Ants Visiting the Post-Floral Secretions of Pericarpial Nectaries in Palicourea rigida (Rubiaceae) Provide Protection Against Leaf Herbivores But Not Against Seed Parasites

Pericarpial nectaries (PNs) have frequently been treated in the literature as extrafloral nectaries (EFNs). This treatment is partly justified by their morphological and functional similarities in attracting bodyguard ants to protect the plant against herbivores. Palicourea rigida is a common Neotropical savanna treelet with tubular yellow flowers that are pollinated by hummingbirds. After pollination, the corolla falls, but the sepal ring remains and keeps the nectaries active over the ovarium throughout fruit development stages. Using a standard ant-exclusion experiment, we tested whether these PNs attract ants to protect the developing fruits against seed parasites and the leaves against chewing herbivores. We analyzed the differences between the initial and final leaf area. Before full fruits maturity, they were collected and taken to the laboratory for weighing and to observe wasp emergence. The number of wasps per fruit and per plant was recorded. The results showed that after pollination, the floral nectaries of P. rigida act as EFNs, attracting visiting ants. Ant-tended plants lost significantly less leaf area and had heavier fruits than untended plants. However, the ants did not protect the fruits against seed-parasitic wasps. In P. rigida, the post-floral secretions of PNs play the same role as EFNs, and the ant-plant mutualism is context-dependent based on the type of herbivore and the plant tissue consumed

Ants Visit Nectaries Of Epidendrum Denticulatum (orchidaceae) In A Brazilian Rainforest: Effects On Herbivory And Pollination.

Epidendrum denticulatum (Orchidaceae) produces nectar on the petioles of buds, flowers, and fruits (extrafloral nectaries) but no nectar is found on its flowers, and it is probably a deceptive species. In the Brazilian Atlantic rainforest, some aspects of both the ecology and behavior of Camponotus sericeiventris (Formicinae) and Ectatomma tuberculatum (Ponerinae), two ant species foraging on E. denticulatum extrafloral nectaries, were investigated. Both experiments, using termites as baits and field observations, suggest that these ant species are able to prevent reproductive organ herbivory, without affecting pollinator behaviour. Since a low fruit set is often cited as a characteristic of the family, especially for deceptive species, ants attracted to orchid inflorescences protect reproductive structures and increase the probability of pollination success. Epidendrum denticulatum flowers were visited and probably pollinated by Heliconius erato (Nymphalidae) and Euphyes leptosema (Hesperiidae).63455155

EFECTO DE UNA FUENTE DE ALIMENTO EXPERIMENTAL SOBRE UNA ASOCIACIÓN HORMIGA-HEMIPTERO

In order to assess if ants attracted to honeydew-producing Hemiptera switched food sources when offered an additional, considerably rich and abundant food source, we studied the interaction between the plant Solanum lycocarpum (Solanaceae), an efn-lacking shrub, the predominantly diurnal ant Camponotus crassus (Hymenoptera: Formicidae), and two species of membracids (Enchenopa spp.; Homoptera: Membracidae). The study was done during September of 1999 at the Reserva Ecológica of IBGE (ca. 35 km S of Brasilia-DF, Brasil). The results show that ants were attracted both to the experimental food source and to the membracids. Moreover, the mean number of ants visiting the experimental nectary was significantly higher than those visiting the membracids. However, the membracids were never left unattended, which suggests that ants, even though presented with an abundant and rich food source, do not abandon other sources. The latter can be explained due to an increment in the honeydew production rate by the membracids, thus the attention levels of ants does not vary Another possibility is the fidelity of worker ants to a food source and its location. To show that ants switch food sources based on quality and/or quantity, and not merely based of their presence and/or absence, requires future research, both for plants with and without extrafloral nectaries.Estudiamos la asociación entre el arbusto sin nectarios extraflorales (NEF) Solanum lycocarpum (Solanaceae), la hormiga Camponotus crassus (Hymenoptera: Formicidae) y dos especies de membrácidos (Enchenopa spp., Hemiptera: Membracidae) productores de ambrosía, para determinar si las hormigas abandonarían a los membrácidos al ofrecerles experimentalmente una fuente de alimento considerablemente rica y abundante. El estudio se realizó en septiembre de 1999 en la Reserva Ecológica del Instituto Brasileiro de Geografía y Estadística (IBGE) (ca. 35 km al sur de Brasilia-DF, Brasil). Los resultados muestran que las hormigas fueron atraídas tanto al nectario experimental como a los membrácidos. Más aún, el número promedio de hormigas visitando a los nectarios experimentales fue significativamente mayor que el de las que visitaron a los membrácidos. Sin embargo, los membrácidos nunca fueron abandonados, lo que sugiere que las hormigas, a pesar de explotar una fuente abundante de alimento, no abandonan otras fuentes. Lo anterior puede explicarse por un incremento en la tasa de producción de ambrosía por los membrácidos, por lo que los niveles de atención de las hormigas hacia ellos no varía aún en la presencia de una fuente alternativa de alimento. Otra posibilidad puede ser la lealtad de las obreras por un recurso y su ubicación; algunos individuos retornan siempre a un sitio con una fuente de alimento. El poder demostrar que las hormigas cambian de recurso alimenticio basadas en cantidad y/o calidad, y no solamente basadas en la presencia o ausencia de los mismos, requiere de investigaciones futuras, tanto para plantas con como sin NEF

