Ectatomma Brunneum Research Articles

Land‐use change in the Amazon decreases ant diversity but increases ant‐mediated predation

Abstract Food production in Amazonian traditional societies often occurs through shifting cultivation that uses few pesticides and relies on ecosystem services provided by natural enemies. However, these sustainable agricultural practices are being threatened by increasing livestock and mechanised agriculture. This study aimed to evaluate the effects of the conversion from Amazon Forest to anthropogenic land uses (shifting cultivation and pasture) on α‐ and β‐diversity, functional groups, and ant‐mediated predation. Three types of habitats were sampled: forest (eight sites), shifting cultivation (five sites) and pasture (seven sites). The ant assembly of each site was sampled using pitfall traps in the epigeic and hypogeic strata. Beetle larvae were used to evaluate the predation function. Negative effects on epigeic ants and functional groups were found to be greater in sites where anthropogenic land use was more intensive (pasture) than in those where it was less intensive (shifting cultivation). Furthermore, this change increased the predation of insects in shifting cultivation and pasture compared to that in forest. This increase in insect predation was due to high activity of Ectatomma brunneum Smith, 1858, an environmental indicator for shifting cultivation and pasture. The increase in the number of predations in shifting cultivation and pasture may be beneficial from the perspective of biological pest control. However, this relationship needs to be better understood because the high presence and predatory activity of Ectatomma brunneum in these environments may be one mechanism by which α‐ and β‐diversity decrease through antagonistic interactions and dominance.

Epigeic fauna (with emphasis on ant community) response to land-use change for sugarcane expansion in Brazil

The epigeic fauna, ground surface-dwelling invertebrates that inhabit leaf-litter, acts on multiple soil processes and key ecosystem services and is threatened by global land-use change (LUC). In Brazil, LUC for sugarcane expansion over extensive pasture has been taking place for promoting bioenergy production; however, conventional sugarcane cultivation includes monoculture, periodic soil tillage and agrochemicals may alter the quantity and quality of crop residue inputs, soil habitats and communities of soil fauna. Thus, a field study at three sites in central southern Brazil was conducted to evaluate if the expansion of sugarcane cultivation affects soil epigeic fauna. In each site, we sampled epigeic fauna in areas under LUC from native vegetation to extensive pasture, and from that to sugarcane. The epigeic fauna was collected using pitfall traps and then quantified and classified in taxonomic groups (Order, Class, Family). In addition, as a focal organism group, ants were classified at the species level. Overall, 13 taxonomic groups were identified, in which the Formicidae family was the most abundant group (i.e., 67% of individuals), followed by Diptera (13%), Araneae (5%) and Coleoptera (4%). Land transition from native vegetation to pasture increased fauna abundance by 27% but reduced the diversity of epigeic fauna community by 43%. In contrast, sugarcane expansion over extensive pasture reduced fauna abundance (−22%), did not alter the diversity of the invertebrate community at a broad taxonomic level, but decreased species richness of the dominant taxa (ants) by 55%. Ant individuals were classified into 37 species, allowing to verify that sugarcane cultivation over pastures decreased both the abundance and richness of ants and altered community composition. Ant species Ectatomma brunneum were more sensitive to LUC and, therefore, could be characterized as potential indicators of disturbed environments. We demonstrate that sugarcane expansion over pasturelands reduces the total abundance of the soil epigeic fauna, and that effects on fauna diversity vary from broad to fine taxonomic resolutions. Further studies are needed to evaluate if the declines in fauna abundance and ant species richness impair specific soil functions and soil-related ecosystem services.

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.

Intraspecific variation of cuticular hydrocarbons and apolar compounds in the venom of Ectatomma brunneum

By understanding the intraspecific differences of traits presented by a species, we can gain greater insight into their variable functionality in microevolutionary processes relative to genetic and environmental factors leading to ecological adaptation and speciation. However, few studies have evaluated how intraspecific variation of cuticle hydrocarbons (CHCs) occurs in relation to the apolar part of ant venom. Therefore, this study aimed to evaluate the chemical composition of compounds present in the cuticle and venom of different populations of Ectatomma brunneum ants. To accomplish this, 310 foragers from different populations were collected. Analysis of CHCs and the apolar part of the venom was performed using a gas chromatograph coupled to a mass spectrometer. Our results show that both the composition of CHCs and the apolar part of the venom vary significantly among the different populations. Differences in composition between the two types of compounds correlate with the geographic distance between the populations. In this sense, the greater the distance, the smaller is the gene flow between them. On the other hand, particular environmental conditions, such as temperature, humidity and available resources, leading to changes generated by adaptation, could be responsible for a part of these differences.

