Epigaeic ants ina forest remnant in the state of Acre, Brazil and new records for the state.

Ants are considered an important group of invertebrates in terrestrial ecosystems, where they participate in important ecological processes between animals and plants, and they are considered good indicators of environmental impacts as well. Although the diversity of ants in the Amazon biome is already relatively well known, the ant fauna in the state of Acre, Brazil is still poorly known. The aim of this study was to carry out a survey of ants in a forest remnant located in the municipality of Plácido de Castro, Acre, using pitfall traps. Thirty-six species of ants were collected from six subfamilies and 18 genera. From the species confirmed, 11 (Cephalotes serraticeps, Gnamptogenys moelleri, Gnamptogenys triangularis, Neoponera apicalis, Neoponera commutata, Neoponera verenae, Mayaponera constricta, Megalomyrmex emeryi, Pachycondyla impressa, Pheidole araneoides and Odontomachus caelatus) are first records for Acre state, increasing our knowledge of the epigaeic ants that occur in this region of the Amazon. As formigas são consideradas um significante grupo de invertebrados nos ecossistemas terrestres, participando de importantes processos ecológicos entre animais e plantas, além de serem consideradas como bons indicadores de impactos ambientais. Apesar de a diversidade de formigas no bioma Amazônico já ser relativamente bem conhecida, a fauna de formigas do estado do Acre ainda é incipientemente estudada. O objetivo deste estudo foi realizar um levantamento de formigas em um remanescente florestal localizado no município de Plácido de Castro - Acre, utilizando armadilhas do tipo "pitfall trap". Foram coletadas 36 espécies de formigas, pertencentes a seis subfamílias e 18 gêneros. Das espécies confirmadas, 11 (Cephalotes serraticeps, Gnamptogenys moelleri, Gnamptogenys triangularis, Neoponera apicalis, Neoponera commutata, Neoponera verenae, Mayaponera constricta, Megalomyrmex emeryi, Pachycondyla impressa, Pheidole araneoides e Odontomachus caelatus) representam primeiros registros para o estado do Acre, aumentando o conhecimento acerca das formigas epigeias que ocorrem nesta região da Amazônia

Efeito do cultivo de milho Bt sobre a comunidade de formigas de solo.

Resumo

Rediscovery and reclassification of the dipteran taxon Nothomicrodon Wheeler, an exclusive endoparasitoid of gyne ant larvae

The myrmecophile larva of the dipteran taxon Nothomicrodon Wheeler is rediscovered, almost a century after its original description and unique report. The systematic position of this dipteran has remained enigmatic due to the absence of reared imagos to confirm indentity. We also failed to rear imagos, but we scrutinized entire nests of the Brazilian arboreal dolichoderine ant Azteca chartifex which, combined with morphological and molecular studies, enabled us to establish beyond doubt that Nothomicrodon belongs to the Phoridae (Insecta: Diptera), not the Syrphidae where it was first placed, and that the species we studied is an endoparasitoid of the larvae of A. chartifex, exclusively attacking sexual female (gyne) larvae. Northomicrodon parasitism can exert high fitness costs to a host colony. Our discovery adds one more case to the growing number of phorid taxa known to parasitize ant larvae and suggests that many others remain to be discovered. Our findings and literature review confirm that the Phoridae is the only taxon known that parasitizes both adults and the immature stages of different castes of ants, thus threatening ants on all fronts.Peer reviewe

Arboreal ant abundance tracks primary productivity in an Amazonian whitewater river system

