Navegando por Autor "Fagundes, Roberth"
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Item Análise preliminar de mosaico de formigas arbóreas : métodos comparativos para a investigação de insetos de dossel - MG.(2011) Silva, Glênia Lourenço; Maia, Ana Carolina Resende; Espírito Santo, Nádia Barbosa do; Fagundes, Roberth; Costa, Cinthia Borges da; Ribeiro, Sérvio PontesA diversidade de espécies de insetos nas florestas tropicais varia em resposta a diversos fatores. Nas copas das árvores das florestas tropicais as formigas talvez sejam os predadores ecologicamente mais importantes. O objetivo deste trabalho foi comparar a distribuição de riqueza e abundância de insetos entre fisionomias florestais distintas, utilizando duas metodologias de amostragem, no Parque Estadual do Itacolomi. As coletas foram feitas pelos métodos de pitfall arbóreo e de batimento com guarda-chuva entomológico em áreas de estágio sucessional inicial, intermediário e tardio. Os métodos apresentaram diferença na captura de insetos quanto à abundância.Item O bambu Merostachys fischeriana (Bambusoideae: Bambuseae) como habitat para formigas de floresta tropical montana.(2010) Fagundes, Roberth; Terra, Gilberto; Ribeiro, Sérvio Pontes; Majer, Jonathan DavidAlthough Merostachys fi scheriana is very abundant in the Brazilian Atlantic Rainforest, little attention has been paid to the biological interactions with other animals. The present study describes some of the interactions between ants and this bamboo species. The experiment was carried out in a fragment of a montane tropical forest in the Parque Estadual do Itacolomi, near Ouro Preto, MG, Brazil. Thirty culms of bamboo were randomly collected. The ants were obtained by direct collection from nodes and internodes. Morphometric variables of the bamboo were recorded for characterization of potential ant habitat. Merostachys fi scheriana grows in rosettes as a thin bamboo (average = 1,0 cm; se = 0,27; n = 20) and is tall enough to reach the upper canopy of this low forest (average = 9,1 m; se = 2,72; n = 20). Fifteen ant species were sampled. Brachymyrmex heeri Forel was the most abundant in the nodes, while Camponotus crassus Mayr (Hymenoptera: Formicidae) was the most abundant in the internodes. The composition of the species that inhabit the internodes was different from the composition in the node (Q-test: Q = 3,76; P = 0,05). The level of occupation was defi ned by the number of holes (F = 10,33; P < 0,01), the number of internodes in the canopy (F = 6,84; P = 0,01) and the length of the culm (F = 7,52; P = 0,01). The plant’s morphology allowed the occurrence of additional species of ants in the canopy and infl uenced the composition of the entire ant assemblage.Item Cornfield effects on breeding and abundance of Oligoryzomys nigripes (Rodentia: Sigmodontinae).(2020) Braga, Caryne Aparecida de Carvalho; Oliveira, Gisela Barbosa Sobral de; Zeppelini, Caio Graco; Fagundes, Roberth; Pires, Maria Rita SilvérioSmall rodents rely on resource gathering during the breeding season to support their reproductive output and o spring survival. Since croplands may provide complementary food sources, we evaluated the in uence of the presence of corn eld on the forest edge in Oligoryzomys nigripes (Olfers, 1818) abundance and breeding. We found that abundance, proportion of reproductive females and males, as well as the number of juveniles were higher in the corn eld-forest edges, with no seasonality, a pattern divergent from the seasonal reproduction described for the species. Therefore, our results supported the hypothesis of corn elds bene ting O. nigripes abundance and breeding success.Item Dinâmica das comunidades de formigas em um ecossistema tropical montano em áreas com e sem perturbação por fogo.