Can altered magnetic field affect the foraging behaviour of ants?

Social insects such as ants can use geomagnetic field information in orientation and navigation tasks. However, few studies have assessed the effect of magnetic fields on aspects such as orientation and decision making during foraging of ants. Therefore, the present study aims to test the hypothesis that foragers of different species of ants with different foraging strategies when under effect of applied magnetic field change the patterns of search for resources and recruitment of ants. We used two species with solitary foraging strategy, Ectatomma brunneum and Neoponera inversa, and another with mass recruitment, Pheidole sp. The experiments were performed in field and laboratory conditions. We used some parameters for comparison such as speed, distance and time during foraging in the field and laboratory experiments, under normal and applied magnetic field with the coils on and off. We also performed SQUID magnetometry analysis for all species. The results demonstrate that changes in normal values of magnetic field affect workers behaviour of the three species. Thus, we can conclude that ants under the effect of applied magnetic fields can suffer significant changes in their foraging activities decreasing the flow of workers, increasing the travelled distance from the nest to the resource and back to the nest, in addition to time and distance to fetch the resource and decision-making, in both types of species, those which have mass recruitment, or forage individually, and that the three species are magnetosensitive, being affected by changes of low intensity in the local magnetic field.

Evaluation of Inter and Intraspecific Differences in the Venom Chemical Compositions of Polybia paulista Wasps and Ectatomma brunneum Ants Using FTIR-PAS

Wasps can synthesize chemical compounds called venom whose function is to overcome prey and assist in defense of the colonies. Geographic Parameters such as sex, age, the season of the year, and diet determined the composition of the venom location, genetics, environment. However, studies on the compositional variability of venom are still limited due to the difficulty in obtaining samples and the complexity of these substances. This work describes the use of the Fourier Transform Infrared Photoacoustic Spectroscopy (FTIR-PAS) to investigate inter- and intraspecific variability in the venom chemical composition (VCC) of the social wasp Polybia paulista (Von Ihering 1896) and the ant Ectatomma brunneum (Smith 1858). The results reveal significant differences in VCC among the ant and wasp, even for samples obtained from the same environment. The genetic component, therefore, seemed to be the predominant factor determining the compounds present. The findings also showed that exogenous factors, such as diet, could also be responsible for intraspecific differences, especially in wasps. The FTIR-PAS technique proved to be a reliable way of assessing intra- and interspecific differences in social Hymenoptera VCC.

Dear Enemy Phenomenon in the Ant Ectatomma brunneum (Formicidae: Ectatomminae): Chemical Signals Mediate Intraspecific Agressive Interactions

The integrity of ant colonies depends exclusively on social relationships between their individuals, especially the ability of communication between group members, which is mainly mediated through chemical signals. Another important feature of ant behavior is territory defense, since they need to gather large amounts of food to feed their larvae, males and breeding females. Thereby, ants might display behavioral strategies to defend their territories from intruders. Here we investigated whether Ectatomma brunneum displays the Dear Enemy Phenomenon, what is the relationship between Cuticular Hydrocarbon composition and levels of aggression during their intraspecific interactions and which compounds and/or classes of compounds might be the most important to modulate the level of aggression. To test our hypothesis, we evaluated the levels of aggression through behavioral observations during interactions between 23 pairs of colonies nested in two distinct sites at varied distances. Then, we analyzed the cuticular chemical profile of the individuals involved in the interactions, and compared these results with the levels of aggression displayed between colonies tested. The results allow us to confirm our hypothesis that the DEP occurs in E. brunneum. The higher tolerance between closer colonies can be explained due to their kinship level in addition to sharing the same microhabitats. The results also showed there are significant differences in CHCs profiles, especially between colonies nested at relatively greater distances, and it is likely that differences in content of some branched alkanes are the most important to establish these differences and, therefore, the levels of aggression during the interactions.

