Integrating animal personality into insect population and community ecology

Top-down effects of intraspeciflic predator behavioral variation

Among-individual variation in predator traits is ubiquitous in nature. However, variation among populations in this trait variation has been seldom considered in trophic dynamics. This has left unexplored (a) to what degree does among-individual variation in predator traits regulate prey populations and (b) to what degree do these effects vary spatially. We address these questions by examining how predator among-individual variation in functional traits shapes communities across habitats of varying structural complexity, in field conditions. We manipulated Chinese mantis (Tenodera sinensis) density (six or twelve individuals) and behavioral trait variability (activity level by movement on an open field) in experimental patches of old fields with varying habitat complexity (density of plant material). Then, we quantified their impacts on lower trophic levels, specifically prey (arthropods > 4 mm) and plant biomass. Predator behavioral variability only altered prey biomass in structurally complex plots, and this effect depended on mantis density. In the plots with the highest habitat complexity and mantis density, behaviorally variable groups decreased prey biomass by 40.3%. In complex plots with low mantis densities, low levels of behavioral variability decreased prey biomass by 32.2%. Behavioral variability and low habitat complexity also changed prey community composition, namely by increasing ant biomass by 881%. Our results demonstrate that among-individual trait variation can shape species-rich prey communities. Moreover, these effects depend on both predator density and habitat complexity. Incorporating this important facet of ecological diversity revealed normally unnoticed effects of functional traits on the structure and function of food webs.

Transgenerational plasticity of exploratory behavior and a hidden cost of mismatched risk environments between parental sexes

We require a better understanding of the relative contribution of different modes of non-genetic inheritance in behavioral trait development. Thus, we investigate variation in exploratory behavior, which is ecologically relevant and a target of selection. The metabolic hypothesis predicts exploratory behavior to be size-dependent across taxa. This size-dependency is cancelled out under high perceived risk, allowing us to determine the transgenerationally integrated estimated level of risk. Using fathead minnows Pimephales promelas, we manipulated perceived risk in mothers, fathers, caring males and offspring through continuous exposure to either conspecific alarm cues or to a control water treatment. In 1000 four-month old offspring, we determined body sizes and exploratory behavior. Perceived high risk in mothers, followed by personal risk, was most effective in eliminating size-dependent behavior whereas effects of paternal risk on offspring behavioral development were substantially weaker. When maternal risk is high, environmental mismatches between parents prevented offspring from responding appropriately to personal high risk. The environment of the caring male also impacted offspring behavior to a greater extent than that of its genetic parents. Our study highlights the high relative importance of maternal, personal and caring male risk environments and showcases potential costs of an environmental mismatch between parental sexes.

Sex-specific life-history strategies among immature jumping spiders: Differences in body parameters and behavior

Selection forces often generate sex-specific differences in various traits closely related to fitness. While in adult spiders (Araneae), sexes often differ in coloration, body size, antipredator, or foraging behavior, such sex-related differences are less pronounced among immatures. However, sex-specific life-history strategies may also be adaptive for immatures. Thus, we hypothesized that among spiders, immature individuals show different life-history strategies that are expressed as sex-specific differences in body parameters and behavioral features, and also in their relationships. We used immature individuals of a protandrous jumping spider, Carrhotus xanthogramma, and examined sex-related differences. The results showed that males have higher mass and larger prosoma than females. Males were more active and more risk tolerant than females. Male activity increased with time, and larger males tended to capture the prey faster than small ones, while females showed no such patterns. However, females reacted to the threatening abiotic stimuli more with the increasing number of test sessions. In both males and females, individuals with better body conditions tended to be more risk averse. Spiders showed no sex-specific differences in interindividual behavioral consistency and in intraindividual behavioral variation in the measured behavioral traits. Finally, we also found evidence for behavioral syndromes (i.e., correlation between different behaviors), where in males, only the activity correlated with the risk-taking behavior, but in females, all the measured behavioral traits were involved. The present study demonstrates that C. xanthogramma sexes follow different life-history strategies even before attaining maturity.

