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.
This paper reports on ant and termite species inhabiting the mounds (murundus) found in three wetland sites in Santo Antonio da Patrulha. Ants and termites were found in 100% of the mounds of two sites and in 20% of those in the third site. Colonies of Camponotus fastigatus were found inhabiting all the mounds, while colonies of Brachymyrmex sp., Linepithema sp., Pheidole sp., and/or Solenopsis sp. were collected in less than 30% of the mounds. In the mounds of the three sites, colonies of Anoplotermes sp. and/or Aparatermes sp. termites were found together with the ant colonies. Another cohabiting termite species, Cortaritermes sp., was found only in the mounds of one site. The results suggest that C. fastigatus is the species building the mounds, with the other species, whether ants or termites, being the inquilines.
Variações Sazonais da Secreção Metapleural da Formiga Cortadeira Atta sexdens piriventrisSantschi (Myrmicinae: Attini), e Ausência de Efeito Fungicida Sobre o Entomopatógeno Beauveria bassiana (Bals.) Vuillemin RESUMO -Os mecanismos envolvidos na manutenção das colônias de insetos sociais livres de patógenos são aspectos importantes relacionados à biologia evolutiva do grupo. No caso das formigas, tem sido sugerido que a secreção das glândulas metapleurais teria importante papel na assepsia da colônia. Neste trabalho, as diversas subcastas de operárias da formiga cortadeira Atta sexdens piriventris Santschi foram comparadas quanto à presença de secreção metapleural ao longo de um ano. Simultaneamente, a atividade tópica da secreção foi testada em operárias tratadas com o fungo entomopatogênico Beauveria bassiana (Bals.) Vuillemin. De acordo com a largura média da cápsula cefálica, foram definidas seis subcastas de operárias: jardineira, mínima, média, grande, máxima e soldado. Foi encontrada uma correlação positiva entre subcasta e comprimento do reservatório metapleural. As subcastas apresentaram diferenças significativas na presença de secreção metapleural ao longo do ano exceto nos meses de abril, maio, julho e novembro. Foi observada uma correlação positiva entre as temperaturas médias sazonais e presença de secreção metapleural. Foram registradas altas freqüências de operárias de todas subcastas infectadas por B. bassiana durante os bioensaios, indicando que a secreção metapleural não tem atividade fungicida contra esse patógeno. Os resultados sugerem que a secreção metapleural não está entre os principais mecanismos de assepsia das colônias de A. sexdens piriventris.PALAVRAS-CHAVE: Insecta, formigas cultivadoras de fungo, glândula metapleural, fungo entomopatogênico, controle biológico.ABSTRACT -Mechanisms involved in maintaining colonies of social insects free of pathogens are among the main aspects of interest in the evolutionary biology of this group. For ants, it has been suggested that secretion from the metapleural glands play an important role in colony asepsis. In this study, different worker subcastes of the fungus-growing ant Atta sexdens piriventris Santschi were compared in relation to presence of metapleural secretion during a year. At the same time, the topical activity of the secretion was tested on workers treated with the entomopathogenic fungus Beauveria bassiana (Bals.) Vuillemin. Based on the mean width of the cephalic capsule, six worker subcastes were defined: gardener, minor, media, large, major and soldier. A positive correlation between worker subcaste and metapleural reservoir length was observed. Significant differences for presence of metapleural secretion were found throughout the year among subcastes, except in April, May, July and November. A positive correlation between seasonal mean temperature and presence of the metapleural secretion was observed. High frequencies of infected workers of all subcastes were observed during bioassays with inoculation of B. bassiana, indicati...
