ABSTRACT
The Cerrado confronts threats such as fire and frost due to natural or human-induced factors. These disturbances trigger attribute changes that impact biodiversity. Given escalating climate extremes, understanding the effects of these phenomena on ecological relationships is crucial for biodiversity conservation. To understand how fire and frost affect interactions and influence biological communities in the Cerrado, our study aimed to comprehend the effects of these two disturbances on extrafloral nectar (EFN)-bearing plants (Ouratea spectabilis, Ochnaceae) and their interactions. Our main hypothesis was that plants affected by fire would grow again more quickly than those affected only by frost due to the better adaptation of Cerrado flora to fire. The results showed that fire accelerated the regrowth of O. spectabilis. Regrowth in plants with EFNs attracted ants that proved to be efficient in removing herbivores, significantly reducing foliar herbivory rates in this species, when compared to the species without EFNs, or when ant access was prevented through experimental manipulation. Post-disturbance ant and herbivore populations were low, with frost leading to greater reductions. Ant richness and diversity are higher where frost precedes fire, suggesting that fire restores Cerrado ecological interactions better than frost, with less impact on plants, ants, and herbivores.
ABSTRACT
Few studies have explored the phenotypic plasticity of nectar production on plant attractiveness to ants. Here, we investigate the role of extrafloral nectary (EFN) size on the productivity of extrafloral nectar in three sympatric legume species. We hypothesized that plant species with larger EFNs (i) have higher induced nectar secretion after herbivory events, and (ii) are more likely to interact with more protective (i.e. dominant) ant partners. We target 90 plants of three Chamaecrista species in the field. We estimated EFN size and conducted field experiments to evaluate any differences in nectar traits before and after leaf damage to investigate the phenotypic plasticity of nectar production across species. We conducted multiple censuses of ant species feeding on EFNs over time. Plant species increased nectar descriptors after leaf damage, but in different ways. Supporting our hypothesis, C. duckeana, with the largest EFN size, increased all nectar descriptors, with most intense post-herbivory-induced response, taking its place as the most attractive to ants, including dominant species. EFN size variation was an excellent indicator of nectar productivity across species. The higher control over reward production in plants with larger sized EFNs reflects an induction mechanism under damage that reduces costs and increases the potential benefits of indirect biotic defences.
Subject(s)
Ants , Animals , Ants/physiology , Plant Nectar , Symbiosis , Herbivory/physiology , Plant Leaves/physiology , PlantsABSTRACT
ABSTRACT Most of the ants that are associated with plants usually nests in vegetative organs such as stems, leaves or petioles. Aiming to contribute to the plant-insect interactions, we report the first record of Crematogaster carinata nesting inside the fruits ofMacropsychanthus comosus. We did fieldwork in two localities of department of Antioquia and one of the Bolivar department, we opened 32 pods and determined the insects inside them. We found Crematogaster carinata and a beetle (Coleoptera: Chrysomelidae: Bruchinae) inside. 15 of the 32 pods had ants (47 %), but only seven of them had queens (22 %). The ants left the falling pods. The beetle larvae drilled 15 seeds (14 %). This report points the importance of the research in legume-insect interactions, ant-behavior, trophic webs, and trade-off relationships research.
RESUMEN Las hormigas que se asocian con plantas suelen nidificar en órganos vegetativos como tallos, hojas o pecíolos. Con el propósito de contribuir al conocimiento de las interacciones planta-insecto, reportamos el primer registro de Crematogaster carinata nidificando dentro de los frutos de Macropsychanthus comosus. Realizamos salidas de campo en dos localidades del departamento Antioquia y una del departamento de Bolívar. Abrimos 32 frutos de M. comosus y determinamos los insectos que se encontraban dentro de estos. Encontramos a Crematogaster carinata y a un escarabajo (Coleoptera: Chrysomelidae: Bruchinae). 15 de las 32 legumbres abiertas presentaban hormigas (47 %), pero solo siete de ellas incluyeron reinas (22 %). Los frutos que se desprendieron fueron abandonados por las hormigas. 15 semillas fueron perforadas por las larvas del escarabajo (14 %). Este reporte señala la importancia de la investigación entre interacciones leguminosa-insecto, comportamiento de hormigas, redes tróficas y relaciones de costo-beneficio.