Effect of temperature on survival and cuticular composition of three different ant species

Climatic factors, such as temperature variation, interfere with the survival of insects. To respond to these variations, insects have some specific characteristics. These include water content of the body, thickness of the lipid layer, as well as the qualitative and quantitative characteristics of cuticular chemical components. This study hypothesizes that different ant species respond to temperature changes in different ways and that such differences may be associated with cuticle hydrocarbons (CHCs) and fatty acids. As model ant species, Atta sexdens, Odontomachus bauri and Ectatomma brunneum were used for experimental analyses. Ants were submitted to a water bath for 5 h at different temperatures, and their CHCs and fatty acids were identified and quantified, followed by correlating these chemical compounds with temperature variations and the survival. Temperatures below 30 °C did not affect the survival of the three species. E. brunneum had a higher percentage of survival at temperatures above 30 °C. O. bauri was the most sensitive species with 100% mortality at 40 °C. Survival was found to be unrelated to any of the identified fatty acids. However, CHCs underwent significant quantitative and qualitative variation, as shown by an increased percentage of CHCs with longer chain length of linear alkanes at temperatures above 30 °C. These increase enables these ants to maintain the integrity of their cuticle and survive at temperatures above 30 °C. It can be concluded that the forager ants studied respond differently to temperature variation and that changes in the conformation of CHCs are in line with the ecological characteristics of the different studied species because, they vary in terms of diurnal/nocturnal foraging and types of environments foraged. Among the three species, E. brunneum foragers were found to be more active under adverse conditions and more tolerant to temperature variation with the correspondingly appropriate changes in CHCs composition.

Indirect effects of mutualism: ant–treehopper associations deter pollinators and reduce reproduction in a tropical shrub

Animal-pollinated plants can be susceptible to changes in pollinator availability. Honeydew-producing treehoppers frequently occur on inflorescences, potentially enhancing ant-mediated negative effects on pollination services. However, the effect of ant-attended, honeydew-producing insects on plant reproduction remains uncertain. We recorded the abundance of treehoppers and ants on Byrsonima intermedia (Malpighiaceae), and monitored floral visitors in a Brazilian cerrado savanna. We manipulated the presence of ants and ant-treehopper associations on inflorescences to assess their effect on pollination and fruit formation. We used dried ants pinned to inflorescences to evaluate the effect of ant presence and ant identity on potential pollinators. Results show that the presence of treehoppers increases ant abundance on flowers and disrupts pollination by oil-collecting bees, decreasing the frequency and duration of floral visits and reducing fruit and seed set. Treehopper herbivory has no direct effect on fruit or seed production, which are independent of treehopper density. Pinned ants promote avoidance by floral visitors, reducing the number of visits. Ant identity mediates visitation decisions, with Ectatomma brunneum causing greater avoidance by floral visitors than Camponotus rufipes. Field videos show that pollinating beesare harassed by ants near flowers, prompting avoidancebehavior by the bees. This is the first demonstration of indirect effects by honeydew-gathering ants, via disrupted pollination, on plant reproduction in tropical cerrado savanna. Our results highlight the importance of studying other interactions near flowers, in addition to just observing pollinators, for a proper understanding of plant reproduction.

Intraspecific variation and influence of diet on the venom chemical profile of the Ectatomma brunneum Smith (Formicidae) ant evaluated by photoacoustic spectroscopy

Studies of venomous animals have shown that environmental and genetic factors contribute to determining the chemical composition of venom. It is well known that external effects cause differences in the toxicity, concentration, and prey specificity of venom. However, the influence of different factors on the chemical profile of Hymenoptera venom remains little explored. In view of this, the aim of this study was to evaluate intraspecific differences and the influence of diet on the chemical profile of Ectatomma brunneum venom using Fourier transform infrared photoacoustic spectroscopy. For the study of intraspecific variation of the venom, foragers were collected at locations with different environmental conditions, such as urban, intermediate, woodland and monoculture sites. To investigate the influence of diet on the venom, two colonies were sampled in the same area and were maintained in the laboratory under controlled diet conditions and at room temperature. The mid-infrared absorption spectra obtained were interpreted using discriminant function analysis. The results showed significant differences among the chemical profiles of the venoms of individuals from different environments and individuals exposed to a controlled diet in the laboratory, suggesting that venom composition was determined not only by genetic traits inherent to the species, but also by exogenous factors.

Comparisons of Protein and Peptide Complexity in Poneroid and Formicoid Ant Venoms

Animal venom peptides are currently being developed as novel drugs and bioinsecticides. Because ants use venoms for defense and predation, venomous ants represent an untapped source of potential bioactive toxins. This study compared the protein and peptide components of the poneroid ants Neoponera commutata, Neoponera apicalis, and Odontomachus hastatus and the formicoid ants Ectatomma tuberculatum, Ectatomma brunneum, and Myrmecia gulosa. 1D and 2D PAGE revealed venom proteins in the mass range <10 to >250 kDa. NanoLC-ESI-QTOF MS/MS analysis of tryptic peptides revealed the presence of common venom proteins and also many undescribed proteins. RP-HPLC separation followed by MALDI-TOF MS of the venom peptides also revealed considerable heterogeneity. It was found that the venoms contained between 144 and 1032 peptides with 5-95% of peptides in the ranges 1-4 and 1-8 kDa for poneroid and formicoid ants, respectively. By employing the reducing MALDI matrix 1,5-diaminonapthalene, up to 28 disulfide-bonded peptides were also identified in each of the venoms. In particular, the mass range of peptides from poneroid ants is lower than peptides from other venoms, indicating possible novel structures and pharmacologies. These results indicate that ant venoms represent an enormous, untapped source of novel therapeutic and bioinsecticide leads.

