Influence of Cave Size and Presence of Bat Guano on Ant Visitation

This is the first study which evaluated the influence of cave size and presence of bat guano in ant visitation in Brazilian caves. We provide a list of the ants associated with 27 caves in northeastern Brazil, an area situated in the transition between Cerrado (Brazilian savanna) and Amazon Domain. The study was conducted between January and August 2010. We recorded 24 ant species inserted into 12 genera, 10 tribes, and six subfamilies. The size of the cave and the presence of guano did not influence the richness of ants, and most of the caves had single species. Camponotus atriceps was the species with the larger distribution, being collected in five caves. In addition, we discuss geographic distribution of records and possible ecological roles of ants in cave environments

A New Protocol Using Artificial Seeds to Evaluate Dietary Preferences of Harvester Ants in Semi-arid Environments

The preferences of seed intake by harvester ants (Pogonomyrmex spp.) have been debated for a long time, mainly due the lack of repeatable methods to draw clear conclusions. However, several characteristics of the food resource are well recognized as the drivers of such selective predation. For instance, resource quality (i.e., availability of carbohydrates, lipids, and proteins) is one factor that could explain the observed foraging patterns of Pogonomyrmex species. In this sense, experimental approaches using artificial resources (e.g., synthetic seeds/diaspores) have provided an useful and alternative tool to study ant’s food foraging behavior. Therefore, it is expected that the use of artificial seeds also could offer a versatile way to assess the influence of resource quality exert on the resource selection by harvester ants. On the other hand, empirical experiments involving harvester ants and artificial seeds are still rare in the literature and it is not known if such methodology is efficient with different Pogonomyrmex species. In this study carried out in a Neotropical arid environment of central Mexico, we tested a simple but fundamental question: Do harvester ants (Pogonomyrmex barbatus) predate artificial seeds with manipulated nutrient content (lipids and proteins) in the field? We found that the proportion of native seeds removed was lower than the proportion of artificial seeds removed. However, we found no difference between the removal of artificial seeds containing only lipids and the seeds containing lipids + proteins. These findings indicate that the artificial seeds synthesized by us could be an effective method to test different ecological hypothesis involving harvester ants. Moreover, our empirical experiment offers a benchmark to study the influence of resource quality on the food foraging behavior of harvester ants in Neotropical arid environments

Temperature Influence on Species Co-Occurrence Patterns in Treefall Gap and Dense Forest Ant Communities in a Terra- Firme Forest of Central Amazon, Brazil

In this study we evaluated the influence of temperature and species co-occurrence on the structure of an ant community of treefall gaps and surrounding dense forests in a terra-firme forest of Central Amazon, Brazil. For this, we collected ants at different hours, and at the time of each collection we measured the temperature of the environment. Even with the difference in the temperature variation and variation throughout the day, there was no difference in the richness and abundance of ants among the environments. Also, the ant species are distributed randomly and independently of one another in both studied environments in accordance with a null model (C-score). However, although not influenced by temperature, the ant composition of treefall gaps was different from the ant community of the surrounding dense forest. Possibly the composition and ant foraging in environments of treefall gaps and surrounding dense forests are not only influenced by temperature, but also by the interaction of this factor with the structural complexity of vegetation in terms of sites available for nesting and feeding, and other microclimatic factors. This generates a difference in ant composition of both environments. In addition, the structuring of ant community in tropical rain forests may actually be stochastic or neutral within each environment

Detection and use of foraging trails of the leaf-cutting ant Atta laevigata (Hymenoptera: Formicidae) by Amphisbaena alba (Reptilia: Squamata)

Se provee información sobre un individuo de Amphisbaena alba (Reptilia: Squamata) que reconoce y usa un sendero de la hormiga cortadora de hojas Atta laevigata (Hymenoptera: Formicidae) en la sabana neotropical de Brasil. También registramos y describimos movimientos de desviación de obstáculos y el comportamiento de A. alba para reconocer el sendero de hormigas. Adicionalmente, discutimos cómo el mimetismo químico de A. alba pudiera estar involucrado en nuestra observación y sugerimos que esta relación va más allá de un simple inquilinismo, donde A. alba puede usar el nido como un sitio de reposo y alimentación para otros organismos asociados con nidos de hormigas cortadoras

Thermal Tolerance of Honeybees (Apis mellifera L.) Changes Across an Elevation Gradient in the Mexican Transition Zone

The objective of this study was to determine the critical thermal minimum [CTmin], critical thermal maximum [CTmax], and thermal tolerance range of A. mellifera at three different elevations located in the Mexican Transition Zone: 11; 1,324, and 3,304 m.a.s.l. In general, we found that the CTmin of A. mellifera was lower at the site with the highest elevation (i.e., they tolerate colder temperatures). At the same time, the CTmax remained constant across the three studied elevations, revealing higher plasticity for cold tolerance rather than heat. Moreover, we did not find evidence that the body mass of the individuals was associated with their thermal tolerance at any of the three sampled elevations. Our findings suggest processes of local adaptation of A. mellifera populations in environmentally contrasting sites, allowing them to expand their range of distribution, which could be useful in predicting responses to future environmental change