ABSTRACT
Abstract: Pteridium is a cosmopolitan genus of ferns that possess nectaries on its fronds (fern leaves), thereby attracting ants. Foliar (or extrafloral) nectaries are nectar-producing glands that are not related to pollination, but rather attract ants and other arthropods. Foliar nectaries are found in 101 fern species, belonging to 11 genera and six families. The aim of the study is to characterize the community of ants that visit the fronds of Pteridium esculentum subsp. arachnoideum, as well as daily and seasonal ant abundance in different frond development stages. The study was conducted in the Atlantic Forest of Rio de Janeiro state, Brazil. Bimonthly collections were established, where 30 expanding fronds and 30 fully expanded fronds were randomly marked. In each 1-hour shift starting at 8:30 am and ending at 5:30 pm, the fronds were observed for the presence of ants. Thirty three ant species were recorded on the Pteridium esculentum subsp. arachnoideum fronds, distributed into six subfamilies and 13 genera. The most abundant species were Solenopsis sp.1 and Ectatomma tuberculatum. Eight ant species were observed foraging the nectaries of tropical bracken fern fronds. Ectatomma tuberculatum has been observed feeding on the nectaries and patrolling the fronds. Ant activity peak was on mid-day during the rainy season. The tropical bracken fern Pteridium esculentum subsp. arachnoideum has a rich (the highest recorded until now on Pteridium species) and diverse ant community on its fronds, mainly on the expanding fronds. The presence of generalist predatory ants (Ectatomma tuberculatum and Solenopsis sp.1) during the entire study period suggests a positive interaction between ants and Pteridium esculentum subsp. arachnoideum.
Resumo: Pteridium é um gênero cosmopolita de samambaias que possui nectários em suas frondes (folhas de samambaias), atraindo formigas. Nectários foliares (ou extraflorais) são glândulas produtoras de néctar que não estão relacionadas com a polinização, mas podem atrair formigas e outros artrópodes. Nectários foliares já foram registrados em 101 espécies de samambaias, pertencentes a 11 gêneros e seis famílias. O objetivo do estudo é caracterizar a comunidade de formigas que visitam as frondes de Pteridium esculentum subsp. arachnoideum, bem como a abundância diária e sazonal das formigas em diferentes estágios foliares. O estudo foi realizado na Mata Atlântica do estado do Rio de Janeiro, Brasil. Foram estabelecidas coletas bimestrais, onde foram marcadas aleatoriamente 30 frondes em expansão e 30 frondes totalmente expandidas. Em cada turno de 1 hora com início às 8h30 e término às 17h30, as frondes marcadas foram observadas quanto à presença de formigas. Trinta e três espécies de formigas foram registradas nas frondes do Pteridium esculentum subsp. arachnoideum, distribuídas em seis subfamílias e 13 gêneros. As espécies mais abundantes foram Solenopsis sp.1 e Ectatomma tuberculatum. Foram registradas oito espécies de formigas forrageando os nectários foliares da samambaia. Ectatomma tuberculatum foi observada se alimentando nos nectários e patrulhando as frondes. As formigas tiveram o pico de atividade ao meio-dia e na estação chuvosa. A samambaia tropical Pteridium esculentum subsp. arachnoideum tem uma elevada riqueza (a maior já registrada até o momento para espécies de Pteridium) e diversidade de formigas em suas frondes, com maior frequência nas frondes não totalmente expandidas. A presença de formigas predadoras generalistas (Ectatomma tuberculatum e Solenopsis sp.1) durante todo o período de estudo sugere uma interação positiva entre as formigas e Pteridium esculentum subsp. arachnoideum.
