Leaf-cutting ants (Atta spp.) have become a topical issue in Neotropical ecology, particularly because they are reaching hyper-abundance due to escalating levels of fragmentation in recent years. Yet, despite intensive research on their role as dominant herbivores, there is still insufficient documentation on the impacts of their large, long-lived nests on plant assemblage structure and ecosystem functioning. Our study aimed at investigating the magnitude, nature, and spatial extent of nest influence by assessing 11 attributes of ant nest, canopy structure, light environment and sapling assemblage for 20 colonies in four plots along nest-understorey gradients in a large remnant of Atlantic forest. We also monitored the performance of seeds and seedlings of Chrysophyllum viride, an abundant shade-tolerant species. Previously unrecognized canopy gaps above ant nests (0.04-87.9 m(2)) occurred in 95% of all colonies surveyed. Overall, canopy openness and light availability at least doubled in ant nest plots compared with distant understorey plots. These drastic changes in the light environment paralleled those in plant assemblage: sapling density almost tripled (mean +/- SE: 0.42 +/- 0.1 saplings m(-2)) and sapling species richness doubled (0.16 +/- 0.02 species m(-2)) in distant plots, as did shade-tolerant species. After a 1-year period, only 33 +/- 15.6% of the seeds germinated and all seedlings died on nests, whereas seed germination reached 68 +/- 5.1% in distant plots and 66.4 +/- 7.6% of their seedlings survived after 12 months. Therefore, plot location was the most significant explanatory variable for predictable and conspicuous changes in the light environment and structure of sapling assemblages. Our findings greatly extend knowledge on the role played by leaf-cutting ants as ecosystem engineers by demonstrating that ant nest-mediated disturbance promotes environmental modifications in tens of meters around nests and is thus, strong enough to drive plant recruitment and consequently alter both the floristic and functional signature of plant assemblages.

-Species richness of epigeic ants was surveyed in forest islands named capões of Brazilian Pantanal and related with their structural complexity. The ants were collected using pitfall traps in 28 capões from Rio Negro Farm, in Aquidauana municipality, Mato-Grosso do Sul state, Brazil. The structural complexity of capões was evaluated by measuring vegetation density and litter quantity near the pit-fall traps. Seventy-one species, distributed in 26 genera and seven sub-families were found. Ectatomma edentatum Roger (Formicidae: Ectatomminae) and one species of Pheidole were the most frequent species. Species richness was positively correlated only with herbaceous vegetation density of capões, supporting the idea that the increase in environmental heterogeneity diminishes species competition, allowing species co-occurrence.KEY WORDS: Insecta, litter, pitfall trap RESUMO -A riqueza de formigas de capões do Pantanal brasileiro foi amostrada e relacionada com a complexidade estrutural das áreas. As formigas foram coletadas com armadilhas de solo do tipo pitfall em 28 capões na Fazenda Rio Negro, Município de Aquidauana, MS. A complexidade estrutural dos capões foi avaliada através de estimativa da densidade da vegetação e da espessura da serapilheira próximo às armadilhas. Setenta e uma espécies foram encontradas, pertencentes a 26 gêneros e sete subfamílias, das quais Ectatomma edentatum Roger (Formicidae: Ectatomminae) e uma espécie de Pheidole foram as mais freqüentes. Somente foi encontrada relação positiva entre a riqueza da comunidade de formigas e a densidade da vegetação herbácea, corroborando a idéia de que a heterogeneidade do ambiente é um fator determinante para a coexistência e diminuição de competição entre espécies.PALAVRAS-CHAVE -Insecta, armadilha pitfall, serapilheira O Pantanal Mato-Grossense, considerado uma das maiores planícies de inundação da América Latina, com cerca de 140.000 km² (Brasil 1982), é um mosaico de comunidades, com mudanças abruptas na paisagem (Prance & Schaller 1982), resultado da interação entre fatores edáfi cos, hidrológicos e biogeográfi cos (Lourival et al. 2000). Apresenta diversos tipos fi sionômicos, dentre eles os capões, que são grandes montes de terra, cobertos por vegetação com formato circular ou elíptico e esparsamente distribuídos em campos sujeitos à inundação sazonal (Ponce & Cunha 1993). Suas bordas são constituídas de espécies vegetais típicas de mata ciliar e savanas inundáveis, enquanto a parte central, quase nunca inundável, possui espécies características de mata semi-decídua (Damasceno et al. 1996). O dossel varia de 10-15 m, sendo descontínuo na parte central e fechado em sua periferia (Damasceno et al. 1996). Como estão alojados em uma depressão sedimentar, representam verdadeiras ilhas durante as inundações anuais, o que permite sua colonização por espécies vegetais e animais (Oliveira-Filho 1992). Embora diversos projetos estejam em andamento na região pantaneira, até o momento existem poucas publicações sobre as comunidades de artrópodes no...