On the Effectiveness of Hand Collection to Complement Baits When Studying Ant Vertical Stratification in Tropical Rainforests

Choosing an appropriate sampling method to study ants is a key factor since distinct sampling methods can capture distinct ant fauna and, therefore, leading to bias in the interpretation and conclusion of the patterns observed. Despite it is well known that the ant fauna is vertically stratified, some of the sampling methods cannot be used throughout the whole vertical stratum (e.g., fogging and Winkler extractor). Here we compared the complementarity of hand collecting and baiting (with tuna or honey) in ant surveys focused on the stratification of the ant fauna in a tropical rainforest in Mexico. We found a total of 44 ant species, belonging to 17 genera and five subfamilies. The three sampling methods were clearly complementary at both the forest floor and canopy levels, even with as little as 10 minutes of search time for hand collecting. The ant species composition differed among sampling methods at both vertical strata. Hand collecting yielded higher ant species richness and more exclusive species than either bait at both vertical strata, but both tuna and honey baits also led to the detection of some (though fewer) exclusive ant species. The combination of hand collecting, tuna, and honey baits should thus be considered complementary tools for ant inventories, since using the two methods together yielded more complete inventories at both vertical strata. An additional advantage is that both methods can be used in both strata, ensuring that data in different vertical strata are comparable and allowing more reliable comparisons among these different habitats

Understanding the Complex Structure of a Plant-Floral Visitor Network from Different Perspectives in Coastal Veracruz, Mexico

Our premise was to understand the basic structure of the flower-flower visitor community at La Mancha in Veracruz, Mexico. We used network analyses to study the structure of this community. In particular, to analyze, (1) if flower color and shape (“as a limited portion of the traditional floral syndromes definition”) were linked to the arrival of certain floral visitors, (2) if visits to flowers were generalist, specific and/or modular; and (3) which plant species, if any, in the core of the network could affect the stability of floral visitors. In order to analyze the organization of the plant-floral visitor community, we prepared network graphics using Pajek, nestedness (as NODF) with Aninhado, and modularity with the SA algorithm. The network obtained was nested suggesting that generalist species (with the most associations) were interacting with specialists (with fewer associations). Furthermore, floral visitors (Hymenoptera, Diptera, Lepidoptera and Trochiilidae) did not exhibit a particular preference for a specific flower color or shape, each pollinator group visited most flowers/colors/shapes considered. The same was similar for all 14 resulting modules. As in other studies, we suggest that pollination leans to generalization rather than to specialization. We suggest that maybe seasonality/food resource could be the factors to analyze as the next step in floral visits which may be the answer to modularity in this seasonal ecosystem

Caracterización morfológica de los nectarios extraflorales en especies vegetales de la Amazonia brasileña

Background and Aims: Extrafloral nectaries (EFNs) are secretory glands of an aqueous solution composed mainly of sugars, amino acids and lipids, frequently used as food resource by ants, which tend to protect their host plants against herbivorous insects. Although the Amazon forest is recognized worldwide for its high plant diversity, few studies have been carried out in the region that characterize the different morphotypes of EFNs. In this context, our main aim was to perform a brief morphological description of EFNs in the Brazilian Amazonian rainforest. Methods: We established a plot of 6250 m2 in ten forest fragments situated in the state of Acre, Brazilian Amazon. In these plots, we performed intensive field surveys to locate EFN-bearing plant species. Subsequently, we used scanning electron microscopy images to morphologically characterize the EFNs. The morphological descriptions included information about the life form of EFN-bearing plant species, morphotypes of EFNs and their location in different plant structures. Key results: We morphologically characterized 67 EFN-bearing plant species, distributed in 28 genera and 19 families. The botanical families with the highest taxonomic representativeness were Fabaceae, Bignoniaceae and Malpighiaceae. Lianas were the life form with the largest number of EFN-bearing plant species, while elevated EFNs were the most frequent morphotype. Conclusions: The high frequency of elevated EFNs evidences the importance of the ant defense system against herbivory in these Brazilian Amazonian forests, since it has been documented in others works that this morphotype secretes a larger nectar volume, which is an advantage in relation to the attraction potential. Finally, our results indicate the existence of a high diversity of EFN-bearing plant species in this region of the Brazilian Amazon, and an important morphological diversity of associated extrafloral nectaries.Antecedentes y Objetivos: Los nectarios extraflorales (NEFs) son glándulas secretoras de una solución acuosa compuesta principalmente de azúcares, aminoácidos y lípidos, frecuentemente utilizada como recurso alimenticio por hormigas, que tienden a proteger sus plantas hospederas contra insectos herbívoros. Aunque la selva amazónica es reconocida mundialmente por su alta diversidad de plantas, pocos estudios se han realizado en la región que caracterizan las diferentes formas de NEFs. En este contexto, nuestro principal objetivo fue realizar una descripción morfológica de los NEFs en una selva amazónica brasileña. Métodos: Establecimos una parcela de 6250 m2 en diez fragmentos de bosque situados en el estado de Acre, Amazonía Brasileña. En estas parcelas, realizamos recorridos de campo intensivos para localizar especies de plantas portadoras de NEFs. Posteriormente, utilizamos imágenes de microscopía electrónica de barrido para caracterizar morfológicamente los NEFs. Las descripciones morfológicas incluyeron información sobre la forma de vida de las especies de plantas portadoras de NEFs, morfotipos de NEFs y su ubicación en las diferentes estructuras de la planta. Resultados clave: Caracterizamos morfológicamente 67 especies de plantas portadoras de NEFs, distribuidas en 28 géneros y 19 familias. Las familias botánicas con mayor representatividad taxonómica fueron Fabaceae, Bignoniaceae y Malpighiaceae. Las lianas fueron la forma de vida que presentó más especies de plantas portadoras de NEFs, mientras que los NEFs de tipo elevado fueron los más frecuentes. Conclusiones: La mayor frecuencia de NEFs de tipo elevado evidencia la importancia del sistema de defensa de hormigas contra la herbivoria en esta selva amazónica brasileña, ya que se ha documentado en otros trabajos que este morfotipo secreta un mayor volumen de néctar, lo que es una ventaja en relación con el potencial de atracción. Finalmente, nuestros hallazgos indican la existencia de una alta diversidad de especies de plantas portadoras de NEFs en esta región de Amazonía Brasileña, y una importante diversidad morfológica de nectarios extraflorales asociados