ABSTRACT
Mining is responsible for drastic ecosystem changes and rehabilitation is used to promote the return of functions after these impacts. In this scenario, we investigated the responses of ant assemblages and diaspore removal by ants to the transformations caused by mining and rehabilitation predicting that (a) the increase in plant density (a proxy for mining intensity) led to an increase in ant richness, percentage of diaspores removed, and changes in species composition that in turn are correlated with changes in environmental variables; (b) the increase in vegetation structure (a proxy for rehabilitation ages) led to an increase in ant richness, percentage of diaspores removed, and changes in species composition that in turn are correlated with changes in environmental variables. Additionally, we also verified which functional groups were primarily responsible for diaspore removal. We sampled arboreal and epigeic ants, diaspore removal by ants, and environmental variables. We found that ant richness and diaspore removal in mining intensity gradient are positively correlated to plant density. Although vegetation structure is positively correlated with ant richness, we found no changes in diaspore removal in rehabilitation gradient. Epigeic omnivore and epigeic generalist predator ants were the most responsible for diaspore removal. Then, we observed that mining decreases ant richness, altering ant assemblages and their functions, and rehabilitation with exotic plants is ineffective to promote the colonization by the main diaspore-removing ants.
Subject(s)
Ants , Ecosystem , Environmental Restoration and Remediation , Mining , Animals , Plants , TreesABSTRACT
Canopy ecology is a fast-growing field, but still a scientific frontier in many ecological aspects. For instance, the hypothesis that tree traits shape patterns in ant-plant interactions lacks data, notably for tropical canopies in different successional stages. In this study, we investigated canopy traits, such as tree height, the presence of extrafloral nectaries (EFNs), connectivity among tree crowns, and successional stage, structure ant-tree interactions in a tropical dry forest (TDF), examining whether these are the determinant factors for ant species richness. We collected ants on trees in early and late successional stages over 2 years, in rainy and dry seasons. In the late successional stage, ant species richness was greater in the taller trees; in the early successional stage, the smallest trees had a greater ant species richness than the taller trees. The EFNs and connectivity among treetops had no effect on ant species richness. We obtained a tree-ant network of the early successional stage, involving 786 interactions among 57 ant species and 75 trees; in the late successional stage, the network had 914 interactions among 60 ant species and 75 trees. There were 27 species of trees in our study, 11 of which (40.7% of all individual trees) had EFNs. The ant-plant interactions were not randomly distributed, suggesting that various biotic factors structured the ant assemblies. This study presents new insights into ant-tree interactions, showing that both tree height and successional stage influence the occurrence of many species of ants in tree canopies of tropical dry forests.
Subject(s)
Ants/physiology , Biodiversity , Forests , Animals , Tropical ClimateABSTRACT
Mutualisms could be evolutionarily unstable, with changes in partner abundances or in the spatial context of interactions potentially promoting their dissolution. We test this prediction using the defense mutualisms between species of the Neotropical genus Cecropia and Azteca ants. A new, multigene phylogeny with representatives of all five genera of Cecropieae (most of them from the Neotropics) and half of the 61 species of Cecropia shows the West African endemic Musanga (2spp.) as sister to Cecropia, implying dispersal from the Neotropics to Africa, with a molecular clock suggesting that this occurred about 23Mya. Cecropia, a genus of neotropical pioneer trees, started diversifying ca. 8Mya. We infer a single origin of specialized symbiosis with Azteca within Cecropia, eight complete losses of this symbiosis, and a potential partner shift involving the replacement of Azteca by Neoponera luteola ants. Niche space modeling based on geo-referenced occurrences of over 9000 collections representing 58 of the 61 species of Cecropia, together with several comparative analyses, implies that mutualism loss is concentrated at high altitudes and on Caribbean islands, with the surprisingly frequent breakdowns potentially facilitated by low species-specificity of interacting Cecropia and Azteca mutualists.
