ABSTRACT. Richness of epigaeic ants (Hymenoptera, Formicidae) in Eucalyptus spp. plantations with different ages in Rio Grande do Sul, Brazil. The present study describes the epigaeic ant communities in eucalyptus plantations in sandbank in Rio Grande do Sul State. Ant collections were performed in six plantations of Eucalyptus grandis Hill ex Maiden and Eucalyptus saligna Smith with ages varying between five to 31 years old. A total of 24 areas (four/area) were randomly selected for ant collections. In each one, three transects of 100 m were designed at intervals of 12 m. Along each transect, ten pitfall traps with sardine baits were placed, at intervals of 10 m for a 24-hour-period. A total of 21,033 ants were collected, belonging to five subfamilies, 12 tribes, 19 genera and 49 species. According to the jackknife estimator of first order, there was no significant difference between the ant communities richness considering the eucalyptus species (U = 81.500; g.l. = 1; P = 0.582) and the ages of the plantations (U = 2.504; g.l. = 3; P = 0.547). Results indicate that richness of ant species are not related to the species of eucalyptus and/or to the age of the forests planted in sandbanks.

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Qual é o Efeito do Uso do Solo sobre as Comunidades de Formigas?RESUMO -Estudos sobre as comunidades de formigas em agroecossistemas têm contribuído para o conhecimento do efeito das práticas agrícolas sobre as comunidades biológicas. O objetivo deste trabalho foi avaliar o efeito do uso do solo nas comunidades de formigas. Foi testada a hipótese de que há um decréscimo na riqueza de espécies de formigas e uma mudança na composição de espécies em habitats com uso mais intenso do solo. As formigas foram amostradas com iscas de sardinhas, armadilhas subterrâneas e por coleta direta em quatro habitats com diferentes usos do solo (mata secundária, início de sucessão vegetal, refl orestamento com Acacia e cultivo misto). A riqueza não diminuiu com a intensidade de uso do solo. Na área em início de sucessão vegetal, o número de espécies coletadas por iscas de sardinha foi signifi cativamente diferente do obtido pelas armadilhas subterrâneas. A composição de espécies teve uma pronunciada variação, sendo que a fauna de formigas epigéica e hipogéica do habitat com maior intensidade de uso do solo (cultivo misto) mostrou baixa similaridade com as comunidades de formigas dos outros três habitats. As espécies predadoras restringiram-se aos habitats com baixa intensidade de uso do solo (mata secundária e sucessão vegetal). Assim, a composição de espécies refl etiu melhor as mudanças funcionais nas comunidades de formigas ao uso do solo do que a riqueza de espécies. Os resultados podem ajudar a escolher o componente das comunidades de formigas mais adequado e que melhor corresponde à resposta da biodiversidade aos impactos causados pelas atividades agrícolas. PALAVRAS-CHAVE: Agroecossistema, biodiversidade, bioindicador, monitoramento ambiental, Formicidae ABSTRACT -Studies on ant communities in agroecosystems have contributed to the knowledge of the effect of agricultural activities on biological communities. The aim of this study is to explain the effect of soil use on ant communities. We tested the hypothesis that there was a decrease in ant species richness and a change in the species composition at habitats with more intense soil use. We collected ants using sardine baits, subterranean traps and direct sampling at four habitats with different soil use (secundary forest, Acacia forestry, initial stage of succession and mixed crops). The ant species richness did not decrease with intensity of soil use. In successional habitat the species numbers collected using sardine baits and subterranean traps were signifi cantly different. Species composition of communities had a pronounced variation, with the epigaeic and hypogaeic ant faunas of the habitat with high intense soil use (mixed crops) had low similarity with ant communities of the three other habitats. The predator species were restricted to habitats with low intensity of soil use. Then, species composition could better refl ect the functional changes on ant communities than species richness. Our data can help to choose the component of ant community that better refl ect...

Previous studies on the effects of environmental factors, such as altitude, latitude, temperature, deforestation, forest fragmentation, fire, and flood on the community structure of termites and ants were conducted in various regions of Brazil; few of them were carried out in the southernmost Brazilian state of Rio Grande do Sul. Here we describe termites and ants diversity at different sites along the four geomorphologic units of this state. We recorded 16 taxa of termites, of which three are new state records, increasing to 19 the number of termite species known to occur in the state. Accordingly, we also found 73 species and 115 morphospecies of ants, of which only one was a new record, raising to 265 taxa the number of ant species known to occur in the state. As expected, we found a higher species richness of ants than termites. The low richness of both groups relative to other Brazilian regions could be a consequence of the subtropical to temperate climate in the state, since most portions of the state are below 30o latitude, the study areas be above 500 m altitude, and other environmental characteristics of each site. We suggest a positive relationship between species richness of termites and altitude, while ant richness indicated an inverse relationship. However, our data are not conclusive, due to the low number of replications in each altitude, particularly for termites. This study is unique in presenting an updated checklist of termites and ants in the state of Rio Grande do Sul.

SummaryLaboratory tests with mated females of the leaf-cutting ants Acromyrmex striatus (Myrmicinae, Attini) were conducted to determine if the colony foundation is a solitary or a mutualistic process. We have also tested the effect of foundresses density and number of available areas in this process. Three bioassays were performed: with single foundresses; with paired foundresses; and with groups of 8 to 18 foundresses. The results suggest that the foundation can be by haplometrosis or pleometrosis, possibly depending on physical distances between or densities of foundresses. Foraging activity was common in haplometrotic queens and in foundress pairs, but no foraging occurred in groups of foundresses.