, sex, local processes, and model transferability among populations.

Modeling species' habitat requirements are crucial to assess impacts of global change, for conservation efforts and to test mechanisms driving species presence. While the influence of abiotic factors has been widely examined, the importance of biotic factors and biotic interactions, and the potential implications of local processes are not well understood. Testing their importance requires additional knowledge and analyses at local habitat scale. Here, we recorded the locations of species presence at the microhabitat scale and measured abiotic and biotic parameters in three different common lizard (Zootoca vivipara) populations using a standardized sampling protocol. Thereafter, space use models and cross-evaluations among populations were run to infer local processes and estimate the importance of biotic parameters, biotic interactions, sex, and age. Biotic parameters explained more variation than abiotic parameters, and intraspecific interactions significantly predicted the spatial distribution. Significant differences among populations in the relationship between abiotic parameters and lizard distribution, and the greater model transferability within populations than between populations are in line with effects predicted by local adaptation and/or phenotypic plasticity. These results underline the importance of including biotic parameters and biotic interactions in space use models at the population level. There were significant differences in space use between sexes, and between adults and yearlings, the latter showing no association with the measured parameters. Consequently, predictive habitat models at the population level taking into account different sexes and age classes are required to understand a specie's ecological requirements and to allow for precise conservation strategies. Our study therefore stresses that future predictive habitat models at the population level and their transferability should take these parameters into account.

Diet and feeding behavior of the White-naped Jay, Cyanocorax cyanopogon (Wied, 1821) (Aves, Passeriformes, Corvidae) in a disturbed environment in central Brazil / Dieta e comportamento alimentar de Cyanocorax cyanopogon (Wied, 1821) (Aves, Passeriformes, Corvidae) em um ambiente antropizado na região centro-oeste do Brasil

The White-naped Jay Cyanocorax cyanopogon (Wied, 1821) is an omnivorous and opportunistic species, with a multifarious diet. In view of the scarcity of available data in the literature, the aim was to investigate and describe the bird's diet, location of food items, foraging tactics, actual feeding behavior and intraspecific interactions, as a means of defining the items consumed. The study was carried out in a Cerrado area in the Araguaia Campus of the Federal University of Mato Grosso – UFMT, in Pontal do Araguaia, Mato Grosso State, Brazil, from August to December, 2006, and from April to October, 2010. All the feeding events were recorded through 136 hours of animal focal sampling, whereby it was shown that these birds predominantly consume animal nutrients, replenished by vegetable items and human food-waste. Arthropods were predominant in the diet, with ants as the most abundant and frequent item. The fruits, flowers and seeds of eleven plant species were also consumed. Food-waste, representing about 1/10 of the total, was constantly consumed even when other food sources were available. Although active among the various strata, foraging is mainly on the ground. In the event of food-scarcity, the strategy employed is the hierarchical deployment of the members of various-sized groups, with the avoidance of direct competition. This versatility during all seasons, confirms total adaptation to the anthropic environment surrounded by native habitats that characterized the study site.

Cyanocorax cyanopogon (Wied, 1821) é uma espécie onívora e oportunista, que se alimenta de diferentes itens alimentares. Como há poucos relatos na literatura sobre sua alimentação, este estudo visou descrever os itens alimentares consumidos, o local de captura do alimento, as táticas de forrageamento, o comportamento alimentar e as interações intraespecíficas de C. cyanopogon. O estudo foi realizado em uma área de Cerrado do Campus Universitário do Araguaia, Universidade Federal de Mato Grosso, em Pontal do Araguaia/MT, de agosto a dezembro de 2006 e de abril a outubro de 2010. Por meio da amostragem animal focal foram registrados todos os eventos alimentares, num total de 136 h de observações. Os resultados demonstraram que C. cyanopogon consome predominantemente alimentos de origem animal, seguidos pelos de origem vegetal e por resíduos alimentares. Os artrópodes foram predominantes em sua dieta e as formigas foram os itens animais mais abundantes e frequentes. Frutos, flores e sementes de onze espécies de plantas também foram consumidos. Resíduos alimentares representaram cerca de um décimo dos itens consumidos, sendo ingeridos mesmo em períodos de disponibilidade de outras fontes alimentares. C. cyanopogon é forrageadora ativa e utiliza diferentes estratos para a captura do alimento, com maior utilização do solo. Forrageia sempre em grupos de tamanhos variados e apresenta um sistema hierárquico para o consumo de itens menos abundantes, sem haver competição direta pelo alimento. Por consumirem diferentes tipos de alimentos e em todas as estações do ano, conclui-se que C. cyanopogon está totalmente adaptada ao ambiente ocupado pelo ser humano, mas circundado por vegetação nativa, característica do local de estudo.