Subject(s)
Ants/physiology , Cecropia Plant/classification , Symbiosis , Tropical Climate , Africa , Altitude , Animals , Phylogeny , Time Factors , West IndiesABSTRACT
Interactions mediated by extrafloral nectary (EFN)-bearing plants that reward ants with a sweet liquid secretion are well documented in temperate and tropical habitats. However, their distribution and abundance in deserts are poorly known. In this study, we test the predictions that biotic interactions between EFN plants and ants are abundant and common also in arid communities and that EFNs are only functional when new vegetative and reproductive structures are developing. In a seasonal desert of northwestern Argentina, we surveyed the richness and phenology of EFN plants and their associated ants and examined the patterns in ant-plant interaction networks. We found that 25 ant species and 11 EFN-bearing plant species were linked together through 96 pairs of associations. Plants bearing EFNs were abundant, representing ca. 19 % of the species encountered in transects and 24 % of the plant cover. Most ant species sampled (ca. 77 %) fed on EF nectar. Interactions showed a marked seasonal pattern: EFN secretion was directly related to plant phenology and correlated with the time of highest ant ground activity. Our results reveal that EFN-mediated interactions are ecologically relevant components of deserts, and that EFN-bearing plants are crucial for the survival of desert ant communities.
ABSTRACT
Animal-plant interactions are important for the recovery of diversity and processes in secondary forests, which increasingly dominate the tropical landscape. We used a combination of observational and experimental approaches to study the interactions of ants with diaspores across a successional gradient of forests in Southern Brazil, from August 2007 to April 2008. In addition to diaspore removal rates, we assessed the species richness, diversity and behaviour of ants interacting with diaspores, in three replicated sites of four successional stages of forests. We recorded 22 ant species interacting with diaspores (an estimated 15% of the total species pool in the region). Species richness and diversity did not differ among successional stages but the behaviour of ants towards diaspores changed with the age of secondary forests. In old successional stages the removal of entire diaspores was more common than in young successional stages of forests. Concordantly, diaspore removal rates were lowest in the youngest successional stage of secondary forests and increased with the age of forests. These results indicate that ant-diaspore interactions in secondary forests are disturbed and lower removal rates in secondary forests are likely to constrain the recruitment of plant populations during secondary succession. Rev. Biol. Trop. 60 (2): 933-942. Epub 2012 June 01.
Las interacciones entre animales y plantas son importantes para la recuperación de la diversidad y los procesos en los bosques secundarios, los cuales cada vez más tienden a dominar el paisaje tropical. Nosotros utilizamos una combinación de métodos experimentales y observaciones para estudiar las interacciones entre hormigas y diásporas a través de un gradiente de sucesión en los bosques del sur de Brasil, entre agosto 2007 y abril 2008. Además de las tasas de eliminación de diásporas, evaluamos la riqueza de especies, la diversidad y el comportamiento de las hormigas que interactúan con las diásporas, con tres repeticiones por sitio de cuatro estadios de sucesión del bosque. Se registraron 22 especies de hormigas que interactúan con diásporas (se estima un 15% del total de especies en la región). La riqueza y diversidad de especies no varió entre las etapas de sucesión, pero el comportamiento de las hormigas hacia las diásporas cambio con la edad de los bosques secundarios. En las etapas sucesionales avanzadas del bosque la eliminación de diásporas fue más común que en las etapas tempranas. En concordancia, las tasas de eliminación de diásporas fueron menores en la etapa más temprana de la sucesión de bosques secundarios y aumenta con la edad de los mismos. Estos resultados indican que las interacciones hormigasdiásporas en los bosques secundarios son alteradas y las menores tasas de extracción en los bosques secundarios es probable que limiten el reclutamiento de las poblaciones de plantas durante la sucesión secundaria.
