Alterations following a fire in a forest community of Alto Rio Xingu

This study records the consequences of fire upon the soil and structure of the Amazonian Forest of Gaucha do Norte, Mato Grosso state, Brazil (13degrees12'S and 53degrees20'W). For this, the number of individuals sampled in 1 ha of the forest, during a phytosociological survey completed 2 days before the accidental fire, was compared with the survivors recorded afterwards in the reinventory of the area taken 2 days and 10 months after the fire. For the surveys, the area of 1 ha was subdivided into 50 plots of 10 m x 20 m, and all the individuals with circumference at breast height (CBH) greater than or equal to 15 cm were sampled. Chemical analysis of the 30 soil samples collected 2 days before the fire were compared with those obtained 15 days and 1 year after the fire. It was seen that, soon after the fire, there was a significant increase in the nutrient levels in the soil, an increase in the pH and a decrease in the aluminum toxicity. However, after 1 year, losses by lixiviation resulted in a nutrient reserve in the soil of less than that before the fire. The tree mortality was extremely high (23.98%), particularly amongst the younger individuals of the population (93.68% of the total of deaths in the period). There was no significant reduction in the forest richness analyzed: 60% of the species had reduced populations after the fire, but just four species were locally extinct. Results, however, demonstrated a role for fire in the selection of resistant species or those adapted to fires, since some species demonstrated a greater tolerance to the fire than others. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Seed removal by ants from faeces produced by different vertebrate species

Ants frequently harvest seeds from faeces of frugivorous vertebrates. By transporting these seeds to nests, ants may influence seed dispersal success of plants. Seed removal by ants from vertebrate faeces is influenced by the seed species involved. Faeces from different vertebrates differ in chemical composition and physical characteristics. It remains unclear, however, whether the faeces itself affects the ant-seed interaction. In this study experimental seed-containing faecal portions were prepared using defecations of birds, marsupials, and monkeys and seeds of two aroids (Philodendron corcovadense and P. ppendiculatum, Araceae) and one liana species (Schlegelia parviflora, Bignoniaceae). Faecal portions were arranged along a transect established in the understory of a lowland rainforest in southeast Brazil. For P. appendiculatum the probability of detection and the proportion of seeds removed were identical between marsupial and monkey faeces. For P. corcovadense and S. parviflora, the probability of detection was affected by seed species and, apparently, also by the interaction between seed species and type of faeces (P = 0.097), but not by the type of faeces itself (bird or monkey). Both factors (i.e., seed species and type of faeces) affected the proportion of seeds removed (faeces type was marginally significant; P = 0.08), whereas the interaction between them was not significant. The results indicate that seed species affects seed removal by ants, while the type of faeces probably interacts with seed traits to influence faeces detection.

Short-term changes caused by fire and mowing in Brazilian Campos grasslands with different long-term fire histories

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Spatial-temporal distribution of fire-protected savanna physiognomies in Southeastern Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Contrasting responses to induction cues by ants inhabiting Maieta guianensis (Melastomataceae)

As duas formigas que mais comumente se associam com a mirmecofita de sub-bosque Maieta guianensis (Melastomataceac) respondem de maneiras diferentes a simulac (o) over tilde es experimentais de herbivoria. Enquanto Pheidole minutula & induzida tanto por danos fisicos e extratos de tecido foliar, Crematogaster laevis 6 induzida apenas pelos danos fisicos. Sugerimos que tal variac (a) over tildeo interespecifica em respostas induzidas e comum e pode influenciar a qualidade das defesas contra herbivoros que as formigas oferecem as plantas que elas ocupam.

Interspecific variation in the defensive responses of obligate plant-ants: experimental tests and consequences for herbivory

The aggressive behavior of ants that protect plants from herbivores in exchange for rewards such as shelter or food is thought to be an important form of biotic defense against herbivory, particularly in tropical systems. To date, however, no one has compared the defensive responses of different ant taxa associated with the same plant species, and attempted to relate these differences to longer-term efficacy of ant defense. We used experimental cues associated with herbivory-physical damage and extracts of chemical volatiles from leaf tissue-to compare the aggressive responses of two ant species obligately associated with the Amazonian myrmecophyte Tococa bullifera (Melastomataceae). We also conducted a colony removal experiment to quantify the level of resistance from herbivores provided to plants by each ant species. Our experiments demonstrate that some cues eliciting a strong response from one ant species elicited no response by the other. For cues that do elicit responses, the magnitude of these responses can vary interspecifically. These patterns were consistent with the level of resistance provided from herbivores to plants. The colony removal experiment showed that both ant species defend plants from herbivores: however, herbivory was higher on plants colonized by the less aggressive ant species. Our results add to the growing body of literature indicating defensive ant responses are stimulated by cues associated with herbivory. However, they also suggest the local and regional variation in the composition of potential partner taxa could influence the ecology and evolution of defensive mutualisms in ways that have previously remained unexplored.