Little is known about consumer productivity in the tropics despite the key feedbacks that animals impose on primary productivity. In the Amazon basin, seasonally flooded and unflooded forests exist side by side, and ants (Formicidae) dominate animal biomass. Although flooding has a direct negative effect on soil-dwelling ants, it is less clear whether flooding has indirect effects on arboreal ants via associated changes in tree communities. To test whether seasonal inundation by whitewater affects arboreal ants, we investigated ant communities in adjacent flooded and unflooded forests along a major whitewater river in central-western Amazonia. Whitewater-flooded forest exhibits higher primary productivity than unflooded forest. We thus hypothesized that forest type would affect the productivity and the foraging traits of arboreal ants and that these changes would be mediated by increases in plant-derived food for ants in flooded forest. We compared ant and plant communities between flooded- and unflooded-forest transects along the Juruá River in Amazonas, Brazil. We collected, identified, and counted terrestrial and arboreal ants, and we measured ant traits with putative relationships to foraging strategy. We also identified plant stems to characterize the abundance of ant food rewards. Flooding negatively affected the diversity and abundance of terrestrial ants but did not change the diversity of arboreal ants. Arboreal ants were more abundant and exhibited higher biomass in flooded forest than in unflooded forest. Arboreal ant traits also suggested that ants may rely more heavily on plant-derived food in flooded forest than in unflooded forest. These differences were associated with a higher abundance of plant stems predicted to contain ant food rewards in flooded forest than in unflooded forest. Our results indicate that the productivity of arboreal ants is affected by that of the underlying forest. Such effects may be mediated by the predominantly herbivorous foraging strategy of canopy ants, which would link ant populations closely to primary production and stoichiometry. Given ants’ important functional roles, these differences in ant productivity between forest types may have consequences for other arthropods and feedbacks to plants throughout the Amazon basin

Estudo preliminar sobre formigas num plantio de canola, Brassica napus L. (Brassicaceae), em Passo Fundo, Rio Grande do Sul, Brasil.

Resumo: No Brasil, a canola, Brassica napus, é associada a uma grande diversidade de artrópodes, destacando-se fitófagos, predadores e polinizadores que visitam o cultivo em busca de recursos alimentares. Apesar dos estudos já realizados na canola, ainda são escassas as informações acerca das formigas que ocorrem nessa cultura. Por isso, este estudo teve como objetivo realizar um levantamento preliminar desses insetos em uma área cultivada com canola no estado do Rio Grande do Sul. O estudo foi conduzido numa área experimental de 800 m2, da Embrapa Trigo, Passo Fundo, que foi plantada com o híbrido Hyola 433, durante dois anos, em maio de 2015 e em maio de 2016. As coletas de formigas foram realizadas com armadilhas-de-solo do tipo ?pitfall trap?, contendo solução conservante, e que ficavam no campo por sete dias. Após esse período, as formigas eram coletadas e a solução era reposta para a coleta da próxima semana. Em 2015, as coletas foram realizadas de junho a setembro (15 amostragens), e em 2016, de junho a outubro (20 amostragens). Foram coletados 414 indivíduos de formigas, distribuídos em quatro subfamílias (Dolichoderinae, Formicinae, Myrmicinae e Ponerinae), contemplando 31 espécies ou morfoespécies. A subfamília que predominou foi Myrmicinae (87,2%), que também apresentou o maior número de espécies identificadas (n=19). Exemplares de Pheidole foram os mais abundantes (76,8%) e também esse gênero foi o que apresentou a maior diversidade de espécies (10). As formigas Dorymyrmex jheringi, Pheidole cramptoni, Pheidole eidmanni e Pheidole industa estão sendo registradas pela primeira vez para o estado do Rio Grande do Sul, e, no caso da última citada, para o Brasil. O cultivo da canola apresentou uma grande diversidade de formigas, incluindo-se espécies fitófagas, predadoras e uma de parasita social de Acromyrmex: Pseudoatta argentina. Abstract: In Brazil, the oilseed rape, Brassica napus, is associated with a wide range of arthropods, especially phytophagous, predators and pollinators that visit the crop in search of food resources. Despite the studies already carried out on oilseed rape, information about the ants that occur in this crop is still scarce. Therefore, this study aimed to carry out a preliminary survey of these insects in an area cultivated with oilseed rape in the state of Rio Grande do Sul, Brasil. The study was conducted in an experimental area of 800 m2 of Embrapa Trigo, Passo Fundo, which was planted with the hybrid Hyola 433 for two years, in May 2015 and May 2016. Ant collections were carried out with pitfall traps containing a preservative solution, which stayed in the field for seven days. After this period, the ants were collected and the solution was replaced for the next week's collection. In 2015, collections were carried out from June to September (15 samples), and in 2016, from June to October (20 samples). A total of 414 ant individuals were collected, distributed in four subfamilies (Dolichoderinae, Formicinae, Myrmicinae and Ponerinae), comprising 31 species or morphospecies. The predominant subfamily was Myrmicinae (87.2%), which also had the highest number of identified species (n=19). Pheidole specimens were the most frequent (76.8%) and this genus was also the one with the highest species diversity (10). The ants Dorymyrmex jheringi, Pheidole cramptoni, Pheidole eidmanni and Pheidole industa are recorded for the first time for the state of Rio Grande do Sul and, in the case of the latter, for Brazil. Oilseed rape cultivation showed a great diversity of ants, including phytophagous, predatory species as well as one social parasite of Acromyrmex: Pseudoatta argentina.Título em inglês: Preliminary study on ants in an oilseed rape plantation, Brassica napus L. (Brassicaceae), at Passo Fundo, Rio Grande do Sul, Brazil

