Natural history and ecology of foraging of the Camponotus crassus Mayr, 1862 (Hymenoptera: Formicidae)

Emerging Trends in Ant-Pollinator Conflict in Extrafloral Nectary-Bearing Plants

The net outcomes of mutualisms are mediated by the trade-offs between the costs and benefits provided by both partners. Our review proposes the existence of a trade-off in ant protection mutualisms between the benefits generated by the ants' protection against the attack of herbivores and the losses caused by the disruption of pollination processes, which are commonly not quantified. This trade-off has important implications for understanding the evolution of extrafloral nectaries (EFNs), an adaptation that has repeatedly evolved throughout the flowering plant clade. We propose that the outcome of this trade-off is contingent on the specific traits of the organisms involved. We provide evidence that the protective mutualisms between ants and plants mediated by EFNs have optimal protective ant partners, represented by the optimum point of the balance between positive effects on plant protection and negative effects on pollination process. Our review also provides important details about a potential synergism of EFN functionality; that is, these structures can attract ants to protect against herbivores and/or distract them from flowers so as not to disrupt pollination processes. Finally, we argue that generalizations regarding how ants impact plants should be made with caution since ants' effects on plants vary with the identity of the ant species in their overall net outcome.

Chemical Camouflage Induced by Diet in a Pest Treehopper on Host Plants

Ants patrol foliage and exert a strong selective pressure on herbivorous insects, being their primary predators. As ants are chemically oriented, some organisms that interact with them (myrmecophiles) use chemical strategies mediated by their cuticular hydrocarbons (CHCs) to deal with ants. Thus, a better understanding of the ecology and evolution of the mutualistic interactions between myrmecophiles and ants depends on the accurate recognition of these chemical strategies. Few studies have examined whether treehoppers may use an additional strategy called chemical camouflage to reduce ant aggression, and none considered highly polyphagous pest insects. We analyzed whether the chemical similarity of the CHC profiles of three host plants from three plant families (Fabaceae, Malvaceae, and Moraceae) and the facultative myrmecophilous honeydew-producing treehopper Aetalion reticulatum (Hemiptera: Aetalionidae), a pest of citrus plants, may play a role as a proximate mechanism serving as a protection against ant attacks on plants. We found a high similarity (>80%) between the CHCs of the treehoppers and two of their host plants. The treehoppers acquire CHCs through their diet, and the chemical similarity varies according to host plant. Chemical camouflage on host plants plays a role in the interaction of treehoppers with their ant mutualistic partners.

Context-Dependent Ant-Pollinator Mutualism Impacts Fruit Set in a Hummingbird-Pollinated Plant

Context-dependence in mutualisms is a fundamental aspect of ecological interactions. Within plant-ant mutualisms, particularly in terms of biotic protection and pollination, research has predominantly focused on elucidating the benefits while largely overlooking potential costs. This notable gap underscores the need for investigations into the drawbacks and trade-offs associated with such mutualistic relationships. Here, we evaluated the role of pericarpial nectaries (PNs) in shaping the dynamics of ant-pollinator mutualisms. Specifically, we investigated whether ants visiting the PN of Palicourea rigida (Rubiaceae) could deter hummingbirds and disrupt pollination, ultimately influencing fruit production. Our research involved manipulative experiments and observation of ant-pollinator interactions on P. rigida plants in the Brazilian savannah. We found that visiting ants can deter hummingbirds and/or disrupt pollination in P. rigida, directly influencing fruit set. However, these results are species-specific. The presence of very aggressive, large predatory ants, such as E. tuberculatum, had a negative impact on hummingbird behavior, whereas aggressive mid-sized ants, such as C. crassus, showed no effects. Our study illuminates the multifaceted aspects of ant-plant mutualisms and underscores the importance of evaluating costs and unexpected outcomes within these ecological relationships.