Behavioural Repeatability and Behavioural Syndrome in the Dung Beetle Copris umbilicatus (Coleoptera, Scarabaeidae)

Although personality studies have primarily focused on vertebrates, the evidence showing invertebrates to be capable of displaying personalities has been steadily growing in recent years. In this study, we investigated the behavioural repeatability (repetition of a behaviour over time) and behavioural syndromes (a set of correlated behaviours) in Copris umbilicatus, which is a dung beetle species showing complex sub-social behaviour. We analysed three behaviours (activity, thanatosis and distress call emission) by measuring seven distinct behavioural traits (i.e., three activity-, one thanatosis- and three distress call-related traits). We found moderate to high levels of individual repeatability in all behavioural traits considered. The duration of thanatosis was inversely correlated with two activity traits, hinting a behavioural syndrome for thanatosis and activity, with bolder individuals exhibiting shorter thanatosis and higher locomotor activity in contrast with fearful individuals, which display longer thanatosis and poor locomotor activity. No relationships were found between the behavioural traits and body size or sex. Results of the principal component analysis (PCA) suggested personality differences among individuals. Dung beetles provide an impressive variety of ecosystem services. Since the provision of these services may depend on the personalities represented in local populations and communities, studies on the ecology of personality in dung beetles should be encouraged in future research.

Maternal exposure to bisphenol S induces neuropeptide signaling dysfunction and oxidative stress in the brain, and abnormal social behaviors in zebrafish (Danio rerio) offspring

Recent studies show that bisphenol S (BPS) induces multiple adverse effects in exposed organisms; however, the maternal effects of BPS exposure remain poorly understood. Here, we expose adult female zebrafish to environmentally relevant concentrations of BPS (0, 1, 10, 30 μg/L) and 1 μg/L of 17-β-estradiol (E2) as a positive control for 60 days. Females were then paired with BPS-unexposed males and their offspring were raised in control water for 6 months. Maternal exposure to BPS was found to alter social behavior and anxiety response in a dose-specific manner in male offspring. Group preferences and social cohesion were significantly reduced by maternal exposure to 1 and 10 μg/L BPS, respectively. Additionally, maternal exposure to 1 and 30 μg/L BPS and E2 decreased offspring stress responses during the novel tank test. The impaired social behavior was associated with elevated arginine-vasotocin (AVT) level as well as with the altered expression of genes involved in AVT signaling pathway (AVT, avpr1aa) and enzymatic antioxidant genes (cat and Mn-sod) in the brain. Collectively, these results suggest that maternal exposure to environmentally relevant concentrations of BPS alters social behavior in zebrafish offspring, which is likely mediated by oxidative stress and disruption of neuropeptide signaling pathways in the brain.

Collective motion as a distinct behavioral state of the individual

The collective motion of swarms depends on adaptations at the individual level. We explored these and their effects on swarm formation and maintenance in locusts. The walking kinematics of individual insects were monitored under laboratory settings, before, as well as during collective motion in a group, and again after separation from the group. It was found that taking part in collective motion induced in the individual unique behavioral kinematics, suggesting the existence of a distinct behavioral mode that we term a "collective-motion-state." This state, characterized by behavioral adaptation to the social context, is long lasting, not induced by crowding per se, but only by experiencing collective motion. Utilizing computational models, we show that this adaptability increases the robustness of the swarm. Overall, our findings suggest that collective motion is not only an emergent property of the group but also depends on a behavioral mode, rooted in endogenous mechanisms of the individual.

Beyond spider personality: The relationships between behavioral, physiological, and environmental factors

Spiders are useful models for testing different hypotheses and methodologies relating to animal personality and behavioral syndromes because they show a range of behavioral types and unique physiological traits (e.g., silk and venom) that are not observed in many other animals. These characteristics allow for a unique understanding of how physiology, behavioral plasticity, and personality interact across different contexts to affect spider's individual fitness and survival. However, the relative effect of extrinsic factors on physiological traits (silk, venom, and neurohormones) that play an important role in spider survival, and which may impact personality, has received less attention. The goal of this review is to explore how the environment, experience, ontogeny, and physiology interact to affect spider personality types across different contexts. We highlight physiological traits, such as neurohormones, and unique spider biochemical weapons, namely silks and venoms, to explore how the use of these traits might, or might not, be constrained or limited by particular behavioral types. We argue that, to develop a comprehensive understanding of the flexibility and persistence of specific behavioral types in spiders, it is necessary to incorporate these underlying mechanisms into a synthesized whole, alongside other extrinsic and intrinsic factors.