(2015) Silva, Diego Vinícius Anjos; Ribeiro, Sérvio Pontes; Fagundes, Roberth; Ribeiro, Sérvio Pontes; Campos, Ricardo Ildefonso de; Milanez, Cinthia Borges da CostaPertubações antrópicas, principalmente o fogo, causam importantes modificações nos habitats e nas comunidades que neles vivem. O objetivo deste estudo foi monitorar a sucessão natural das assembleias de formigas em áreas perturbadas ou não pelo fogo, num ecossistema Tropical Montano. Dessa maneira, amostragens mensais da mirmecofauna ocorreram em quatro distintas áreas ao longo de dois anos no Parque Estadual do Itacolomi, MG, Brasil. Testamos a hipótese de que o fogo afeta diferentemente as assembléias de formigas no solo e na vegetação. Também foi testada a hipótese de que a recuperação, sucessão natural, da mirmecofauna ocorre de maneira direcional. Encontramos diferenças nas respostas das formigas que vivem no solo em relação as que vivem na vegetação. Ao contrário do esperado, a assembléia de formigas na vegetação se recuperou mais rapidamente que a assembléia no solo. Embora a sucessão ocorreu mais evidentemente nas áreas queimadas quando comparado às áreas não queimadas, a sucessão não foi direcional. Isto se deve principalmente às diferenças importantes na composição de espécies. Estudos como esse reforçam a importância de se entender as consequências das queimadas nas comunidades de insetos e a relevância do entendimento do fogo na conservação dos ecossistemas Tropicais Montanos.Item Evidences that human disturbance simplify the ant fauna associated a Stachytarpheta glabra Cham. (Verbenaceae) compromising the benefits of ant-plant mutualism.(2015) Barbosa, Bárbara de Carvalho; Fagundes, Roberth; Silva, L. F.; Tofoli, J. F. V.; Santos, A. M.; Imai, B. Y. P.; Gomes, Gabriel Guimarães; Hermidorff, Milla Marques; Ribeiro, Sérvio PontesAs interações entre espécies, como por exemplo formigas e plantas através de nectários extraflorais (NEFs), são importantes componentes na evolução das comunidades. Entretanto, pouco é conhecido sobre os efeitos dos impactos antrópicos em interações específicas e suas consequências ecológicas. Este estudo avaliou os resultados do mutualismo entre formigas e NEF em Stachytarpheta glabra em área impactada pela atividade humana. Nós comparamos a composição e estrutura da fauna de artrópodes, em quarenta plantas de dois grupos, um impactado por atividades humanas e o outro preservado. Nós também avaliamos o investimento da planta em defesas contra herbívoros e os danos foliares causados por herbívoros. Nossos resultados indicam que os distúrbios causam a simplificação da fauna associada e a ausência de uma formiga mutualista anti-herbívoros. Isto leva a quatro vezes mais herbivoria nas plantas da área impactada, a despeito da mesma quantidade encontrada para NEF e formigas visitantes. A grande pressão de herbivoria pode dificultar o reestabelecimento de S. glabra, uma espécie pioneira importante nos campos ferruginosos, dessa forma, afetando a resiliência dessa comunidade ecológica ameaçada.Item Extrafloral-nectaries and interspecific aggressiveness regulate day/night turnover of ant species foraging for nectar on Bionia coriacea.(2016) Silva, Diego Vinícius Anjos; Caserio, Barbara Machado; Rezende, Felipe Teles; Ribeiro, Sérvio Pontes; Claro, Kleber Del; Fagundes, RoberthPlants bearing extrafloral nectaries (EFNs) vary the secretion of nectar between day and night, which creates turnover in the composition of interacting ant species. Daily variation in the composition of ant species foraging on vegetation is commonly observed, but its mechanisms are poorly understood. We evaluated the daily variation in nectar availability and interspecific aggressiveness between ants as possible regulatory mechanisms of the turnover in ant–plant interactions. We hypothesized that (i) plants would interact with more ant species during periods of higher secretion of nectar and that (ii) aggressive ant species would compete for nectar, creating a daily turnover of species collecting nectar. We tested this hypothesis by measuring the production of nectar during the day and night and by experimentally removing EFNs of Bionia coriacea (=Camptosema coriaceum) (Nees & Mart.) Benth. (Fabaceae: Faboideae) plants in a Brazilian savanna (Cerrado). We then compared the abundance and composition of ant species between those treatments and during the day. Our results indicate that more ant workers forage on plants during the day, when nectar was sugary, while more ant species forage at night, when aggressiveness between ant species was lower. We also detected a day/night turnover in ant species composition. Ant species foraging for nectar during the day were not the same at night, and this turnover did not occur on plants without EFNs. Both dominant ant species, diurnal Camponotus crassus (Hymenoptera: Formicidae) and nocturnal Camponotus rufipes (Hymenoptera: Formicidae), were the most aggressive species, attacking other ants in their specific periods of forage while also being very aggressive toward each other. However, this aggressiveness did not occur in the absence of nectar, which allowed non-aggressive nocturnal ant species to forage only during the daytime, disrupting the turnover. We conclude that extrafloral-nectar presence and interspecific aggressiveness between ants, along with other environmental factors, are important mechanisms creating turnovers in ants foraging on plants.Item Food source availability and interspecific dominance as structural mechanisms of ant-plant-hemipteran multitrophic networks.