A temporary social parasite of tropical plant-ants improves the fitness of a myrmecophyte

Myrmecophytes offer plant-ants a nesting place in exchange for protection from their enemies, particularly defoliators. These obligate ant-plant mutualisms are common model systems for studying factors that allow horizontally transmitted mutualisms to persist since parasites of ant-myrmecophyte mutualisms exploit the rewards provided by host plants whilst providing no protection in return. In pioneer formations in French Guiana, Azteca alfari and Azteca ovaticeps are known to be mutualists of myrmecophytic Cecropia (Cecropia ants). Here, we show that Azteca andreae, whose colonies build carton nests on myrmecophytic Cecropia, is not a parasite of Azteca-Cecropia mutualisms nor is it a temporary social parasite of A. alfari; it is, however, a temporary social parasite of A. ovaticeps. Contrarily to the two mutualistic Azteca species that are only occasional predators feeding mostly on hemipteran honeydew and food bodies provided by the host trees, A. andreae workers, which also attend hemipterans, do not exploit the food bodies. Rather, they employ an effective hunting technique where the leaf margins are fringed with ambushing workers, waiting for insects to alight. As a result, the host trees' fitness is not affected as A. andreae colonies protect their foliage better than do mutualistic Azteca species resulting in greater fruit production. Yet, contrarily to mutualistic Azteca, when host tree development does not keep pace with colony growth, A. andreae workers forage on surrounding plants; the colonies can even move to a non-Cecropia tree

Inherited biotic protection in a Neotropical pioneer plant

Chelonanthus alatus is a bat-pollinated, pioneer Gentianaceae that clusters in patches where still-standing, dried-out stems are interspersed among live individuals. Flowers bear circum-floral nectaries (CFNs) that are attractive to ants, and seed dispersal is both barochorous and anemochorous. Although, in this study, live individuals never sheltered ant colonies, dried-out hollow stems - that can remain standing for 2 years - did. Workers from species nesting in dried-out stems as well as from ground-nesting species exploited the CFNs of live C. alatus individuals in the same patches during the daytime, but were absent at night (when bat pollination occurs) on 60.5% of the plants. By visiting the CFNs, the ants indirectly protect the flowers - but not the plant foliage - from herbivorous insects. We show that this protection is provided mostly by species nesting in dried-out stems, predominantly Pseudomyrmex gracilis. That dried-out stems remain standing for years and are regularly replaced results in an opportunistic, but stable association where colonies are sheltered by one generation of dead C. alatus while the live individuals nearby, belonging to the next generation, provide them with nectar; in turn, the ants protect their flowers from herbivores. We suggest that the investment in wood by C. alatus individuals permitting stillstanding, dried-out stems to shelter ant colonies constitutes an extended phenotype because foraging workers protect the flowers of live individuals in the same patch. Also, through this process these dried-out stems indirectly favor the reproduction (and so the fitness) of the next generation including both their own offspring and that of their siblings, alladding up to a potential case of inclusive fitness in plants

Fauna de Formicidae capturadas com armadilhas Pitfall em remanescente florestal no município de Plácido de Castro.

As formigas são consideradas um dos grupos de invertebrados mais importantes dos ecossistemas terrestres, participando de importantes processos ecológicos entre animais e plantas, além de serem indicadas como bons organismos de impactos ambientais. Entretanto, a fauna de formigas do estado do Acre ainda é pobremente conhecida. Neste sentido, o objetivo deste trabalho foi realizar um levantamento de formigas utilizando armadilhas do tipo "pitfall trap" em um remanescente florestal localizado no município de Plácido de Castro, AC