Neotropical Entomology 34(4): 695-698 (2005) Ocorrência de Atta cephalotes (L.) (Hymenoptera: Formicidae) em Alagoas RESUMO -Atta cephalotes (L.) apresenta ampla distribuição na região Neotropical. No Brasil, foi registrada na região Amazônica e nos estados do Maranhão, Pernambuco e sul da Bahia, todos pertencentes à Região Nordeste. Neste trabalho é apresentado o registro de A. cephalotes em 42 remanescentes de Floresta Atlântica nordestina em Alagoas e Pernambuco. Os resultados incluem novos registros de A. cephalotes em Alagoas, ampliando a distribuição da espécie no Nordeste. Além disso, mostram que a espécie é fortemente associada a remanescentes de floresta bem conservados, indicando alta sensitividade a perturbações. É sugerido que, no cenário fragmentado da Floresta Atlântica nordestina, A. cephalotes pode estar sendo substituída por A. sexdens que esteve presente em todas as áreas amostradas.

1. Leaf‐cutting ants (LCAs) have often been denoted as ecosystem engineers because of their multifarious effects on the vegetation, particularly via nest‐driven environmental changes. However, the non‐trophic impacts of LCAs on forest dynamics via foliage harvesting across sizeable foraging zones (so‐called associated ecosystem engineering) are still poorly investigated. 2. Here, light availability and sapling assemblages were assessed within foraging areas and ant‐free control zones of 16 Atta cephalotes colonies located in a large remnant of Atlantic forest in northeastern Brazil. 3. Canopy openness and total light transmission were 1.4 and 1.6 times higher in foraging zones than in control areas. In parallel, sapling density and species richness decreased constantly from control to foraging zone plots. Additionally, shade‐tolerant species exhibited reduced abundance across foraging zones. A non‐metric multidimensional scaling ordination based on taxonomic similarity primarily segregated foraging zone and control plots; foraging zone plots converged to be more similar to each other as well. Finally, some plant species emerged as indicators of LCA‐free zones. 4. These results suggest that LCA foraging activity in the forest canopy directly increases the light availability and indirectly affects the recruitment and the structure of local plant assemblages. 5. Such a biologically significant effect on the light environment and its cascades confirms LCAs as potent ecosystem engineers, particularly as a plant assembly force, which operates beyond the spatial reach of their well‐described nest effects.

EntomoBrasilis 8 (2): 85-90 (2015) FórumResumo. Uma associação bem conhecida dentre as interações ecológicas é o mutualismo entre plantas do gênero Cecropia e formigas, na maioria das vezes pertencentes ao gênero Azteca. Nesta interação, as formigas nidificam nas domáceas presentes no tronco oco das mirmecófitas e se alimentam de recursos alimentares fornecidos pela planta, conhecidos como corpúsculos mullerianos. Em compensação, as formigas protegem a planta hospedeira contra o ataque de herbívoros e a invasão por trepadeiras, e nutrem-na através de resíduos abandonados no tronco. Entretanto, a efetividade desta associação pode variar em função de vários fatores, como por exemplo, a espécie de formiga associada e o tipo de habitat da planta mirmecófita. Cerca de 10% das espécies de Cecropia perderam suas características atrativas, como por exemplo, espécies que habitam ilhas e altas altitudes. Aspectos como a riqueza de formigas associadas e estudos moleculares evidenciam que a colonização destas plantas ocorreu diversas vezes e independentemente por alguns gêneros de formigas. A pressão de seleção exercida por algumas espécies de formigas pode ter sido um dos fatores decisivos para o desenvolvimento dos traços atrativos para as formigas em Cecropia. Com a evolução destas características as formigas puderam se tornar um parceiro efetivo da planta, facilitando a co-evolução de interações mais específicas. Palavras-chave:Associação; Benefícios; Co-evolução; Formigas; Mirmecófita. Plant-Insect Interactions: Biological and Ecological Aspects of Cecropia-Azteca MutualismAbstract. A well-known association is the mutualism between plants is between plant species of the genus Cecropia and ants, mostly belonging to the genus Azteca. In this association, the ants nest in domatia present in the hollow trunk of this myrmecophytes and feed on food bodies provided by the plant, known as mullerian bodies. In return, the ants protect the host plant against herbivore attacks and invasion by vines, and nourish it through waste laid in the trunk. However, the effectiveness of this association may vary with several factors, such as the associated ant species and the habitat type of the myrmecophyte. About 10% of Cecropia species lost their attractive characteristics, such as species living in high altitude and inhabit islands. Aspects like associated ant richness and molecular studies show that the colonization of these plants by ants occurred several times and independently by different genera. The selection pressure exerted by some species of ants may have been one of the decisive factors for the development of attractive traits for ants in Cecropia. With the evolution of these features ants might become an effective partner of the plant, facilitating the co-evolution of specific interactions.