(2016) Fagundes, Roberth; Cruz, Wesley Francisco Dáttilo da; Ribeiro, Sérvio Pontes; Gray, Victor Rico; Claro, Kleber DelExtrafloral nectar of plants and honeydew of hemipterans is a food source extensively explored by ants. Although basically a sugary liquid food, nectar and honeydew are composed of different nutrients and offered in distinct ways; thus, ants must interact differently with plants and hemipterans. In this study we assessed the availability and dominance of nectar of extrafloral nectaries and honeydew of sap-sucking hemipterans (i.e., sugarbased resources) as mechanisms regulating interaction frequency and structuring ant-plant-hemipteran networks. We studied 12 plant species (240 shrubs, 20 per species) and 12 hemipteran species (240 aggregations, 20 per species) that interacted with 26 ant species in an area of Rupestrian Fields (Rocky Montane Savannah), Brazil. We observed that the 7 ant species that collected honeydew were a subset of the 25 ant species feeding on nectar, but the highly interacted species Camponotus crassus was the same for both subnetworks. The ant-plant subnetwork exhibited a nested pattern of interaction with a low degree of specialization, while the ant-hemipteran subnetwork exhibited lower nestedness but higher specialization. We found a positive relationship between the offer of EFNs and the number of interactions with ants, probably resulting from reduced competition in plants with high availability of EFNs. However, hemipteran species that were most abundant did not interact with more species of ants, probably because of the numerical dominance of the species tending all hemipteran aggregations, regardless of size. However, segregation between ant species was higher than expected by chance for both plants and hemipterans, con- firming a deterministic factor (i.e., competition between ant species) regulating the frequency of interactions. In summary, the availability of ENFs seems to be an important mechanism regulating ant-plant interactions, while numerical dominance seems to be an important mechanism structuring ant-hemipteran interactions.Item Limited effects of fire disturbances on the species diversity and structure of ant-plant interaction networks in Brazilian Cerrado.(2018) Fagundes, Roberth; Lange, Denise; Silva, Diego Vinícius Anjos; Lima, Filipe Paixão de; Oliveira, Larissa Nahas Domingues de; Corro, Erick J.; Silva, Pricila Bonifácio Gomes; Claro, Kleber Del; Ribeiro, Sérvio Pontes; Cruz, Wesley Francisco Dáttilo daFire is one of the main natural disturbances in Tropical Savannas, changing the diversity of species, altering the structure of species interactions, and driving the evolution of adaptations. Here, we investigated the effects of fire disturbance on interactions between ants and plants with extrafloral nectaries in Cerrado (Brazilian Savanna). We carried out the study in two different ecosystems of Brazilian Cerrado 700 km apart; Woody Cerrado and Rupestrian Grasslands. We conducted a Before-After-Control-Impact (BACI) experiment, in which the impact was the disturbance caused by fire. In Woody Cerrado, we found no evidence of fire affecting the diversity and composition of plants or its interactions. Fire also did not affect ant diversity but changed the interaction pattern of its interactions by reorganizing the paired interactions between species (i.e., rewiring). However, this effect did not result in changes on the overall structure of the network. In Rupestrian Grasslands, fire also did not affect the diversity and composition of plant species or its interactions, but it did increase the number of ant species and change its composition, leading to a reorganization of the its paired interactions. However, these fire disturbances in the ant level did not affect the overall structure of the network. Our findings indicate that the structure of ant-plant interaction networks is robust to fire disturbances, more in Woody Cerrado than Rupestrian Grasslands, confirming our hypothesis that ant-plant interactions in Cerrado are adapted to fire disturbances. In sum, our study enhances the understanding of the effects of environmental disturbances and the stability of the ant-plant interactions in fire-adapted ecosystems such as Brazilian Cerrado.Item Overlap in cave usage and period of activity as factors structuring the interactions between bats and ectoparasites.