Extrafloral Nectary-Bearing Plants Recover Ant Association Benefits Faster and More Effectively after Frost-Fire Events Than Frost

The Cerrado confronts threats such as fire and frost due to natural or human-induced factors. These disturbances trigger attribute changes that impact biodiversity. Given escalating climate extremes, understanding the effects of these phenomena on ecological relationships is crucial for biodiversity conservation. To understand how fire and frost affect interactions and influence biological communities in the Cerrado, our study aimed to comprehend the effects of these two disturbances on extrafloral nectar (EFN)-bearing plants (Ouratea spectabilis, Ochnaceae) and their interactions. Our main hypothesis was that plants affected by fire would grow again more quickly than those affected only by frost due to the better adaptation of Cerrado flora to fire. The results showed that fire accelerated the regrowth of O. spectabilis. Regrowth in plants with EFNs attracted ants that proved to be efficient in removing herbivores, significantly reducing foliar herbivory rates in this species, when compared to the species without EFNs, or when ant access was prevented through experimental manipulation. Post-disturbance ant and herbivore populations were low, with frost leading to greater reductions. Ant richness and diversity are higher where frost precedes fire, suggesting that fire restores Cerrado ecological interactions better than frost, with less impact on plants, ants, and herbivores.

Plant species with larger extrafloral nectaries produce better quality nectar when needed and interact with the best ant partners

Few studies have explored the phenotypic plasticity of nectar production on plant attractiveness to ants. Here, we investigate the role of extrafloral nectary (EFN) size on the productivity of extrafloral nectar in three sympatric legume species. We hypothesized that plant species with larger EFNs (i) have higher induced nectar secretion after herbivory events, and (ii) are more likely to interact with more protective (i.e. dominant) ant partners. We target 90 plants of three Chamaecrista species in the field. We estimated EFN size and conducted field experiments to evaluate any differences in nectar traits before and after leaf damage to investigate the phenotypic plasticity of nectar production across species. We conducted multiple censuses of ant species feeding on EFNs over time. Plant species increased nectar descriptors after leaf damage, but in different ways. Supporting our hypothesis, C. duckeana, with the largest EFN size, increased all nectar descriptors, with most intense post-herbivory-induced response, taking its place as the most attractive to ants, including dominant species. EFN size variation was an excellent indicator of nectar productivity across species. The higher control over reward production in plants with larger sized EFNs reflects an induction mechanism under damage that reduces costs and increases the potential benefits of indirect biotic defences.

Temporal variation in the effect of ants on the fitness of myrmecophilic plants: seasonal effect surpasses periodic benefits

Plants provide extrafloral nectar, which is a food resource taken by ants, especially aggressive species that may act as plant guards. To our knowledge, no study has been conducted to concurrently investigate the fluctuation of plant fitness over its whole reproductive season, recording and comparing both short periods (different samplings during the plant's reproductive season) and the season/pooled data (all fruits produced during the reproductive season). Here, by assigning plants to either ant-present or absent treatments, we investigated the influence of the protective foliage-dwelling ant, Camponotus crassus, on the flower bud and fruit production of four extrafloral nectaried plants (Ancistrotropis firmula, Bionia coriacea, Cochlospermum regium, and Peixotoa tomentosa) throughout their annual reproductive season. Periodic samples in the field revealed a large variation in plant reproduction throughout the season; the increases in buds and fruits were not constantly higher in plants with ants, and in fact, plants without ants had more reproductive structures sometimes. Nonetheless, the examination of the pooled data, i.e., cumulative number of flower buds and fruits produced during the reproductive season, revealed the plants with ants produced more flower buds and fruits (e.g., up to two-fold greater in A. firmula) compared to ant-absent treatments. Our results indicate the effects of ants on plant reproduction are not constant over time, but the net benefits to plants with ants are reflected in increased fruit production. Therefore, the investigations of the benefit of ants on plants should consider the whole plant's reproductive season rather than single samplings within plant reproduction period.

What is the influence of agroecological and conventional crops under ant assemblages?