Subject(s)
Animals , Ants/physiology , Biodiversity , Behavior, Animal/physiology , Trees , Ants/classification , Brazil , Ecosystem , Population DynamicsABSTRACT
Connarus suberosus is a typical species of the Brazilian Cerrado biome, and its inflorescences and young vegetative branches are densely covered by dendritic trichomes. The objective of this study was to report the occurrence of a previously undescribed glandular trichome of this species. The localization, origin and structure of these trichomes were investigated under light, transmission and scanning electron microscopy. Collections were made throughout the year, from five adult specimens of Connarus suberosus near Botucatu, São Paulo, Brazil, including vegetative and reproductive apices, leaves and fruits in different developmental stages, as well as floral buds and flowers at anthesis. Glandular trichomes (GTs) occurred on vegetative and reproductive organs during their juvenile stages. The GTs consisted of a uniseriate, multicellular peduncle, whose cells contain phenolic compounds, as well as a multicellular glandular portion that accumulates lipids. The glandular cell has thin wall, dense cytoplasm (with many mitochondria, plastids and dictyosomes), and a large nucleus with a visible nucleolus. The starch present in the plastids was hydrolyzed during the synthesis phase, reducing the density of the plastid stroma. Some plastids were fused to vacuoles, and some evidence suggested the conversion of plastids into vacuoles. During the final activity stages of the GTs, a darkening of the protoplasm was observed in some of the glandular cells, as a programmed cell death; afterwards, became caducous. The GTs in C. suberosus had a temporal restriction, being limited to the juvenile phase of the organs. Their presence on the exposed surfaces of developing organs and the chemical nature of the reserve products, suggest that these structures are food bodies. Field observations and detailed studies of plant-environment interactions, as well as chemical analysis of the reserve compounds, are still necessary to confirm the role of these GTs as feeding rewards.
Connarus suberosus es una especie típica del bioma Cerrado brasileño, y sus inflorescencias junto con los ramos vegetativos jóvenes están densamente cubiertos por tricomas dendríticas. El objetivo de este estudio es presentar la ocurrencia de un tricoma glandular sin descripción previa para esta especie. La localización, origen y estructura de estos tricomas se observó mediante microscopia óptica, así como electrónica de transmisión y de barrido. Los tricomas glandulares (TGs) se producen en los órganos vegetativos y reproductivos, en sus fases jóvenes. Los TGs consisten en un pedúnculo uniseriado y multicelular, cuyas células contienen compuestos fenólicos, así como un sitio en el cual las células glandulares acumulan compuestos pécticos, almidón y lípidos. La acumulación de aceite en el citosol es impresionante, pues ocupa una gran parte del volumen celular. La porción glandular presenta células con paredes delgadas, un denso citoplasma y un núcleo grande con nucleolo visible. El citoplasma contiene gran cantidad de mitocondrias, plástidos y dictiosomas. El almidón presente en los plástidos se hidroliza durante la fase de síntesis, de tal modo que reduce la densidad del estroma plastidial. Algunos plástidos se fusionan con las vacuolas, además hay pruebas de la conversión de los plástidos en vacuolas. Durante las etapas finales de la actividad de los TGs, se observó un oscurecimiento del protoplasma en algunas de las células glandulares lo que sugiere la existencia de la muerte celular programada; después de lo anterior, los TGs se convierten en caducas. Por lo tanto la aparición de TGs en las superficies expuestas de los órganos en desarrollo en C. suberosus y la naturaleza química de los productos de reserva sugieren que estas estructuras son cuerpos alimenticios. Hay evidencias sobre el papel de estos tricomas en las interacciones planta-hormiga, especialmente en el bioma Cerrado.
Subject(s)
Connaraceae/ultrastructure , Brazil , Connaraceae/chemistry , Connaraceae/classification , Microscopy, ElectronABSTRACT
The aim of this study was to analyze: i) the spider community in vegetative and reproductive branches of Psychotria carthagenensis concerning relative abundance, guild composition and body size distribution; ii) ant abundance in diferent types of branches and iii) the spider behavior when experimentally put in contact with inflorescences covered with ants. There was no difference between vegetative and reproductive branches in relation to spider abundance, composition of guilds and body size distribution of spiders. However, there was a significant difference in ant abundance. In the behavioral experiment, 90 percent of the spiders were expelled from inflorescences by ants; in control treatment, 100 percent remained in the inflorescences. The ant density in different parts of the plant may explain the spider distribution.
Aranhas associadas à Psychotria carthagenensis Jacq. (Rubiaceae). O objetivo deste estudo foi analisar: i) a comunidade de aranhas em ramos vegetativos e reprodutivos de P. carthagenensis quanto à abundancia relativa, composição das guildas e distribuição de tamanhos; ii) a abundância de formigas nos diferentes tipos de ramos; e iii) o comportamento das aranhas quando colocadas em inflorescências cobertas por formigas. Não houve diferença significativa entre ramos vegetativos e reprodutivos em relação à composição de guildas, abundância relativa e distribuição de tamanhos de aranhas. Mas quando comparado à abundância de formigas, houve diferença. No experimento comportamental, 90 por cento das aranhas foram expulsas das inflorescências pelas formigas; no tratamento controle; 100 por cento das aranhas permaneceram nas inflorescências. Para P. carthagenensis, talvez a densidade de formigas em diferentes partes da planta explique melhor a distribuição das aranhas.
