Flight and Digging Effort in Leaf-cutting Ant Males and Gynes

et al. 2022

Sci Rep

Queens of Atta sexdens Forel (Hymenoptera: Formicidae) face biotic and abiotic environmental factors in the environment while establishing their nests. Biotic factors such as predation, microbial pathogens, successful symbiotic fungus regurgitation, excavation effort and abiotic factors such as radiant sunlight, temperature, density, and soil moisture exert selection pressures on ant queens. Biotic factors such as temperature and solar irradiation affect the survival of the initial colony differently, in different environments in the field. Queens of the leaf-cutting ant A. sexdens, were installed in sunny and shaded conditions to test this hypothesis. Two hundred A. sexdens queens were collected and individualized in two experimental areas (sunny and shaded), each in an experimental area (25 m2) in the center of a square (50 × 50 cm). Temperature, irradiance, nest depth, rainfall and queen mortality were evaluated. Atta sexdens colony development was better in the shaded environment, and the depth and volume of the initial chamber, fungus garden biomass and number of eggs, larvae, pupae and workers were greater. The queen masses were similar in both environments but mortality was higher in the sunny environment. The worse parameter values for A. sexdens nests in the sunny environment are due to the greater solar irradiance, increasing the variation range of the internal temperature of the initial chamber of the nest. On the other hand, the more stable internal temperature of this chamber in the shaded environment, is due to the lower incidence of solar irradiance, which is also more advantageous for queen survival and the formation and development of A. sexdens colonies. Shaded environments are a better micro habitat for nesting A. sexdens than sunny ones.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The ideal habitat for leaf-cutting ant queens to build their nests

et al. 2022

Sci Rep

“…Queens excavated a greater amount of soil in the artificially shaded (less dense and more humid) than in the forest habitat (denser and drier), which could also be explained by excavation effort. They remove small soil particles with their jaws in repeated bites to form the first chamber (Römer & Roces, 2015), and transport them outside their nest (Ribeiro, 1995; Camargo et al, 2011; Fröhle & Roces, 2012; Silva et al, 2015). Therefore, the harder and drier the soil, the greater the excavation effort and, consequently, the longer the period required to dig the soil.…”

Section: Discussionmentioning

confidence: 99%

“…The greater initial depth of A. sexdens nests in the artificially shaded soil (less dense and more humid) than in the forest and pasture environments (denser and drier) confirms the relationship between microclimate (i.e., temperature, soil density, and soil humidity) and nest foundation efficacy. Also, this indicates an evolutionary trade‐off between minimizing energy expenditure during excavation, which could significantly affect queen survival (Camargo et al, 2011), and maximizing the depth of the nest, increasing protection against inadequate environmental conditions (Camargo et al, 2011; Silva et al, 2015). Indeed, the excavation of a shallow chamber requires less energy, but the queens are potentially exposed to environmental stress, such as temperature changes and desiccation (Camargo et al, 2011, 2013).…”

Section: Discussionmentioning

confidence: 99%

Do soil density and humidity affect nest‐founding in leaf‐cutting ant queens?

Entomologia Exp Applicata

et al. 2022

The habitat choice of nest sites by founding queens of leaf‐cutting ants varies with abiotic factors such as temperature, soil density, and soil humidity. In this study, we tested the hypothesis that soil density and moisture affect excavation effort (i.e., excavation period, excavated soil amount, initial nest depth, initial chamber volume, and mortality) in queens of the leaf‐cutting ant Atta sexdens (L.) (Hymenoptera: Formicidae). Queens were placed in experimental areas in three natural soils in Brazil with varying density and moisture content. The excavated soil was collected, dried, and weighed, and digging period, nest depth, chamber volume, and queen mortality were evaluated after nest establishment. In artificially shaded habitats (less dense and more humid soil), the establishment of queens was greater, the period of nest foundation was shorter, and excavated soil amount, nest depth, and volume of the initial chamber were greater than in forest and pasture habitats (denser and drier soils). Also, queen mortality was lower in less dense, more humid soil. This indicates a trade‐off between maximizing the depth of the nest, to increase protection against inadequate environmental conditions, and minimizing energy expenditure during excavation, affecting their survival.

“…The factors such as temperature, humidity and plants could affect the development of fields colonies 32 . In the field is dement the higher energy used to excavate them and form the first chamber 25 – 28 .…”

Section: Discussionmentioning

confidence: 99%

Carbon dioxide levels in initial nests of the leaf-cutting ant Atta sexdens (Hymenoptera: Formicidae)

et al. 2021

Sci Rep

Claustral foundation of nests by Atta sexdens Forel (Hymenoptera: Formicidae) involves great effort by its queens, solely responsible for the cultivation of the fungus and care for her offspring at this stage. The minimum workers, after 4 months, open access to the external environment to foraging plants to cultivate the symbiotic fungus, which decomposes the plant fragments and produces gongilidea nodules as food for the individuals in the colony. Colony gas exchange and decomposition of organic matter in underground ant nests generate carbon dioxide (CO2) emitted into the atmosphere. We described the carbon dioxide concentration in colonies in the field. The objective was to evaluate the carbon dioxide concentration in initial A. sexdens colonies, in the field, and their development. The CO2 level was also measured in 4-month-old colonies in the field, using an open respirometric system fitted with an atmospheric air inlet. The CO2 level of the respirometric container was read by introducing a tube into the nest inlet hole and the air sucked by a peristaltic pump into the CO2 meter box. The CO2 concentration in the initial colony was also measured after 4 months of age, when the offspring production (number of eggs, larvae, pupae and adult workers) stabilized. Ten perforations (15 cm deep) was carried out in the adjacent soil, without a nest of ants nearby, to determine the concentration of CO2. The composition of the nests in the field was evaluated after excavating them using a gardening shovel and they were stored in 250 ml pots with 1 cm of moistened plaster at the bottom. The CO2 concentration was higher in field nest than in adjacent soil. The concentration of carbon dioxide in A. sexdens nests in the field is higher than in those in the soil, due to the production of CO2 by the fungus garden and colony.