The objective of the study was to compare the richness and diversity of ant assemblages in an agroecological system under peach orchard, conventional system under peach orchard cultivation and native vegetation in rural properties located in a Pampa Biome. The study was conducted in four samplings in 2017: 1st and 09th March (summer); 24th and 31st July (winter); and four samplings in 2018: 23rd and 30th January (summer); 31st July and 07th August (winter). Pitfall traps were used. The assemblages were characterized and compared using richness, number of occurrences of ants, Shannon diversity (H'), equitability, rarefaction analysis and Chao 1. The association of the species with the samples was evaluated by a Principal Component Analysis (PCA). The agroecological system had the highest number of occurrences, while the conventional orchard the lowest number. Richness and abundance were greatest during the summer. The conventional peach orchard obtained the lowest H' for both seasons when compared to the agroecological orchard and native vegetation. The PCA explained 77.40% of the occurrence of ants in the environments and in the seasons. The results found demonstrated that conservationist systems tend to harbor greater wealth and diversity of ant assemblages, as well as occurring in native áreas.

The effects of high-severity fires on the arboreal ant community of a Neotropical savanna

Fire-suppression is of concern in fire-prone ecosystems because it can result in the loss of endemic species. Suppressing fires also causes a build-up of flammable biomass, increasing the risk of severe fires. Using a Before-After, Control-Impacted design, we assessed the consequences of high-severity fires on Neotropical savanna arboreal ant communities. Over a 9-year period, we sampled the ant fauna of the same trees before and after two severe fires that hit a savanna reserve in Brazil and the trees from an unburned savanna site that served as a temporal control. The ant community associated with the unburned trees was relatively stable, with no significant temporal variation in species richness and only a few species changing in abundance over time. In contrast, we found a strong decline in species richness and marked changes in species composition in the burned trees, with some species becoming more prevalent and many becoming rare or locally extinct. The dissimilarity in species richness and composition was significantly smaller between the two pre-fire surveys than between the pre- and post-fire surveys. Fire-induced changes were much more marked among species with strictly arboreal nesting habits, and therefore more susceptible to the direct effects of fire. The decline of some of the ecologically dominant arboreal ant species may be particularly important, as it opens substantial ecological space for cascading community-wide changes. In particular, severe fires appear to disrupt the typical vertical stratification between the arboreal and ground-dwelling faunas, which might lead to homogenization of the overall ant community.

Foraging and Spatial Ecology of a Polydomous Carpenter Ant, Camponotus leydigi (Hymenoptera: Formicidae), in Tropical Cerrado Savanna: A Natural History Account

Carpenter ants (genus Camponotus) are considered to be predominantly omnivorous, mixing several feeding habits that include predation, scavenging of animal matter, and plant-derived resources. Nitrogen acquisition is crucial for the nutritional ecology of ant colonies because growing larvae require sustainable protein provisioning. Here, we investigate the foraging ecology and the spatial nesting structure of the carpenter ant, Camponotus leydigi Forel, in Brazilian cerrado savanna. By marking workers from different nests with distinct colors, we revealed that C. leydigi occupies physically separated but socially connected nests (up to 30 m apart), a phenomenon known as polydomy. Observational data on aboveground internest movements in C. leydigi corroborate cooperative exchanges between nest units and confirm several types of social connections, including internest transfer of liquid and solid food, transport of colony members (brood, workers), movement of solitary workers, and internest recruitment. Polydomous C. leydigi allocate foragers throughout 1,700 m2, feeding mostly on termites and plant-derived exudates. Influx of exudates is threefold higher compared with solid food. Uric acid pellets excreted by lizards comprise 20% of the solid diet in C. leydigi, a rare quantitative assessment of this peculiar type of nitrogen complementation in ants. Based on video recordings, we hypothesize that nest decentralization in C. leydigi may reduce foraging constraints caused by overt interference by the aggressive ant, Ectatomma brunneum Smith, F. (Hymenoptera: Formicidae), which regularly blocks nest entrances. Our field study enhances the importance of natural history data to clarify selective pressures underlying the evolution of particular behavioral patterns (nutritional and nesting habits) in ants.