Environmental Response of Dinoponera lucida Emery 1901 (Hymenoptera: Formicidae), an Endemic Threatened Species of the Atlantic Forest Central Corridor

Endemic species of Atlantic Forest Central Corridor may have evolved under adverse climate conditions, but their response to modern climate change is unclear. The aim of this study is to evaluate the response of the endemic and endangered ant species Dinoponera lucida to biotics and abiotics factors based on three scales: ecological factors inside forest fragment, physical attributes of landscape and climatic variables of the assessed region. Data collection took place in a representative selection of forest fragments in the region where the species is distributed in. Pitfalls were used to collect samples and to assure the presence and absence of the species in the site. We also checked the abundance of food resources and applied a hemispherical photography technique to measure shading inside the fragment, in loco. Landscape attributes data and climatic predictors were collected through geoprocessing techniques. All predictors were associated with binary “presence” and “absence” data based applied in logistic models. There was no significant response to environmental aspects within the fragment or to landscape, but there was strong and peculiar response to climatic variables such as temperature and rainfall. Accordingly, D. lucida presents a restricted realized niche, a feature shared among many endangered species that can disappear due to displacement and to habitat loss caused by climate and environmental changes. This species presents all the criteria necessary to be considered as rare, which is a controversial subject with political implications for Espírito Santo state, and makes D. lucida the ideal target for urgent conservation strategies

The Influence of Extrafloral Nectaries on Arboreal Ant Species Richness in Tree Communities

Studies investigating the role of resource availability in the species richness patterns can elucidate ecological processes and contribute to conservation strategies. In this study, we test two hypotheses: i) arboreal ant species richness increases with abundance of extrafloral nectaries-bearing trees; and ii) arboreal ant species richness increases with the diversity of extrafloral nectaries-bearing trees. We used data of ant sampling and tree inventories from 30 plots of Brazilian Cerrado. Arboreal ant species richness was positively influenced by the proportional abundance of extrafloral nectaries-bearing trees, total tree density and total tree diversity. There was no effect of species richness of extrafloral nectaries-bearing trees. Coefficient of determination of proportional abundance of extrafloral nectaries-bearing trees was larger when compared to coefficient obtained using tree density as explanatory variable. These results suggest that variation in arboreal ant species richness is better explained by extrafloral nectaries-bearing tree abundance than total tree density. Generalist foraging behavior of sampled ant species may explain their association with proportional abundance of extrafloral nectariesbearing trees and their non-significant relation with proportional richness of extrafloral nectaries-bearing tree species. Extrafloral nectaries-bearing trees abundance may be a specific estimate of the amount of food resource available in plots. Thus, this is a more specific way to quantify which resources may explain variation of the arboreal ant species richness in tree communities. We hope these results will be helpful to understanding the local variation in ant species richness and as criteria to biodiversity conservation

Ant Assemblage Structure in a Secondary Tropical Dry Forest: The Role of Ecological Succession and Seasonality

This study identified the main biological mechanisms governing the diversity of ants on different ecological time scales. Ants were sampled in 15 plots distributed in early, intermediate and late stages of succession (five plots per stage) at the Parque Estadual da Mata Seca, Brazil. At each sample point, unbaited pitfall traps were installed in hypogaeic, epigaeic and arboreal strata. We collected 95 ant species from 26 genera and nine subfamilies. Our results indicated that there was an increase in species richness in advanced stages of succession. We also observed that ant assemblages were different among successional stages. For the arboreal and epigaeic strata, species richness did not change with succession progression, but species composition of these two strata differed among successional stages. Unlike to arboreal and epigaeic ants, hypogaiec ant species richness was higher in the intermediate and late stages of succession and the composition of hypogaeic ants differed among successional stages. Similarity between ant species foraging in arboreal and epigaeic strata decreases with succession progression and β-diversity was higher in advanced successional stages. Additionally, species richness was higher in the dry season, whereas the composition of ant assemblages did not change between seasons. A considerable fraction of the ant assemblage was found only in advanced stages of succession, demonstrating the importance of secondary habitats in maintaining biodiversity in dry forests

A Quantitative Baseline of Ants and Orchid Bees in Human-Modified Amazonian Landscapes in Paragominas, PA, Brazil.