Understanding the Complex Structure of a Plant-Floral Visitor Network from Different Perspectives in Coastal Veracruz, Mexico

Our premise was to understand the basic structure of the flower-flower visitor community at La Mancha in Veracruz, Mexico. We used network analyses to study the structure of this community. In particular, to analyze, (1) if flower color and shape (“as a limited portion of the traditional floral syndromes definition”) were linked to the arrival of certain floral visitors, (2) if visits to flowers were generalist, specific and/or modular; and (3) which plant species, if any, in the core of the network could affect the stability of floral visitors. In order to analyze the organization of the plant-floral visitor community, we prepared network graphics using Pajek, nestedness (as NODF) with Aninhado, and modularity with the SA algorithm. The network obtained was nested suggesting that generalist species (with the most associations) were interacting with specialists (with fewer associations). Furthermore, floral visitors (Hymenoptera, Diptera, Lepidoptera and Trochiilidae) did not exhibit a particular preference for a specific flower color or shape, each pollinator group visited most flowers/colors/shapes considered. The same was similar for all 14 resulting modules. As in other studies, we suggest that pollination leans to generalization rather than to specialization. We suggest that maybe seasonality/food resource could be the factors to analyze as the next step in floral visits which may be the answer to modularity in this seasonal ecosystem

Topological structure of plant-bee networks in four Mexican environments

We analyzed the topological structure (e.g., links per species, connectance, core-periphery analyses, specialization, nestedness, modularity) of plant-bee interactions of four areas in Mexico. We used qualitative data (binary networks). Mexico exhibits a complex geography and community variation that can affect bee networks. Network architecture is variable within large spatial scales, thus our results should vary according to site characteristics (La Mancha and Totula in Veracruz, Carrillo Puerto in Quintana Roo, and the Tehuacan-Cuicatlan valley, in Puebla), type of vegetation, endemism, altitude, size of area sampled. Network topology varied among sites, and the presence of nested or modular patterns was analyzed for robustness to simulated species extinctions. The lowest species richness was recorded for the Quintana Roo site (15 plant, 25 bee species), and the highest for the Tehuacan-Cuicatlan valley site (88 plant, 231 bee species). There was a tendency to have more connected networks when species richness was low and networks with greater species richness had a higher number of interactions. The distribution of interactions differed between environments but not due to network size and all were significantly nested. The robustness to cumulative extinctions showed a different pattern at each site; the most robust network was at Carrillo Puerto, which also was the site with less species. Sites with more endemic species (e.g. Tehuacan) had more specialized interactions, and were more susceptible to extinction

Interações entre formigas e plantas com nectários extraflorais na vegetação do cerrado

Extrafloral nectaries (EFNs) are nectar-secreting glands not directly involved with pollination which may occur on virtually all above-ground plant parts of angiosperms. Recent studies revealed that such glands are widely distributed amongst the woody flora of the Brazilian cerrados. Plants bearing EFNs are visited day and night by a diverse assemblage of nectarivorous ants. In this review we present the data gathered during the past 15 years on the interaction between ants and EFN-bearing plants in cerrado vegetation. Field experiments indicate that ants visiting EFNs may prey or attack insect herbivores on the plant foliage, significantly reducing herbivore damage to leaves, buds or flowers. As a response, some herbivore species have developed an array of mechanisms to circumvent the ants' deterring capacities on their host plants. Ant-derived benefits to plants, however, may vary with the species of visiting ant, with the defensive tactics of the associated herbivores, as well as with the plant species. We discuss the results obtained for different cerrado plant species, and suggest some promising topics for future experimental investigation.Nectários extraflorais (NEFs) são glândulas de néctar não relacionadas com o processo de polinização da planta e que podem ocorrer virtualmente em todas as estruturas vegetativas e reprodutivas de angiospermas. Estudos recentes revelaram que NEFs ocorrem em diversas espécies de arbustos e árvores dos cerrados brasileiros. Plantas portadores destas glândulas são visitadas de dia e de noite por diversas espécies de formigas nectarívoras do cerrado. Nesta revisão apresentamos os dados obtidos nos últimos 15 anos sobre a interação entre formigas e plantas com NEFs em vegetação de cerrado. Estudos experimentais no campo indicam que as formigas visitantes de NEFs podem predar ou injuriar insetos herbívoros que encontram sobre as plantas, reduzindo significativamente as taxas de herbivoria sobre as folhas, botões ou flores. Em resposta, algumas espécies de herbívoros desenvolveram vários mecanismos para evitar o ataque das formigas sobre suas plantas hospedeiras. Os benefícios oferecidos às plantas pelas formigas visitantes, entretanto, podem variar com a agressividade da espécie de formiga, com as estratégias defensivas apresentadas pelos insetos herbívoros, bem como com a espécie de planta. Os resultados obtidos para diferentes espécies de plantas de cerrado são discutidos, indicando áreas promissoras para estudos experimentais futuros.161176Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Ants and Guayaquila xiphias (Hemiptera: Membracidae) on Schefflera vinosa (Araliaceae) : the role of cuticular lipids in the chemical camouflage of treehoppers