The impact of temperature on the life cycle of Gasterophilus pecorum in northwest China

Background

The departure of the mature larvae of the horse stomach bot fly from the host indicates the beginning of a new infection period. Gasterophilus pecorum is the dominant bot fly species in the desert steppe of the Kalamaili Nature Reserve (KNR) of northwest China as a result of its particular biological characteristics. The population dynamics of G. pecorum were studied to elucidate the population development of this species in the arid desert steppe.

Methods

Larvae in the freshly excreted feces of tracked Przewalski’s horses (Equus przewalskii) were collected and recorded. The larval pupation experiments were carried out under natural conditions.

Results

There was a positive correlation between the survival rate and the number of larvae expelled (r = 0.630, p < 0.01); the correlation indicated that the species had characteristic peaks of occurrence. The main periods during which mature larvae were expelled in the feces were from early April to early May (peak I) and from mid-August to early September (peak II); the larval population curve showed a sudden increase and gradual decrease at both peaks. Under the higher temperatures of peak II, the adults developing from the larvae had a higher survival rate, higher pupation rate, higher emergence rate and shorter eclosion period than those developing from peak I larvae. Although G. pecorum has only one generation per year, its occurrence peaked twice annually, i.e. the studied population has a bimodal distribution, which doubles parasitic pressure on the local host. This phenomenon is very rarely recorded in studies on insect life history, and especially in those on parasite epidemiology.

Conclusion

The period during which G. pecorum larvae are naturally expelled from the host exceeds 7 months in KNR, which indicates that there is potentially a long period during which hosts can become infected with this parasite. The phenomenon of two annual peaks of larvae expelled in feces is important as it provides one explanation for the high rate of equine myiasis in KNR.

Does resource-mediated stress affect colony personality in leaf-cutting ants?

BACKGROUND

Animal personality refers to behavioral consistency and propensity. In social insects, little is known about the interplay between colony personality and colony foraging. This study aimed to assess personality traits among colonies of the leaf-cutting ants Acromyrmex subterraneus subterraneus and Acromyrmex subterraneus molestans and examine their behavioral consistency when provided with a toxic substrate, nasturtium leaves [Tropaeolum majus L. (Tropaeolaceae)], with potential as a management tool against these pest species. The association between colony behavioral traits and fungus garden growth was also examined, and thus the efficacy of the colony suppression.

RESULTS

Behavioral variation was higher between colonies than between subspecies. Behavioral traits were correlated before and after exposure to resource-mediated stress in both subspecies, indicating the existence of behavioral syndrome. The dimensions that contributed most to colony personality (activity, aggressiveness, and boldness) are directly related to colony resource searching and foraging. However, these dimensions diverged in their contribution before and after exposure to nasturtium. Colony activity was the major determinant of fungus garden growth, which is probably a consequence of its relationship with foraging behaviors and maintenance of the fungus garden.

CONCLUSION

As the personality of a colony is unequally defined by its constituent castes, the relationship and network of interactions are determinants of foraging behaviors with relevant consequences for colony suppression using toxic foraging substrates that impair these relationships and interactions, as nasturtium leaves do. Therefore, it is plausible to say that resource-mediated stress affects colonies personality exhibiting control potential against these species.

Species-habitat networks elucidate landscape effects on habitat specialisation of natural enemies and pollinators

Measuring habitat specialisation is pivotal for predicting species extinctions and for understanding consequences on ecosystem functioning. Here, we sampled pollinator and natural enemy communities in all major habitat types occurring across multiple agricultural landscapes and used species-habitat networks to determine how habitat specialisation changed along gradients in landscape composition and configuration. Although it is well known that landscape simplification often causes the replacement of specialists with generalists, our study provided evidence for intraspecific variation in habitat specialisation, highlighting how a large number of arthropod species adapted their way of selecting habitat resources depending on the landscape structure. Groups with higher diet specialisation and limited foraging flexibility appeared to have a reduced ability to respond to landscape changes, indicating that some arthropod taxa are better able than others to adapt to an increasingly broad set of resources and persist in highly impacted landscapes.

