Antônio José Mayhé-Nunes

The role of ants in the removal of non-myrmecochorous diaspores and seed germination in a neotropical savanna

Ants frequently interact with non-myrmecochorous diaspores on the ground in neotropical savannas. Our objective was to quantify the removal rate of these diaspores by ants and vertebrates in order to test the predator avoidance hypothesis, and to test how diaspore traits influence removal by ants and dispersal distance. We also investigated whether seed cleaning (removal of fruit matter simulating ant activity) can influence seed germination. We performed removal experiments with nine diaspore species in a reserve of cerrado savanna in south-east Brazil. Considerable differences in removal rates were found among the nine species. We found a positive linear relationship between lipid content and removal rates for five diaspore species. Vertebrate predation pressure was low for most species, limiting the benefits that ants can provide to plants to escape predators. Ants displace diaspores up to 25 m, which may increase the chance of a seed hitting a safe site. Smaller diaspores attain longer distances of dispersal than large ones. Seed cleaning increased the germination rate for five out of six species tested in greenhouse experiments. Ant activity can have relevant and possibly lasting effects on seed fate of plants adapted for vertebrate dispersal in the cerrado savanna.

Efeitos de fatores ambientais sobre a mirmecofauna em comunidade de restinga no Rio de Janeiro, RJ

The effects of environmental factors on the richness, diversity and abundance of ants were studied in the Restinga da Marambaia, south coast of Rio de Janeiro State, Brazil. The samples were taken using pitfall traps in August/2004 (winter) and March/2005 (summer) in three different vegetation types: (1) herbaceous ridge palmoid (homogeneous habitat); (2) shrub dune thicket and (3) ridge forest (heterogeneous habitats). At each habitat a range of environmental attributes was recorded: soil temperature and humidity, percentage of soil covering by litter and litter depth. Ninety-two ant species belonging to 36 genera and eight subfamilies were recorded. Density of ant species and abundance varied significantly between habitats and seasons; ant diversity varied only between habitats. Homogeneous habitat had lower ant species density, abundance and diversity than heterogeneous habitats. The two first variables were positively correlated with litter depth and both were higher in summer than in winter samples. There were more species of Ponerinae and Ectatomminae in heterogeneous than in the homogeneous habitat, whereas the Formicinae species were more abundant in the later.

Combate sistemático de formigas-cortadeiras com iscas granuladas, em eucaliptais com cultivo mínimo

The efficiency of a systematic application of baits against leaf-cutting ants was evaluated in a eucalypus plantation under a minimum cultivation system, in areas owned by Celulose Nipo-Brasileira S.A. (CENIBRA), in Belo Oriente, Minas Gerais, Brazil, from September to December 1996. Treatments consisted of applying a granulated bait with sulfluramide (0.3%) in a systematic manner in bulk and plastic bags at a dose of five grams every 6 m2 (T1) and 10 grams at each 12 m2 (T2). Mortality of colonies of leaf-cutting ants was evaluated 30 days after bait application. A. maximum of 396.3; 285.2; 59.3; 55.6; 29.6 and 14.8 colonies of Mycocepurus goeldii, Sericomyrmex sp., Acromyrmex subterraneus molestans, Atta spp., Acromyrmex balzani and Acromyrmex niger (Hymenoptera: Formicidae), respectively, was found per hectare. The efficiency of this granulated bait, applied in a systematic manner, varied with the method and species of leaf-cutting ants. Higher efficiency was obtained for A. subterraneus molestans, with 69.2% of dead colonies with the bait applied in bulk and 62.5% when it was applied in plastic bags. This shows that bait distribution in the eucalyptus plantation was performed at a larger spacing than the foraging area of leaf-cutting ants and/or that the dose was insufficient.

Fauna de formigas como ferramenta para monitoramento de área de mineração reabilitada na Ilha da Madeira, Itaguaí, RJ.

Ant species richness and diversity may be increased in more complex habitats because they provide more niches and diverse ways of exploiting the environmental resources. Because of the connection between the organisms and habitat characteristics, ants have been used as tools for environmental monitoring of disturbed areas. In this study the structure of the ant community was investigated in plots with different management strategies for the rehabilitation of a mined area at Ilha da Madeira, Itaguai, RJ, Brazil. A different and richer ant fauna was found in plots with more native tree species than in plots with a low number of tree species or without conservationist management.