Postponing the production of ant domatia as a strategy promoting an escape from flooding in an Amazonian myrmecophyte

Background and Aims: Even when adapted to flooding environments, the spatial distribution, growing strategies and anti-herbivore defences of plants face stressful conditions. Here we describe the effects of flooding on carbon allocation on growth, domatia and leaf production, and the herbivory on the myrmecophyte domatia-bearing Tococa coronata Benth. (Melastomataceae) growing along river banks in the Amazon region. Methods: In an area of 80 000 m2 of riparian forest along the Juruena River we actively searched for individuals of T. coronata. In each plant we evaluated the size of the plant when producing the first domatium and determined its best predictor: (1) plant total height; (2) size of plants above flood level; or (3) length of time each plant spent underwater. We also compared the herbivory, internode elongation, foliar asymmetry and specific leaf weight between T. coronata individuals growing above and below the maximum flooding level. The distance to the river and the height of the first domatium produced were compared between T. coronata and its sympatric congener, T. bulifera. Key Results: We found that T. coronata invests in rapid growth in the early ontogenetic stages through an elongation of internodes rather than in constitutive anti-herbivore defences to leaves or domatia to exceed the maximum flooding level. Consequently, its leaf herbivory was higher when compared with those produced above the flooding level. Individuals with leaves above flood levels produce coriaceous leaves and ant-domatias. Thus, flooding seems to trigger changes in growth strategies of the species. Furthermore, T. coronata occurs within the flood level, whereas its congener T. bullifera invariably occurs at sites unreachable by floods. Conclusion: Even in conditions of high stress, T. coronata presents both physiological and adaptive strategies that allow for colonization and establishment within flooded regions. These mechanisms involve an extreme trade-off of postponing adult plant characteristics to rapid growth to escape flooding while minimizing carbon allocation to defence

Foraging ants on the extrafloral nectaries repel nectar thieves but not the effective pollinator of Vigna luteola (Fabaceae) in a Mexican coastal sand dune

While some studies have shown that ants that visit extrafloral nectaries may defend their host plants against potential herbivores, recent researches have shown that such ant-plant mutualism may be broken in some cases. For example, the presence of ants on plants could also drive away pollinators and seed dispersers. However, it is not yet known what mechanisms could favor that ant presence on plants does not affect other mutualistic interactions involving plants. In this work, we performed a series of field experiments to test the hypothesis that the presence of ants on EFNs located at the base of the inflorescences of Vigna luteola (Fabaceae) may have a negative effect on floral visitors but not on potential pollinators in a Mexican coastal sand dune. In general, we found that the presence of ants on the plants decreased the rate of flower visitation. However, we observed that the time of visitation of the effective pollinators the bee (Pseudocentron) sp. on the flowers was less compared to that of other floral visitors. This strategy may allow that ants cannot aggressively scare away the effective pollinators. In summary, we show that the effective pollinators of V. luteola present strategies that allow them to visit the flowers without being aggressively attacked by the ants that visit the extrafloral nectaries (EFNs). Therefore, the presence of ants on plants could have a dual function: protecting plants against potential herbivores as well as, filtering flowers against nectar thieves