Although the interactions (including mutualism) between Cecropia and numerous ants have been already well documented, biogeographic studies on the distribution patterns of Cecropia with its associated ants have never been conducted in northeast Brazil. This study evaluates: (1) the regional diversity of Cecropia spp. sheltering ants; (2) the diversity of the ants living in these trees; and (3) the species-specific relationships along a longitudinal east-west transect in southwest Bahia. The ants nesting at the apical stem of 521 Cecropia individuals, mostly C. pachystachya (Trécul 1847), were sampled; 437 trees were occupied by ants belonging to 40 species. The commonest ant species was Azteca alfari (Emery 1893). The abundance of Cecropia, as well as the relative frequency of tree occupation, ant diversity, and association between ant species, were higher at lower altitudes, where rainforest vegetation predominates. Cecropia proved to be an important nesting site for various ant species in this biotope.Résumé. Interactions entre Cecropia (Urticaceae) et les fourmis (Hymenoptera : Formicidae) le long d'un transect longitudinal est-ouest dans le Nord-est du Brésil. Bien que les interactions (dont le mutualisme) entre Cecropia et de nombreuses fourmis aient déjà été bien documentées, aucune étude biogéographique portant sur les modèles de distribution de Cecropia et de ses fourmis associées n'a été menée jusqu'à présent dans le Nord-Est du Brésil. Cette étude évalue : 1) la diversité régionale de Cecropia spp. abritant des fourmis ; 2) la diversité des fourmis qui vivent dans ces arbres ; et 3) la relation de spécificité qui existe dans ces relations le long d'un transect longitudal est-ouest situé dans le sud de Bahia (Brésil). Nous avons échantillonné les fourmis des rameaux apicaux de 521 Cecropia, principalement C. pachystachya (Trécul 1847); 437 arbres étaient occupés par 40 espèces de fourmis. La fourmi la plus fréquente était Azteca alfari (Emery 1893). L'abondance de Cecropia, ainsi que la fréquence relative de l'occupation de l'arbre, la diversité des fourmis et les associations entre espèces de fourmis, étaient plus élevées à basse altitude où la végétation prédominante est du type forêt tropicale. Cecropia est donc un important site de nidification pour de nombreuses espèces de fourmis dans ce biotope.

Studies on the survival of species are essential to understanding their biology and to developing effective conservation and management plans. This study aimed to determine the best model to explain the survival of the species Melocactus conoideus on the basis of time, density, age structure and habitat location, as well as to describe the interactions among those factors. The study was conducted in three M. conoideus habitat patches in the municipality of Vitória da Conquista, in the state of Bahia, Brazil, only one of which was within a "conservation unit" (protected area). In each patch, we selected 120 specimens of M. conoideus, which were marked with identification plates and classified by developmental stage and density. The survival of those individuals was monitored for a period of one year. The overall survival of M. conoideus was 87.5% and was found to correlate with the month, as well as with the interaction between the factors Patch and Density. Our results show that the survival of M. conoideus individuals is related to the intrinsic characteristics of each habitat patch and suggest that more areas should be set aside for the conservation of this species.

-(Tree heterogeneity and diversity in cabrucas in central South of Bahia State, Brazil). The contribution of managed ecosystems for biodiversity conservation has been highlighted by recent studies. Tree species diversity was investigated in Cabruca (a traditional agroforest with cocoa and native trees) of ten cocoa farms in central-Southern Bahia state to quantify the remnant tree diversity and to verify if it is influenced by the size of the farm and the size of the Cabruca. A total of 273 trees, 55 trees species and 20 plant families were recorded. From these, 89% of plant species and 73% of trees were native species. In average, 23 to 60 tree species and 40 to 236 individuals per hectare were registered. The Shannon-Wiener (H') index varied from 1.3 to 2.5. The mixture coefficient of Jentsch (QM) obtained was two individuals per species. A high heterogeneity was observed among the Cabrucas studied. Tree diversity was not correlated, however, with the total area of the farms or the area of Cabruca on the farms. Our results indicate that Cabruca are variable in tree density and diversity. Additionally, management performed by cocoa farm owners is the main factor that influences the tree community attributes in this agroforestry. Keywords: Agroforestry systems, Atlantic forest, cocoa tree, managed ecosystem, native species RESUMO -(Heterogeneidade na estrutura e diversidade de árvores de cabrucas no centro-sul do Estado da Bahia, Brasil). O objetivo deste trabalho foi conhecer a diversidade arbórea de cabrucas de fazendas produtoras de cacau no centro-sul da Bahia e verificar se fatores como as áreas das propriedades e das cabrucas influenciam as comunidades arbóreas remanescentes. Foram encontrados 273 indivíduos, pertencentes a 55 espécies e 20 famílias, sendo que 89% das espécies e 73% dos indivíduos são nativos da região. Em média, por hectare, foram registrados 23 a 60 espécies arbóreas e 40 a 236 indivíduos. O índice de Shannon-Wiener (H') variou de 1,3 a 2,5 e o quociente de mistura de Jenstch resultou em uma proporção de dois indivíduos para cada espécie. As cabrucas estudadas apresentaram alta heterogeneidade. Contudo, a diversidade arbórea não foi correlacionada com a área total e nem com a área de cabruca nas propriedades. Nossos resultados indicam que as cabrucas são muito variáveis em densidade e diversidade e que o sistema de manejo realizado pelos proprietários das fazendas parece ser o fator que mais influencia os atributos da comunidade arbórea nestas agroflorestas.