Fourier transform infrared photoacoustic spectroscopy as a potential tool in assessing the role of diet in cuticular chemical composition of Ectatomma brunneum.

The cuticular chemical composition plays a significant role in the recognition of nest mates in social insects, thus functioning as a chemical signature of the colony. The structure of cuticular chemicals is subject to interference from genetic and exogenous factors, including diet. In this study, various colonies of the Ectatomma brunneum ant were removed from their natural environment and housed in a laboratory to monitor the response of the cuticular chemical composition to dietary changes. Analyses were performed using gas chromatography and Fourier transform infrared photoacoustic spectroscopy, which has not been previously used for this type of analysis. The results indicate that this method is useful for analyzing biological and natural systems. We observed changes in the chemical signature with food traces in the first 30 days under feed control. Therefore, genetic information may not be the only criterion that can be used to describe the chemical signature of a species; environmental variations also influence recognition signals. Furthermore, these results reinforce the reliability of the Fourier transform infrared photoacoustic spectroscopy method.

Chemical Composition of Metapleural Gland Secretions of Fungus-Growing and Non-fungus-growing Ants

The metapleural gland is exclusive to ants, and unusual among exocrine glands in having no mechanism for closure and retention of secretion. As yet, no clear conclusion has been reached as to the function of metapleural gland secretion. Metapleural gland secretions were investigated for fungus-growing ants representing the derived attines Trachymyrmex fuscus, Atta laevigata, and Acromyrmex coronatus, the basal attines Apterostigma pilosum and Mycetarotes parallelus, and non-fungus-growing ants of the tribes Ectatommini (Ectatomma brunneum) and Myrmicini (Pogonomyrmex naegeli). Our results showed that the secretions of leaf-cutting ants (A. laevigata and A. coronatus) and the derived attine, T. fuscus, contain a greater variety and larger quantities of volatile compounds than those of myrmicine and ectatommine ants. The most abundant compounds found in the metapleural glands of A. laevigata and A. coronatus were hydroxyacids, and phenylacetic acid (only in A. laevigata). Indole was present in all groups examined, while skatole was found in large quantities only in attines. Ketones and aldehydes are present in the secretion of some attines. Esters are present in the metapleural gland secretion of all species examined, although mainly in A. laevigata, A. coronatus, and T. fuscus. Compared with basal attines and non-fungus-growing ants, the metapleural glands of leaf-cutting ants produce more acidic compounds that may have an antibiotic or antifungal function.

Description of the species of Dicoelothorax Ashmead (Chalcidoidea, Eucharitidae) and biology of D. platycerus Ashmead

Descriptions of the adults of the two species of Dicoelothorax Ashmead, Dicoelothorax parviceps and Dicoelothorax platycerus, and the eggs, planidia and pupae of Dicoelothorax platycerus Ashmead are provided. Females of Dicoelothorax platycerus deposit their eggs on the underside of leaves of Pseudabutilon virgatum (Cav.) Fryxell (Malvaceae). The host of Dicoelothorax platycerus is Ectatomma brunneum Smith (Formicidae: Ectatomminae).

Ant nest architecture and seed burial depth: Implications for seed fate and germination success in a myrmecochorous savanna shrub

Placement of seeds in favourable microsites by inhumation in ant nests is considered a principal advantage of myrmecochory. However, nest chambers may be too deep to allow seedling emergence. In this case, successful germination requires secondary transport of seeds to shallower sites. Little is known about the architecture of nests of seed-dispersing ants and the locations within nests to which seeds are initially transported. These data are essential to assess the importance of secondary transport for germination success of seeds. We studied dispersal of Manihot esculenta subsp. flabellifolia seeds by Ectatomma brunneum ants in French Guianan savannas. We followed movements of seeds within nests by offering marked diaspores to foraging workers, observing transport into the nest, then excavating to determine locations of marked seeds. In 4 nests, chambers ranged from 2 to 40 cm deep. Because elaiosomes are fed to brood, Manihot diaspores were initially transported to deep chambers, where brood was concentrated. Recovered diaspores had been carried to chambers 14–40 cm deep, all deeper than the maximum burial depth for emergence (= 13.8 cm) predicted from the mass (= 0.13 g) of Manihot seeds. Nest architecture thus makes secondary vertical transport of seeds crucial for dispersal success of this species. Failure of secondary transport may be an underestimated mortality factor in myrmecochorous plants.