An individual's propensity to disperse is dependent on the behavioral type of its peers but not its own behavioral type

Intraspecific differences in the dispersal propensity of animals have been linked to interindividual variation in inherent tendencies (i.e., personality or behavioral type) that influence multiple aspects of an individual's behavior. Studies linking dispersal propensity and personality often (1) focus on defining behavioral tendencies with a single behavioral trait rather than multiple, (2) do not recognize that invertebrates may have behavioral tendencies that influence dispersal, and (3) do not consider how the behavioral type of other individuals affects the dispersal propensity of an individual. We documented multiple foraging behaviors of an aquatic predatory insect (Notonecta irrorata) and found that Notonecta individuals differ in their inherent behavioral tendency (i.e., degree of boldness); all foraging behaviors were correlated such that riskier behaviors were exhibited by the same individuals. We conducted an experiment in which we varied which behavioral types of Notonecta were placed in outdoor pools (passive, bold or both types present) and quantified how long it took for individuals to disperse. Passive and bold individuals had a similar propensity to disperse but the dispersal propensity of each behavioral type was influenced by the behavioral type of other conspecifics present in the pool. Our work reveals that (1) invertebrates have inherent behavioral tendencies that vary among individuals but these tendencies do not necessarily impact all of the behavior displayed by the individual (i.e., impact foraging but not dispersal) and (2) the inherent behavioral tendency of other individuals with which an animal co-occurs can affect habitat patch dynamics such as predation, competition, or colonization.

Moving On from the Insect Apocalypse Narrative: Engaging with Evidence-Based Insect Conservation

Recent studies showing temporal changes in local and regional insect populations received exaggerated global media coverage. Confusing and inaccurate science communication on this important issue could have counterproductive effects on public support for insect conservation. The insect apocalypse narrative is fuelled by a limited number of studies that are restricted geographically (predominantly the United Kingdom, Europe, the United States) and taxonomically (predominantly some bees, macrolepidoptera, and ground beetles). Biases in sampling and analytical methods (e.g., categorical versus continuous time series, different diversity metrics) limit the relevance of these studies as evidence of generalized global insect decline. Rather, the value of this research lies in highlighting important areas for priority investment. We summarize research, communication, and policy priorities for evidence-based insect conservation, including key areas of knowledge to increase understanding of insect population dynamics. Importantly, we advocate for a balanced perspective in science communication to better serve both public and scientific interests.

Trait-based ecology of terrestrial arthropods

In focusing on how organisms' generalizable functional properties (traits) interact mechanistically with environments across spatial scales and levels of biological organization, trait-based approaches provide a powerful framework for attaining synthesis, generality and prediction. Trait-based research has considerably improved understanding of the assembly, structure and functioning of plant communities. Further advances in ecology may be achieved by exploring the trait-environment relationships of non-sessile, heterotrophic organisms such as terrestrial arthropods, which are geographically ubiquitous, ecologically diverse, and often important functional components of ecosystems. Trait-based studies and trait databases have recently been compiled for groups such as ants, bees, beetles, butterflies, spiders and many others; however, the explicit justification, conceptual framework, and primary-evidence base for the burgeoning field of 'terrestrial arthropod trait-based ecology' have not been well established. Consequently, there is some confusion over the scope and relevance of this field, as well as a tendency for studies to overlook important assumptions of the trait-based approach. Here we aim to provide a broad and accessible overview of the trait-based ecology of terrestrial arthropods. We first define and illustrate foundational concepts in trait-based ecology with respect to terrestrial arthropods, and justify the application of trait-based approaches to the study of their ecology. Next, we review studies in community ecology where trait-based approaches have been used to elucidate how assembly processes for terrestrial arthropod communities are influenced by niche filtering along environmental gradients (e.g. climatic, structural, and land-use gradients) and by abiotic and biotic disturbances (e.g. fire, floods, and biological invasions). We also review studies in ecosystem ecology where trait-based approaches have been used to investigate biodiversity-ecosystem function relationships: how the functional diversity of arthropod communities relates to a host of ecosystem functions and services that they mediate, such as decomposition, pollination and predation. We then suggest how future work can address fundamental assumptions and limitations by investigating trait functionality and the effects of intraspecific variation, assessing the potential for sampling methods to bias the traits and trait values observed, and enhancing the quality and consolidation of trait information in databases. A roadmap to guide observational trait-based studies is also presented. Lastly, we highlight new areas where trait-based studies on terrestrial arthropods are well positioned to advance ecological understanding and application. These include examining the roles of competitive, non-competitive and (multi-)trophic interactions in shaping coexistence, and macro-scaling trait-environment relationships to explain and predict patterns in biodiversity and ecosystem functions across space and time. We hope this review will spur and guide future applications of the trait-based framework to advance ecological insights from the most diverse eukaryotic organisms on Earth.