(2017) Fagundes, Roberth; Itabaiana, Yasmine Antonini; Aguiar, Ludmilla Moura de SouzaBats perform important ecosystem services such as pollination and seed dispersal. Bats are also hosts to obligate ectoparasites, which influence their behavior and, thus, compromise their ecosystem functions. Therefore, the study of the bat-ectoparasitic interaction network and its driven factors is basic for understanding variation in the ecosystem services provided by bats. In this study, we evaluated the structure of the network of interactions between bats and their ectoparasite arthropods, testing the roles of overlap in cave usage and period of activity as factors structuring the interactions. We conducted the study in caves within the Cerrado ecosystem near Brasília, Brazil. Our results show that the bat-ectoparasite network has a modular pattern and is highly specialized. The observed pattern was explained by the greater probability of transmission of ectoparasites among bats sharing the same cave during the same period of the year. Furthermore, our data showed that the rate of bat infestation by different ectoparasite species is related to the degree of exposure of bats according to their abundance and activity period, but not with the number of caves used to roost. Thus, we believe that the frequency of activity and encounters between bats, and therefore the rate of ectoparasite transmission, is an important regulatory mechanism of bat-ectoparasite networks. This ecological mechanism may facilitate the formation of specific interactions by spatial and temporal segregation and co-evolution of parasite species among groups of roosting bats.Item Recruitment and entropy decrease during trail formation by foraging ants.(2020) Lourenço, Giselle Martins; Ferreira, Fabíola Keesen; Fagundes, Roberth; Luna, P.; Silva, Alcides Volpato Carneiro de Castro e; Ribeiro, Sérvio Pontes; Arashiro, EveraldoSocial insects utilise a complex spatial orientation system mediated by chemical signals. This study investigated how the foraging behaviour of ants (Dorymyrmex thoracicus) varies depending on the quantity of an available resource using a feld experiment. Further, we demonstrated computationally that ant displacement is compatible with a model based on pheromone deposition. Our experiment tested how the resource size (large or small) and availability (one or two simultaneous patches) of resources ofered infuence the number of recruited ants (trafc fow) and the speed of trafc fow both moving towards a resource and returning to the colony. The results showed that the returning fow was higher than the going fow independent of resource. The trafc fow towards a single resource was higher than the fow for either of two simultaneous resources patches ofered; thus, multiple resources sources split the fow, regardless of the fact that resource size did not afect foraging choices. Our results indicated that the ants used an orientation mechanism that can be reproduced by a theoretical computer model. With our model, we showed that initially, the displacement of ants followed no clearly detectable pattern. However, with increasing levels of ant recruitment and consequent pheromone deposition on the most used trails, returning displacement revealed the formation of shorter and more organised trails. The model revealed key transition between periods of order and disorder that continued until the fow of information reached an organised state (Shannon entropy). This study highlights an exceptional mechanism of foraging optimisation in eusocial insects.Item Similar topologies of individual-based plant-herbivorous networks in forest interior and anthropogenic edges.