Inventário estruturado de formigas (Hymenoptera, Formicidae) em floresta ombrófila de encosta na ilha da Marambaia, RJ

Ants are an important functional component in tropical forest due to their ecological roles, biomass and species diversity. Although the Atlantic Forest is one of the best studied ecosystems in Brazil, there is a lack of information about ant diversity in forest fragments of the state of Rio de Janeiro. The composition and richness of the ant fauna from atlantic slope rain-forest in Marambaia island-RJ were assessed by the structured inventory in an area of 0.6 ha. Pitfalls traps and hand collecting were used for sampling ants in the litter and on vegetation from January to July/2004. A total of 29 genera and 82 species were found in this survey. Ant abundance and richness were higher in March than in July samples. Eveness and diversity of ants in the samples were not affected by the time of the year. Collections of ants from dead twigs yielded an additional seven species and provided information about the ant biology. Sampling ants on plants resulted in 32 species but 12 species were not recorded in litter samples. Some species were recorded exclusively on vegetation, such as Pseudomyrmex, Crematogaster and Pachychondyla species. This study aims to contribute to the development of conservation priorities in one of the most threatened ecosystems in the world.

Geographic distribution of Atta robusta Borgmeier (Hymenoptera: Formicidae)

The available information regarding the geographic distribution of Atta robusta Borgmeier is confused and raised the necessity of revision of both its distribution and its endemic status. This paper ascertained the occurrence of A. robusta in restingas of Espirito Santo and Rio de Janeiro states, Brazil, through fieldwork, museum visits and bibliographical revision. No reference mentioned its occurrence out of restinga vegetation, as well as in states located south of Rio de Janeiro. We confirmed that A. robusta is endemic of restinga vegetation and it is restricted to the strip of the denominated Moist Oriental Tertiary Brazilian Coast. Such a distribution is possibly due to geographical and ecological barriers that obstruct its dispersion to other environments.

Influência da heterogeneidade da serapilheira sobre as formigas que nidificam em galhos mortos em floresta nativa e plantio de eucalipto

This study investigated the twig-nesting ants of native forest and eucalyptus plantations in southeast of Brazil. The diversity of twig-nesting ants was greater on native forest than on eucalyptus plantations. Native forest had a greater diversity of twig types, mainly of those used by ants. Overall ant richness was 12 species in native forest and 4 species in eucalyptus plantations. The characteristics of litter and microclimatic conditions may be responsible for the different ant fauna found on both vegetation types.

Teste da regra de equivalência energética para formigas de serapilheira: efeitos de diferentes métodos de estimativa de abundância em floresta ombrófila

The Energetic Equivalence Rule (EER) states that species tend to consume energy independent of their body size. Here, the EER was tested for litter ants using body size and abundance data. Rainforest ants were obtained using pitfall traps and Winkler extractor. The abundance data from the Winkler extractions confirmed the EER, while the pitfall traps rejected it. Combination of abundance from pitfall catches and Winkler extractions either confirmed or rejected the EER. Further studies should focus on the interaction between sampling techniques and habitat types in the test of EER for ant communities.

Revisionary notes on the fungus-growing ant genus Mycetarotes Emery (Hymenoptera, Formicidae)

Mycetarotes is a small genus of the exclusively Neotropical fungus-growing ants, that includes M. parallelus (Emery), M. senticosus Kempf, M. acutus Mayhe-Nunes and M. carinatus Mayhe-Nunes. We hereby revise historical and recent information regarding Mycetarotes species for the first time, providing an identification key to workers, diagnoses, synoptic illustrated redescriptions of the species, including those of sexuals when known, updates of distributional records, and nest pictures of M. carinatus and M. parallelus. We comment the taxonomy and phylogenetic relationships among Mycetarotes and related genera, and on their geographical distribution. The available biological information on the genus is summarized.

Caracterização de ninhos e atividade forrageadora de Trachymyrmex fuscus Emery (Hymenoptera, Formicidae) em plantio de eucalipto

Seven nests of T. fuscus Emery, 1834 have been studied for their structure. These nests, which opened at the soil surface, had two to four chambers located one above the other. Externally all of these nests presented a heap of brownish-yellow debris that was constituted basically by remains of vegetable material. The total nest population was, on average, 1,048 individuais. The diel pattern of foraging of this species was studied for four consecuti ve months on two nests. This activity occurred predominantly in the night period, and the workers transported, mainly, dry vegetation to the nest.