In the temperate zones, termites play a minor ecological role, while, in the tropics, they dominate among the decomposing invertebrates, corresponding to about 10% of the total animal biomass and up to 95% of the soil insect biomass. At the same time, the tropical zones have more productive environments, lower climatic variation, greater ecological stability, and are richer in species. In this study, we evaluated termite species richness, composition, and trophic groups in 14 sites at different altitudes distributed in the State of Rio Grande do Sul, Southern Brazil from previous published surveys. We tested whether there would be a pattern linking those three variables to altitude and bioclimatic factors. We found no significant correlation between species richness and altitude. Bioclimatic variables did not explain the differences in species composition neither in functional group. However, species number, though not statistically different, and composition varied among sampling sites. We suggest that further surveys should be conducted along with greater collection effort and number of sampled sites as to provide a better understanding of the factors affecting the termite fauna of Southern Brazil.Ausência de Relação Entre Riqueza, Grupo Funcional e Variáveis Ambientais para Térmitas (Insecta: Isoptera) no Sul do BrasilResumo. Nas zonas temperadas, os térmitas têm um papel ecológico reduzido, enquanto que, nos trópicos, dominam entre os invertebrados decompositores e correspondem a cerca de 10% do total da biomassa animal e quase 95% da biomassa de insetos de solo. Ao mesmo tempo, as zonas tropicais possuem ambientes mais produtivos, menor variação climática, maior estabilidade ecológica e riqueza de espécies. No presente trabalho, avaliamos a riqueza, composição e os grupos funcionais dos térmitas de 14 localidades em diferentes altitudes no Rio Grande do Sul, sul do Brasil, a partir de dados já publicados. Testamos se existiria um padrão relacionando essas três variáveis à altitude e aos fatores bioclimáticos. Os resultados não mostraram correlação significativa entre riqueza de espécies e altitude, assim como os fatores bioclimáticos não explicaram a variação na composição de espécies e dos grupos funcionais. No entanto, o número, embora não significativo, e a composição de espécies foram diferentes entre os locais de coleta. Sugerimos a ampliação dos levantamentos, com maior esforço amostral e maior número de pontos amostrados, para identificar os fatores ambientais que influenciam a termitofauna do sul do Brasil.
-Maté crop, Ilex paraguariensis, is the economic base of several municipalities of Rio Grande do Sul. Despite the fact of presenting hundreds of associated insects, family Formicidae has not been registered yet. Therefore, aiming to identify ant species visiting I. paraguariensis, collections were made in two maté crop areas, one with healthy plants and the other with plants attacked by Hedypathes betulinus, and in a third small area. At the same time, tests with termites to simulate possible herbivores were conducted in order to evaluate predator activity of the ants which forage in I. paraguariensis. Considering the evaluated areas, sixteen ant species were found in maté. Significant interaction between ants and extrafloral nectaries in I. paraguariensis was not observed, and differential protection of leaves (with extrafloral nectaries) compared to stem (without extrafloral nectaries) did not occur. The greatest occurrence of ants in maté with Homoptera, as well as nesting in galleries left by H. betulinus (Cerambycidae) suggests that ants are only exploring resources provided by other insects.KEY WORDS: Insecta, Hedypathes betulinus, ant-plant interactions.RESUMO -A cultura de erva-mate, Ilex paraguariensis, base econômica de vários municípios do Rio Grande do Sul, possui mais de uma centena de insetos associados, no entanto, sem registros da família Formicidae. Assim, visando identificar as espécies de formicídeos que visitam I. paraguariensis, foram realizadas coletas em duas áreas de uma monocultura, uma com plantas sadias e outra com plantas atacadas por Hedypathes betulinus, e em um pequeno plantio dessa espécie. Paralelamente, foram conduzidos testes com térmitas, simulando possíveis herbívoros, para avaliar a atividade predatória das formigas que forrageiam em I. paraguariensis. Considerando as três áreas avaliadas, foram encontradas dezesseis espécies de formigas na erva-mate. Não foi observada interação significativa entre formigas e nectários extraflorais em I. paraguariensis, não tendo ocorrido uma proteção diferencial das folhas (com nectários extraflorais) em relação ao caule (sem nectários extraflorais). A maior ocorrência de formigas na erva-mate com homópteros, bem como nidificando nas galerias deixadas pelo cerambicídeo H. betulinus sugere que as formigas estão apenas explorando recursos proporcionados por outros insetos. PALAVRAS-CHAVE: Insecta, Hedypathes betulinus, interações formigas-plantas.A associação formigas/plantas tem sido documentada, principalmente, naquelas plantas com nectários extraflorais, cuja secreção fornece uma fonte rica em carboidratos, tornando-se interessante essa interação quando os formicídeos passam a fornecer proteção diferencial contra insetos herbívoros (Bentley 1977a, b;Oliveira & Oliveira-Filho 1991). Nas regiões com plantas nectaríferas a densidade de formigas é alta, sugerindo que parte utiliza o néctar extrafloral como item alimentar. Entretanto, várias espécies de formicídeos também podem utilizar o "ordenhamento" de coccídeos e membracídeos para...
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