Plant clonal morphologies and spatial patterns as self-organized responses to resource-limited environments.

We propose here to interpret and model peculiar plant morphologies (cushions and tussocks) observed in the Andean Altiplano as localized structures. Such structures resulting in a patchy, aperiodic aspect of the vegetation cover are hypothesized to self-organize thanks to the interplay between facilitation and competition processes occurring at the scale of basic plant components biologically referred to as 'ramets'. (Ramets are often of clonal origin.) To verify this interpretation, we applied a simple, fairly generic model (one integro-differential equation) emphasizing via Gaussian kernels non-local facilitative and competitive feedbacks of the vegetation biomass density on its own dynamics. We show that under realistic assumptions and parameter values relating to ramet scale, the model can reproduce some macroscopic features of the observed systems of patches and predict values for the inter-patch distance that match the distances encountered in the reference area (Sajama National Park in Bolivia). Prediction of the model can be confronted in the future with data on vegetation patterns along environmental gradients so as to anticipate the possible effect of global change on those vegetation systems experiencing constraining environmental conditions.

Bacteriocin-mediated interactions within and between coexisting species.

Bacteriocins are bacteriocidal toxins released by almost all bacteria. They are thought to have a narrow range of killing, but as bacteriocin-mediated interactions have been rarely studied at biologically relevant scales, whether this narrow range of action falls mostly within or mostly between coexisting species in natural communities is an open question with important ecological and evolutionary implications. In a previous study, we systematically sampled Xenorhabdus bacteria along a hillside and found evidence for genotypic variability and bacteriocin-mediated interactions within Xenorhabdus bovienii and X. koppenhoeferi colonies that were collected only a few meters apart. In contrast, colonies that were isolated from the same soil sample were always genetically similar and showed no inhibitions. Here, we conducted pairwise growth-inhibition assays within and between seven X. bovienii and five X. koppenhoeferi colonies that were isolated from different soil samples; all seven X. bovienii colonies and at least three of the X. koppenhoeferi have been distinguished as distinct genotypes based on coarse-grain genomic markers. We found signatures for both conspecific and heterospecific bacteriocin inhibitions in this natural community of Xenorhabdus bacteria, but intraspecific inhibitions were significantly more common than interspecific inhibitions. These results suggest that bacteriocins have a major role in intraspecific competition in nature, but also suggest that bacterocins are important in mediating interspecific interactions among coexisting species in natural communities.

Population-level specificity in the plant-mycorrhizae association alters intraspecific interactions among neighboring plants.

Although variation in the effectiveness of the plant-mycorrhizal association has been demonstrated among plant species and among crop cultivars, the level of specificity of the plant-mycorrhizal association in natural populations and, in particular, its effect on intraspecific plant interactions have not been explored. To examine the influence of the specificity of the plant-mycorrhizal association on intraspecific interactions in Allium vineale, we surrounded target plants with either genetically identical neighbors, neighbors from the same population, or neighbors from a different population, and planted them in pots either with or without a soil fungi community. Overall, the presence of a soil fungal community was beneficial for plant growth, and thus the soil fungal community effects in this system are dominated by the mutualistic effect of mycorrhizae. In addition, both the target plant and neighbor plants had a relatively greater benefit from the mycorrhizal association if the neighbors were genetically identical or from the same population than if the neighbors came from a different population. Thus, there is specificity in the interaction between A. vineale plants and the soil fungal community at the population level, and this specificity favors intraspecific interactions among plants from the same population. In addition, in the presence of the soil fungal community, the variance in plant size within a pot was greater among neighbors from a different population. Therefore the growth advantage for plants growing with neighbors from the same population was not due to pre-emption of resources by individual plants. This finding provides indirect evidence to support the hypothesis that plants from the same population were able to share a more efficient hyphal network.