Proventriculus of Cephalotes ants: A structural and comparative analysis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analysis of Ant Communities Comparing Two Methods for Sampling Ants in an Urban Park in the City of São Paulo, Brazil

This study aimed to analyze the species composition and functional groups of the ant community and to assess the efficiency of two sampling methods, pitfall and leaf litter sampling, in an urban park. A total of 1,401 ants were collected, which belonged to six subfamilies and 36 species. The predominant species was Wasmannia auropunctata (present in 45.36% of the samples), while the functional group of opportunistic ants were the most frequent (present in 83.75% of the samples) and abundant (95.29% of the total collected specimens) functional group. The Jaccard Similarity Index showed a low similarity between the two sampling methods, as the difference of the number of individuals for each species between these two methods was not significant in only one case (Linepithema sp. 1, p = 0.4561). The fungus-growing and cryptic ants were more collected in leaflitter samples (p<0.0001; p = 0.0348 respectively). Although there was no significant difference (p = 0.6397) between the two sampling methods for the total individuals of opportunistic ants, more species of this group were collected in pitfall traps. This difference was not significant because of the high presence of W. auropunctata, an opportunistic ant, in samples of leaf litter. Due to the predominance of tramp ants in the studied area, this article illustrates the importance of green urban areas in ant control strategies, since these sites could be used as a source of new colonization for these ants. Furthermore, the combination of the two sampling methods seems to be complementary for obtaining a more complete picture of the ant community.

A simple graphical model of small mammal succession after fire in the Brazilian cerrado

We studied the succession of small mammal species after fire in the cerrado (Neotropical savanna) of Central Brazil. Populations of small mammals were sampled with live-trapping techniques in a series of nine sites of different successional age, ranging from 1 to 26 years after fire. Ten species of small mammals were captured through all the seral stages of succession. Species richness ranged from two to seven species by seral stage. The species were arranged in different groups with respect to abundance along the succession: the first was composed of early successional species that peaked <2 years after fire (Calomys callosus, C. tener, Thalpomys cerradensis, Mus musculus, Thylamys velutinus); the second occurred or peaked 2-3 years after fire (Necromys lasiurus, Gracilinanus sp., Oryzomys scoth). Gracilinanus agilis peaked in the last seral stage. Species richness of small mammals showed an abrupt decrease from an average of four species immediately after fire to two species 5-26 years after the last fire. We propose a simple graphical model to explain the pattern of species richness of small mammals after fire in the cerrado. This model assumes that the occurrence of species of small mammals is determined by habitat selection behavior by each species along a habitat gradient. The habitat gradient is defined as the ratio of cover of herbaceous to woody vegetation. The replacement of species results from a trade-off in habitat requirements for the two habitat variables.

Questioning the implementation of habitat corridors: a case study in interior São Paulo using ants as bioindicators

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Attractiveness of copperleaf-based bait to leaf-cutting ants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Field methods for the study of ants in sugarcane plantations in Southeastern Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Description of an injury in a human caused by a false tocandira (Dinoponera gigantea, Perty, 1833) with a revision on folkloric, pharmacological and clinical aspects of the giant ants of the genera Paraponera and Dinoponera (sub-family Ponerinae)

A partir de um acidente causado pela picada de uma formiga falsa tocandira na mão de um pescador amador, os autores descrevem os achados clínicos locais observados, tais como edema, eritema e dor excruciante e a evolução do envenenamento, que cursou com fenômenos sistêmicos imediatos, como sudorese fria, náuseas, vômitos, mal estar, taquicardia e linfadenopatia axilar à esquerda. Após três horas, a dor intensa persistia e o paciente apresentou um episódio de hematoquesia, sem história anterior de enfermidades do trato digestivo, hematológicas ou vasculares. O uso de analgésicos (Tramal® 300 mg/dia), água quente e gelo não melhorou a dor, que arrefeceu em oito horas, tendo permanecido por cerca de 24 horas. São apresentados ainda os aspectos folclóricos, farmacológicos e clínicos relacionados às picadas de tocandiras.

Functional ultrastructure of the midgut of the fire ant Solenopsis saevissima Forel 1904 (Formicidae : Myrmicinae)

Solenopsis saevissima has a midgut composed of columnar, regenerative, and goblet cells. The midgut epithelium was covered by a basal lamina. Outside the basal lamina, layers of inner oblique, circular, and outer longitudinal muscles were present. Columnar cells showed a basal plasma membrane containing numerous folds, mitochondria, and the nucleus. Rough endoplasmic reticulum, Golgi bodies, membrane bounded vacuoles, and spherocrystals were found in this region. The apical plasma membrane was constituted by microvilli, which were above a region rich in mitochondria. Regenerative cells were found in groups lying by the basal lamina. Goblet cells were associated with an ion-transporting mechanism between the haemolymph and the midgut epithelium. These cells were lying by the midgut lumen and large microvilli were evident, but the cytoplasmic features were similar to the columnar cells.

THAUMATOMYRMEX STRIPS MILLIPEDES FOR PREY - A NOVEL PREDATORY BEHAVIOR IN ANTS, AND THE 1ST CASE OF SYMPATRY IN THE GENUS (HYMENOPTERA, FORMICIDAE)

We describe, for the first time, the predatory behaviour of Thaumatomyrmex ants on millipedes of the family Polyxenidae, based on field observations of T. atrox and a field and laboratory study of T. contumax. The capture of the prey and the removal process of its body-covering setae by the ants before they eat the millipede are described. This specialized behaviour in at least two species of the genus, belonging to two distinct groups of species, indicates a general trend in Thaumatomyrmex. We coupled this study with a comparative morphological analysis of the mouthparts and digestive tube of these and other Thaumatomyrmex species. Also, we report the first case of sympatry in the genus, which suggests that Thaumatomyrmex includes several species. and not only one highly variable taxon, as hypothesized earlier.