Efeito do turno de coleta sobre comunidades de formigas epigéicas (Hymenoptera: Formicidae) em áreas de Eucalyptus cloeziana e de cerrado

This study aimed at evaluating the effect of collect time (day and night) on ant fauna attracted to baits in areas of Eucalyptus cloeziana (Myrtaceae) and cerrado. The ants were collected in Fazenda Boa Vista, Mannesmann Fi - El Florestal Ltda, Paineiras, Minas Gerais State. Eigthteen sample units were collected: 12 in E. cloezina and six in cerrado. Each sample unit consisted of three plots (25 x 35 m each). The plot consisted of 34 baits distributed in a grid pattern at 5 m intervals. The sampling was carried out in the diurnal and nocturnal period. The results obtained revealed that both type of vegetation (cerrado x Eucalyptus) and the collect time (day x night) had a significative influence on the epigaeic ant fauna. The ordination (DCA) indicated that collect time effect was more important to fauna structuration than the vegetation effect. Brachymyrmex sp.1, Brachymyrmex sp.2, Camponotus crassus Mayr, Camponotus rufipes (Fabricius), Cephalotes pusillus (Klug) and Ectatomma brunneum Smith were indicator species of nocturnal period, and Camponotus renggeri-Emery, Camponotus atriceps (Smith), Camponotus melanoticus Emery and Paratrechina sp.1 were indicators of nocturnal period.

Non-target impact of chlorpyrifos on soil arthropods associated with no-tillage cornfields in Brazil

The present study was undertaken to assess the side-effects of chlorpyrifos on springtails, ants and oribatid mites associated with the soil surface of no-tillage cornfields in Brazil. Three 0.3 ha cornfields were divided into plots and, during tasseling, the plants in areas to be treated were sprayed twice with insecticide, with a 3 day interval. Pitfall traps were used to sample soil arthropods 1 week before and 1, 2, 3, 4, 5 and 8 weeks after spraying. Principal components analysis detected no negative effect of insecticide chlorpyrifos on the assemblage of soil arthropods. Nonetheless, the activity of the ant Solenopsis saevissima (Fr. Smith) was lower 2 weeks after spraying but recovered afterwards, while the frequency of Ectatomma brunneum Fr. Smith, was significantly reduced only at the third week after spraying, and did not show any recovery until the end of the study. Chlorpyrifos did not decrease the overall abundance of Collembola. However, it had a significant impact on the members of the order Symphypleona, there being significantly lower captures of Sminthurides spp. soon after chlorpyrifos spraying without any sign of increase afterwards. There was no effect on oribatid mites. Our results, overall, suggest that the impact of chlorpyrifos on soil arthropods from tropical crop fields can be less severe than expected.

Ecological interactions among ants in the genus Linepithema, their phorid parasitoids, and ant competitors

Abstract. 1. Many ant species abandon foraging and retreat underground when parasitoids in the dipteran family Phoridae are present. Although the influence of phorids on ant foraging is well documented, their influence on interspecific competition is less studied. This study examined whether phorids influenced the competitive ability of host ants in the genus Linepithema at two sites in Brazil.2. The phorid Pseudacteon lontrae attacked Linepithema piliferum at one site, while the phorid Pseudacteon pusillus attacked an unknown Linepithema (Linepithema sp.) at the other site. Phorid parasitoids of Linepithema were far more common than phorids of other ant species.3. Despite a high abundance of phorids, it was difficult to conclude that they influenced competition. Captures in pitfall traps indicated that host Linepithema were most active during times of day when phorids were inactive.4. Camponotus rufipes and Brachymyrmex sp., the most common competitors of Linepithema sp. (60% of all interactions), dominated Linepithema sp. during the day regardless of phorids. Remaining ant species could not be evaluated individually because they interacted with Linepithema sp. infrequently.5. Ectatomma brunneum was the most common competitor of L. piliferum (58% of all interactions). The high abundance of phorids at this site made it impossible to evaluate interactions between E. brunneum and L. piliferum in the absence of phorids.6. Phorids seldom influenced exploitative competition by causing host Linepithema to abandon the bait when no ant competitors were present.