Intra- versus intergroup variance in collective behavior

Animal collective motion arises from the intricate interactions between the natural variability among individuals, and the homogenizing effect of the group, working to generate synchronization and maintain coherence. Here, these interactions were studied using marching locust nymphs under controlled laboratory settings. A novel experimental approach compared single animals, small groups, and virtual groups composed of randomly shuffled real members. We found that the locust groups developed unique, group-specific behavioral characteristics, reflected in large intergroup and small intragroup variance (compared with the shuffled groups). Behavioral features that differed between single animals and groups, but not between group types, were classified as essential for swarm formation. Comparison with Markov chain models showed that individual tendencies and the interaction network among animals dictate the group characteristics. Deciphering the bidirectional interactions between individual and group properties is essential for understanding the swarm phenomenon and predicting large-scale swarm behaviors.

Description of a personality syndrome in a common and invasive ground beetle (Coleoptera: Carabidae)

Animal personality, defined as consistent differences among individuals in their behaviour, is being increasingly studied as it might lead to a new understanding of the evolution of behaviours. Despite a clear interest in studying personality in a wide range of taxa for comparative analyses, studies on invertebrates are still scarce. Here, we investigated the personality of a ground beetle, Nebria brevicollis, which is widespread in Europe and invasive in North America. We measured seven behavioural traits from an array of three different tests: (i) activity and exploration related traits; (ii) reaction to a threat, and (iii) phototaxis. The repeatability was tested by measuring all behaviours twice, on different days. All behavioural traits were consistent through time, highlighting the presence of personality in the beetle. In addition, we analysed the relationship between the different traits and highlighted two clusters of behaviours (behavioural syndrome), one grouping activity, exploration and boldness traits, and a second one consisting of responses to a threat. This study is the first to our knowledge to provide evidence for personality dimensions within the vast group of the Carabidae. It also constitutes a preliminary step in the experimental investigation of the importance of animal personality in invasive species.

Eco-evolutionary feedbacks following changes in spatial connectedness

Humans are drastically changing the spatial configuration of habitats. The associated changes in habitat connectedness impose strong selection on dispersal, and dispersal related traits. Evolutionary responses do, however, strongly feedback on the metapopulation dynamics, by further constraining or improving connectivity and impacting local population and food web dynamics. Because these spatial eco-evolutionary interactions occur at contemporary time scales, unique evidence on its importance is especially emerging in the field of entomology as many insects have short generation times and a huge reproductive potential. We review the ecological feedbacks originating from the evolution of dispersal rate, dispersal syndromes and genetic diversity on metapopulation dynamics and range expansions. We thus close the eco-evolutionary loop for insect and arachnid spatial dynamics.

Polistes metricus queens exhibit personality variation and behavioral syndromes

Consistent differences in behavior between individuals, otherwise known as animal personalities, have become a staple in behavioral ecology due to their ability to explain a wide range of phenomena. Social organisms are especially serviceable to animal personality techniques because they can be used to explore behavioral variation at both the individual and group level. Despite the success of personality research in social organisms generally, and social Hymenoptera in particular, social wasps (Vespidae) have received little to no attention in the personality literature. In the present study, we test Polistes metricus (Vespidae; Polistinae) paper wasp queens for the presence of repeatable variation in, and correlations ("behavioral syndromes") between, several commonly used personality metrics: boldness, aggressiveness, exploration, and activity. Our results indicate that P. metricus queens exhibit personalities for all measured traits and correlations between different behavioral measures. Given that paper wasps have served as a model organism for a wide range of phenomena such as kin selection, dominance hierarchies, mate choice, facial recognition, social parasitism, and chemical recognition, we hope that our results will motivate researchers to explore whether, or to what degree, queen personality is important in their research programs.