The lack of effective biodiversity baselines is a major impairment to implement conservation plans. Hence, constructing and updating species lists provides vital information about species distribution records. The Sustainable Amazon Network (in Portuguese Rede Amazônia Sustentável; RAS) is an interdisciplinary research initiative that aims to evaluate land-cover changes effects in eastern Brazilian Amazonia. Within the scope of this project, we sampled ants and orchid bees and herein present a list of species collected in Paragominas, PA, Brazil; the most complete lists of species published to date of these groups for the eastern Amazon. We sampled these insects across several land-cover types, from undisturbed primary forest, through varyingly disturbed primary and secondary forests to production areas (silviculture, pastures and arable fields). In total we recorded 285 species of ants and 36 species of orchid bees. Species richness was higher in primary forests for both groups, followed by production areas. Orchid bees reached their highest richness in secondary forests. For orchid bees, production areas were dominated by a few hyper-dominant species, such as Eulaema nigrita. We acknowledge that the use of different sampling methods would collect additional species, and we recommend this for future assessments if the aim is to make a complete inventory. We expect this study can be used as a baseline for understanding the effectiveness of ongoing changes in forest conservation and land management practices. Finally, this list is of suitable importance in determining conservation status for several taxa described here

Divergence of Ant Communities Over Time in a Fragmented Atlantic Rain Forest Landscape

Habitat fragmentation changes biological communities and its spatiotemporal dynamics – which may lead to either biotic homogenization or heterogenization along time and space. Both processes can occur by addition, replacement or loss of species within communities, altering compositional similarity across the landscape. We investigated which of these two processes (biotic homogenization or heterogenization) occurs, and its possible underlying mechanism, over 15 years in an Atlantic Forest landscape using ants as model organisms. We sampled ants in 17 forest fragments across three different years, compared their composition similarity, species richness, and species richness of groups classified according to their habitat preferences. We sampled a total of 132 ant species. Ant communities in fragments diverged over time, suggesting they experienced an idiosyncratic structuring process. This biotic heterogenization occurred through an additive process, as ant species richness increased over time, mainly due to an increase of generalist ant species, and a decrease of forest specialist ant species. These changes occurred despite the higher forest cover in the landscape along years. Since different species can perform different functions in ecosystems, this biotic heterogenization may have implications for ecosystem functioning. Investigating how disturbances structure biological communities over time, especially those performing important ecosystem functions, can shed light to our understanding of possible changes in ecosystem functions and consequently for forest regeneration

Biotic and abiotic factors shaping ant (Hymenoptera: Formicidae) assemblages in brazilian coastal sand dunes: the case of Restinga in Santa Catarina

Species inhabiting Brazilian coastal sand dunes (restingas) may feature a number of adaptations in their development and survival in these physical stressful environments. The present study determined the effect of biotic and abiotic factors on the assemblage of grounddwelling ants in a sand dune ecosystem of the Santa Catarina coastal plain in Brazil. Both linear and quadratic models were significant, but the quadratic model fitted the obtained data better. Furthermore, we also found a relationship between plant species richness and distance from the ocean only by using the quadratic model. Ant species richness was correlated with plant species richness, litter and vegetation coverage. Different environmental factors associated with plant species richness may have influenced the ant species richness by increasing the diversity and amount of available resources. The vegetation may also offer protection from higher temperatures by providing shade, a humid microclimate and a source of water, which is a limiting factor in sand dune environments. Our results showed the importance of plant species richness, and soil cover by litter and plants as local characteristics determining ant species richness in sand dunes. Further studies should explore additional habitat components, such as biotic interactions, as determinants of ant species richness.Espécies que habitam a restinga apresentam adaptações para seu desenvolvimento e sobrevivência sob inúmeros fatores ambientais estressantes. A seleção de um habitat particular deve depender destes diversos componentes do ambiente físico, associado às interações biológicas. O presente estudo foi realizado na restinga herbáceo- arbustiva do Morro dos Conventos para determinar a influência da distância do oceano, fatores bióticos e abióticos sobre a comunidade de formigas de solo. Foram instaladas 65 armadilhas de solo em dois transectos arbitrários de 650 metros a partir do oceano em direção ao continente. Um total de 71 espécies de formigas foi amostrado. Os gêneros Pheidole, Solenopsis e Camponotus foram os gêneros mais representativos. Foi encontrada uma relação positiva entre distância do oceano e riqueza de espécies de formigas, bem como entre distância do oceano e riqueza de espécies de plantas. Das hipóteses testadas, apenas as que estavam relacionadas com a vegetação foram aceitas. A riqueza de espécies de formigas esteve relacionada com a riqueza de espécies de plantas e cobertura do solo. A riqueza de espécies de plantas pode ter influenciado o aumento da riqueza de espécies de formigas pelo aumento da variedade de recursos para consumo e nidificação. Além disso, a vegetação pode alterar as condições microclimáticas, com o aumento da umidade e diminuição da temperatura, fatores extremamente importantes em ambientes com alta incidência de radiação solar e altas taxas e evapotranspiração como a restinga. Esses resultados permitem sugerir a importância da vegetação, e os componentes ligados a ela, como fatores locais determinantes da riqueza de espécies de formigas em Restinga