Subject(s)
Animals , Ants/physiology , Psychotria/physiology , Spiders/physiology , Host-Parasite Interactions , Population DensityABSTRACT
Formicidae is an abundant group in the soil and is also well distributed in all vegetation strata, representing a good model for studies on vertical stratification of the fauna. The aim of this study was to verify a possible stratification of ant assemblages inhabiting the soil, the lower and the higher vegetation strata. Data was collected in the Serra de Caldas Novas State Park, in an area of cerrado strictu sensu. Ant collection was performed using pitfall traps. A total of 11 traps were placed in the soil, 17 in the lower vegetation stratum (dominated by shrubs and small trees) and 23 in the higher vegetation stratum (dominated by taller, mature trees). Forty-nine species of ants from 15 genera and five subfamilies were collected. Accumulation curves indicated that there is 37.5% more species in the soil than in mature trees and 35% more species in mature trees than in shrubs/young trees. There was not a clear vertical stratification between the soil and the two vegetation strata. Therefore, the species present in the vegetation tended to represent a nested subset of those found in the soil. Even without a clear vertical stratification, the diversity of ants in the cerrado vegetation is high, and part of this diversity appears to be explained by the fact that some species are specialized in nesting and/or foraging in the soil, while others in the vegetation.
Formicidae é um grupo abundante no solo e também largamente distribuído em todos os estratos da vegetação, constituindo-se em um bom modelo biológico para estudos de estratificação vertical. O objetivo geral do trabalho foi determinar os padrões de estratificação da assembléia de formigas em três estratos verticais (solo, estrato arbustivo e estrato arbóreo). Os dados foram coletados no Parque Estadual da Serra de Caldas Novas, em uma área de cerrado strictu sensu. A coleta de formigas foi realizada utilizando-se armadilhas do tipo pitfall. Foram instaladas 11 armadilhas no solo, 17 em plantas do estrato arbustivo e 23 em plantas do estrato arbóreo (uma armadilha por planta). Foi coletado um total de 49 espécies de formigas, pertencentes a 15 gêneros e cinco subfamílias. Através de curvas de acumulação de espécies, pôde-se verificar que existem 37,5% a mais de espécies no solo do que nas árvores e 35% a mais de espécies nas árvores do que nos arbustos. Uma análise de agrupamento indicou uma similaridade mediana entre as espécies de formigas do solo e vegetação (estrato arbustivo e arbóreo). Uma análise de aninhamento demonstrou que as espécies presentes no solo são um subconjunto das espécies presentes nos dois estratos de vegetação. Mesmo sem uma estratificação vertical muito clara, a alta diversidade de formigas encontrada no cerrado pode ser explicada em parte pelo fato de algumas espécies serem especializadas em forragear e/ou nidificar no solo e outras na vegetação.
ABSTRACT
Formicidae is an abundant group in the soil and is also well distributed in all vegetation strata, representing a good model for studies on vertical stratification of the fauna. The aim of this study was to verify a possible stratification of ant assemblages inhabiting the soil, the lower and the higher vegetation strata. Data was collected in the Serra de Caldas Novas State Park, in an area of cerrado strictu sensu. Ant collection was performed using pitfall traps. A total of 11 traps were placed in the soil, 17 in the lower vegetation stratum (dominated by shrubs and small trees) and 23 in the higher vegetation stratum (dominated by taller, mature trees). Forty-nine species of ants from 15 genera and five subfamilies were collected. Accumulation curves indicated that there is 37.5% more species in the soil than in mature trees and 35% more species in mature trees than in shrubs/young trees. There was not a clear vertical stratification between the soil and the two vegetation strata. Therefore, the species present in the vegetation tended to represent a nested subset of those found in the soil. Even without a clear vertical stratification, the diversity of ants in the cerrado vegetation is high, and part of this diversity appears to be explained by the fact that some species are specialized in nesting and/or foraging in the soil, while others in the vegetation.