Intraspecific variation shapes community-level behavioral responses to urbanization in spiders

Urban areas are an extreme example of human-changed environments, exposing organisms to multiple and strong selection pressures. Adaptive behavioral responses are thought to play a major role in animals' success or failure in such new environments. Approaches based on functional traits have proven especially valuable to understand how species communities respond to environmental gradients. Until recently, they have, however, often ignored the potential consequences of intraspecific trait variation (ITV). When ITV is prevalent, it may highly impact ecological processes and resilience against stressors. This may be especially relevant in animals, in which behavioral traits can be altered very flexibly at the individual level to track environmental changes. We investigated how species turnover and ITV influenced community-level behavioral responses in a set of 62 sites of varying levels of urbanization, using orb web spiders and their webs as models of foraging behavior. ITV alone explained around one-third of the total trait variation observed among communities. Spider web structure changed according to urbanization, in ways that increase the capture efficiency of webs in a context of smaller urban prey. These trait shifts were partly mediated by species turnover, but ITV increased their magnitude, potentially helping to buffer the effects of environmental changes on communities. The importance of ITV varied depending on traits and on the spatial scale at which urbanization was considered. Despite being neglected from community-level analyses in animals, our results highlight the importance of accounting for intraspecific trait variation to fully understand trait responses to (human-induced) environmental changes and their impact on ecosystem functioning.

Exposure to predators reduces collective foraging aggressiveness and eliminates its relationship with colony personality composition

Predation is a ubiquitous threat that often plays a central role in determining community dynamics. Predators can impact prey species by directly consuming them, or indirectly causing prey to modify their behavior. Direct consumption has classically been the focus of research on predator-prey interactions, but substantial evidence now demonstrates that the indirect effects of predators on prey populations are at least as strong as, if not stronger than, direct consumption. Social animals, particularly those that live in confined colonies, rely on coordinated actions that may be vulnerable to the presence of a predator, thus impacting the society's productivity and survival. To examine the effect of predators on the behavior of social animal societies, we observed the collective foraging of social spider colonies (Stegodyphus dumicola) when they interact with dangerous predatory ants either directly, indirectly, or both. We found that when colonies were exposed directly and indirectly to ant cues, they attacked prey with approximately 40-50% fewer spiders, and 40-90% slower than colonies that were not exposed to any predator cues. Furthermore, exposure to predatory ants disassociated the well-documented positive relationship between colony behavioral composition (proportion of bold spiders) and foraging aggressiveness (number of attackers) in S. dumicola, which is vital for colony growth. Thus, the indirect effects of predator presence may limit colony success. These results suggest that enemy presence could compromise the organizational attributes of animal societies.

Body size and the behavioral ecology of insects: linking individuals to ecological communities

The role of body size as a key feature determining the biology and ecology of individual animals, and thus the structure and dynamics of populations, communities, and ecosystems, has long been acknowledged. Body size provides a functional link between individual-level processes such as physiology and behavior, with higher-level ecological processes such as the strength and outcome of trophic interactions, which regulate the flow of energy and nutrients within and across ecosystems. Early ecological work on size in animals focused on vertebrates, and especially mammals. More recent focus on invertebrates, and insects in particular, that spans levels of organization from individual physiology to communities, has greatly expanded and improved our understanding of the role of body size in ecology. Progress has come from theoretical advances, from the production of new, high-resolution empirical data sets, and from enhanced computation and analytical techniques. Recent findings suggest that many of the allometric concepts and principles developed over the last century also apply to insects. But these recent studies also emphasize that while body size plays a crucial role in insect ecology, it is not the entire story, and a fuller understanding must come from an approach that integrates both size and non-size effects. In this review we discuss the core principles of a size-based (allometric) approach in insect ecology, together with the potential of such an approach to connect biological processes and mechanisms across levels of organization from individuals to ecosystems. We identify knowledge gaps, particularly related to size constraints on insect movement and behavior, which can impact the strength and outcome of species interactions (and especially trophic interactions) and thus link individual organisms to communities and ecosystems. Addressing these gaps should facilitate a fuller understanding of insect ecology, with important basic and applied benefits.