Small-scale patch dynamics after disturbance in litter ant communities

The dynamics of re-colonisation of disturbed patches may aid in the understanding of spatial variation of species richness. The present study experimentally tested the hypothesis that the variation of litter ant local species richness and composition is caused by the dynamics of re-colonisation after disturbances. We were particularly interested in whether the re-colonisation was by pre-existent species or species new to the patches, and whether the succession of species evidences the existence of dominance-controlled or founder-controlled communities. Litter patches of a forest remnant in Southeast Brazil were disturbed by removing most animals through litter drying, and litter samples were returned to the same sites from where they were removed. Ant species richness and composition were compared before and 2 months after the disturbance. Dissimilarity among disturbed and non-disturbed samples was compared to infer the succession model occurring after disturbance. Ant species richness did not recover after 2 months, and species composition of the disturbed samples showed more new colonisers than pre-existent species. Dissimilarity among samples in the disturbed plots was smaller than in the control plots, indicating a directional, or dominance-controlled, succession. The changes in species composition observed were caused by a decrease of some species, particularly predators, and an increase of species that are possibly opportunistic. Patches of litter are naturally disturbed in time and space, and evidence from the present paper indicates that succession occurring in these patches would lead to different species richness and compositions. Thus the dynamics of re-colonisation contributes to explaining the diversity of litter-dwelling ant communities at larger spatial and temporal scales. In each patch the succession seems to be directional, with opportunist species re-colonising preferentially empty plots. Therefore, these communities may attain a high diversity due to a small-scale patch dynamics model

How pervasive is biotic homogenization in human‐modified tropical forest landscapes?

Land-cover change and ecosystem degradation may lead to biotic homogenization, yet our under- standing of this phenomenon over large spatial scales and different biotic groups remains weak. We used a multi-taxa dataset from 335 sites and 36 heterogeneous landscapes in the Brazilian Amazon to examine the potential for landscape-scale processes to modulate the cumulative effects of local disturbances. Biotic homogenization was high in production areas but much less in disturbed and regenerating forests, where high levels of among-site and among-landscape b-diversity appeared to attenuate species loss at larger scales. We found consistently high levels of b-diversity among landscapes for all land cover classes, providing support for landscape-scale divergence in species composition. Our findings support concerns that b-diversity has been underestimated as a driver of biodiversity change and underscore the importance of maintaining a distributed network of reserves, including remaining areas of undisturbed primary forest, but also disturbed and regenerating forests, to conserve regional biota

Determinação do fator de conversão em colônias de Atta sexdens rubropilosa (Hymenoptera: Formicidae) e sua relação com a qualidade do material vegetal cortado Determination of the conversion factor in colonies of Atta sexdens rubropilosa (Hymenoptera: Formicidae) and its relationship with the quality of harvested leaf substrate

As formigas cortadeiras (Atta e Acromyrmex) são consideradas importantes pragas na agricultura e silvicultura, mas pouco se sabe sobre os reais danos dessas espécies. Uma forma bastante difundida de avaliação do dano é por meio do cálculo da taxa de conversão, dividindo-se o peso do material cortado pelo peso de lixo produzido pelas colônias. Foi levantada a hipótese de que a qualidade do substrato cortado pode influenciar no forrageamento das operárias, alterando a taxa de conversão e dificultando as estimativas de dano. A taxa de conversão de oito colônias de Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae) foi calculada com duas espécies vegetais com diferentes concentrações de lignina e celulose, para testar essa hipótese. Colônias mantidas com folhas de baixa qualidade (razão lignina/celulose elevada) tiveram maior forrageamento e produziram mais lixo. Entretanto, a taxa de conversão das colônias foi semelhante com essas duas plantas (média = 1,54). Esse valor está dentro da variação encontrada para outras espécies no campo (1,5-1,8), indicando um fator semelhante de conversão entre os gêneros Atta e Acromyrmex. O consumo médio de material vegetal, em termos de pesos seco e fresco, de uma colônia de A. sexdens rubropilosa com 4.500 operárias, foi estimado em 520 e 1.100 g/ano, respectivamente.<br>Leaf-cutting ants (Atta and Acromyrmex) are important pests in agriculture and forestry, although few data exist on the actual damage caused by these species. A model used to evaluate damage by leaf-cutting ants are estimates of the conversion factor, which is the ratio between the weight of material cut by the ants and the refuse produced by the colonies. The hypothesis that substrate quality influences foraging by workers, modifying the conversion factor and impairing damage estimates was put forward. To test this hypothesis, the conversion factor was calculated for eight colonies of Atta sexdens rubropilosa Forel (Hymenoptera: Formicidae), using two plant species, with different lignin and cellulose concentrations. Colonies maintained with low quality leaves (high lignin/cellulose ratio) presented higher foraging activity and produced more refuse than colonies maintained with high quality leaves. However, the conversion factors obtained for the two groups of leaf-cutting ant colonies (average = 1.54) was within the variation found for other species in the field (1.5 - 1.8), indicating a similar conversion factor in Atta and Acromyrmex. The average consumption in both dry and fresh weight of plant material of a colony of Atta sexdens rubropilosa with 4,500 workers was estimated as 520 and 1,100 g/year, respectively

ATLANTIC ANTS: a data set of ants in Atlantic Forests of South America

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