Formicidae é um grupo abundante no solo e também largamente distribuído em todos os estratos da vegetação, constituindo-se em um bom modelo biológico para estudos de estratificação vertical. O objetivo geral do trabalho foi determinar os padrões de estratificação da assembléia de formigas em três estratos verticais (solo, estrato arbustivo e estrato arbóreo). Os dados foram coletados no Parque Estadual da Serra de Caldas Novas, em uma área de cerrado strictu sensu. A coleta de formigas foi realizada utilizando-se armadilhas do tipo pitfall. Foram instaladas 11 armadilhas no solo, 17 em plantas do estrato arbustivo e 23 em plantas do estrato arbóreo (uma armadilha por planta). Foi coletado um total de 49 espécies de formigas, pertencentes a 15 gêneros e cinco subfamílias. Através de curvas de acumulação de espécies, pôde-se verificar que existem 37,5% a mais de espécies no solo do que nas árvores e 35% a mais de espécies nas árvores do que nos arbustos. Uma análise de agrupamento indicou uma similaridade mediana entre as espécies de formigas do solo e vegetação (estrato arbustivo e arbóreo). Uma análise de aninhamento demonstrou que as espécies presentes no solo são um subconjunto das espécies presentes nos dois estratos de vegetação. Mesmo sem uma estratificação vertical muito clara, a alta diversidade de formigas encontrada no cerrado pode ser explicada em parte pelo fato de algumas espécies serem especializadas em forragear e/ou nidificar no solo e outras na vegetação.
ABSTRACT
The aim of this study was to analyze: i) the spider community in vegetative and reproductive branches of Psychotria carthagenensis concerning relative abundance, guild composition and body size distribution; ii) ant abundance in diferent types of branches and iii) the spider behavior when experimentally put in contact with inflorescences covered with ants. There was no difference between vegetative and reproductive branches in relation to spider abundance, composition of guilds and body size distribution of spiders. However, there was a significant difference in ant abundance. In the behavioral experiment, 90% of the spiders were expelled from inflorescences by ants; in control treatment, 100% remained in the inflorescences. The ant density in different parts of the plant may explain the spider distribution.
Aranhas associadas à Psychotria carthagenensis Jacq. (Rubiaceae). O objetivo deste estudo foi analisar: i) a comunidade de aranhas em ramos vegetativos e reprodutivos de P. carthagenensis quanto à abundancia relativa, composição das guildas e distribuição de tamanhos; ii) a abundância de formigas nos diferentes tipos de ramos; e iii) o comportamento das aranhas quando colocadas em inflorescências cobertas por formigas. Não houve diferença significativa entre ramos vegetativos e reprodutivos em relação à composição de guildas, abundância relativa e distribuição de tamanhos de aranhas. Mas quando comparado à abundância de formigas, houve diferença. No experimento comportamental, 90% das aranhas foram expulsas das inflorescências pelas formigas; no tratamento controle; 100% das aranhas permaneceram nas inflorescências. Para P. carthagenensis, talvez a densidade de formigas em diferentes partes da planta explique melhor a distribuição das aranhas.
ABSTRACT
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.
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.
ABSTRACT
The hypothesis that ants (Pheidole minutula) associated with the myrmecophytic melastome Maieta guianensis defend their host-plant against herbivores was investigated in a site near Manaus, Amazonas, Brazil. M. guianensis is a small shrub that produces leaf pouches as ant domatia. Plants whose ants were experimentally removed suffered a significant increase in leaf damage compared with control plants (ants maintained). Ants patrol the young and mature leaves of Maieta with the same intensity, presumably since leaves of both ages are equally susceptible to herbivore attack. The elimination of the associated ant colony, and consequent increase in herbivory, resulted in reduced plant fitness. Fruit production was 45 times greater in plants with ants than in plants without ants 1 year after ant removal.