(2021) Carvalho, Raquel Luiza de; Silva, Diego Vinícius Anjos; Fagundes, Roberth; Luna, Pedro; Ribeiro, Sérvio PontesUnderstanding the impacts of edge effects on ecological interactions plays an integral role in planning ecosystem recovery from human perturbations, as well as conservation of habitats. Edge effects related to forest fragmentation cause changes in species diversity that can disrupt ecological networks. Here, we evaluated how the diversity of, and interactions between, herbivorous insects associated with individuals of a pioneer plant species, Mabea fistulifera (Euphorbiaceae) are affected by the disturbances related to edge effects. We addressed two specific questions: (i) How do the forest edges affect species richness, abundance and composition of herbivorous interacting with M. fistulifera? (ii) Do different disturbances related to edge effects affect the topology of individual-based plant-herbivorous networks? Herbivorous insects were sampled from three population patches of M. fistulifera in Brazilian Atlantic forest areas: two areas were subjected to distinct intensities of anthropogenic disturbances (firebreak and park access road, considered edges of low- and high-impact, respectively), and one in the forest interior (control). We expected a lower species richness and abundance of herbivorous interacting with plants in forest edges than in the forest interior apart from to differences in the species composition. Therefore, based on these predictions, we expected that the various disturbances related to edge effects may change the topology of individual-based plant-herbivorous networks. We observed that species richness and abundance of herbivorous in high-impact environments decreased in relation to forest interior, as well the species composition differed between these areas. Disturbance jeopardised network specialisation but did not change the topology of individual-based networks, which presented a modular pattern. Edges affected herbivorous diversity and decreased the interaction overlap as individual-based networks became highly specialised with increasing disturbance. These results enhance the understanding of edge effects and resilience of plant-herbivorous interactions in regularly disturbed tropical environments.Item Trap-nesting hymenoptera and their network with parasites in recovered riparian forests Brazil.(2017) Araújo, Gustavo Júnior de; Fagundes, Roberth; Itabaiana, Yasmine AntoniniDifferent aspects of human activities can cause environmental change that endanger species persistence, alter species distributions, and lead to changes in antagonistic and mutualistic interactions, whereas deforestation and flooding of riparian forest results in landscapes consisting of patchily distributed riparian forest fragments in a matrix of pastures, plantations, and urban areas. Therefore, we assessed the richness, abundance, and trophic interactions of trap-nesting Hymenoptera and their parasites at four patches of restored riparian forest and at one reference natural fragment, of different sizes and ages, located at the Volta Grande Reservoir, in Minas Gerais and São Paulo states to answer the following questions: (1) Does the richness and abundance of cavity-nesting bees and wasps differ in riparian forest fragments according to the seasonal periods? (2) Does the composition of cavity-nesting bees and wasps vary among restoration and reference sites and between climate seasons (wet and dry)? (3) How do the degrees of specialization of the parasites vary among the patches of forest? We recorded 12 species of wasps, eight of bees, and nine species of parasites. Areas with longer time since restoration (reference site) showed higher species richness. However, the abundance was higher in most recent areas. The composition of bee and wasp assembly has not significantly changed between the climate seasons, although it is different between sampling areas. The richness and abundance were higher in warmer and rainy periods. The rate of bee and wasp mortality was high. The degree of specialization of parasites varies among sampling units, and the network of host-parasite interaction has a modular configuration with generalists and specialists. We concluded that the restored areas with more complex habitat could provide better conditions for the reestablishment of ecological interactions among these insects, the local flora, and other invertebrates, which together contribute to the success of the restored environments.