Orientadores: Paulo Sergio Moreira Carvalho de Oliveira, Jose Roberto TrigoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de BiologiaMestradoMestre em Ecologi

Caracterización morfológica de los nectarios extraflorales en especies vegetales de la Amazonia brasileña

Background and Aims: Extrafloral nectaries (EFNs) are secretory glands of an aqueous solution composed mainly of sugars, amino acids and lipids, frequently used as food resource by ants, which tend to protect their host plants against herbivorous insects. Although the Amazon forest is recognized worldwide for its high plant diversity, few studies have been carried out in the region that characterize the different morphotypes of EFNs. In this context, our main aim was to perform a brief morphological description of EFNs in the Brazilian Amazonian rainforest. Methods: We established a plot of 6250 m2 in ten forest fragments situated in the state of Acre, Brazilian Amazon. In these plots, we performed intensive field surveys to locate EFN-bearing plant species. Subsequently, we used scanning electron microscopy images to morphologically characterize the EFNs. The morphological descriptions included information about the life form of EFN-bearing plant species, morphotypes of EFNs and their location in different plant structures. Key results: We morphologically characterized 67 EFN-bearing plant species, distributed in 28 genera and 19 families. The botanical families with the highest taxonomic representativeness were Fabaceae, Bignoniaceae and Malpighiaceae. Lianas were the life form with the largest number of EFN-bearing plant species, while elevated EFNs were the most frequent morphotype. Conclusions: The high frequency of elevated EFNs evidences the importance of the ant defense system against herbivory in these Brazilian Amazonian forests, since it has been documented in others works that this morphotype secretes a larger nectar volume, which is an advantage in relation to the attraction potential. Finally, our results indicate the existence of a high diversity of EFN-bearing plant species in this region of the Brazilian Amazon, and an important morphological diversity of associated extrafloral nectaries.Antecedentes y Objetivos: Los nectarios extraflorales (NEFs) son glándulas secretoras de una solución acuosa compuesta principalmente de azúcares, aminoácidos y lípidos, frecuentemente utilizada como recurso alimenticio por hormigas, que tienden a proteger sus plantas hospederas contra insectos herbívoros. Aunque la selva amazónica es reconocida mundialmente por su alta diversidad de plantas, pocos estudios se han realizado en la región que caracterizan las diferentes formas de NEFs. En este contexto, nuestro principal objetivo fue realizar una descripción morfológica de los NEFs en una selva amazónica brasileña. Métodos: Establecimos una parcela de 6250 m2 en diez fragmentos de bosque situados en el estado de Acre, Amazonía Brasileña. En estas parcelas, realizamos recorridos de campo intensivos para localizar especies de plantas portadoras de NEFs. Posteriormente, utilizamos imágenes de microscopía electrónica de barrido para caracterizar morfológicamente los NEFs. Las descripciones morfológicas incluyeron información sobre la forma de vida de las especies de plantas portadoras de NEFs, morfotipos de NEFs y su ubicación en las diferentes estructuras de la planta. Resultados clave: Caracterizamos morfológicamente 67 especies de plantas portadoras de NEFs, distribuidas en 28 géneros y 19 familias. Las familias botánicas con mayor representatividad taxonómica fueron Fabaceae, Bignoniaceae y Malpighiaceae. Las lianas fueron la forma de vida que presentó más especies de plantas portadoras de NEFs, mientras que los NEFs de tipo elevado fueron los más frecuentes. Conclusiones: La mayor frecuencia de NEFs de tipo elevado evidencia la importancia del sistema de defensa de hormigas contra la herbivoria en esta selva amazónica brasileña, ya que se ha documentado en otros trabajos que este morfotipo secreta un mayor volumen de néctar, lo que es una ventaja en relación con el potencial de atracción. Finalmente, nuestros hallazgos indican la existencia de una alta diversidad de especies de plantas portadoras de NEFs en esta región de Amazonía Brasileña, y una importante diversidad morfológica de nectarios extraflorales asociados

Impacts of major predators on tropical agroforest arthropods: comparisons within and across taxa

In food web studies, taxonomically unrelated predators are often grouped into trophic levels regardless of their relative importance on prey assemblages, multiple predator effects, or interactions such as omnivory. Ants and birds are important predators likely to differentially shape arthropod assemblages, but no studies have compared their effects on a shared prey base. In two separate studies, we excluded birds and ants from branches of a canopy tree ( Inga micheliana ) in a coffee farm in Mexico for 2 months in the dry and wet seasons of 2002. We investigated changes in arthropod densities with and without predation pressure from (1) birds and (2) ant assemblages dominated by one of two ant species ( Azteca instabilis and Camponotus senex ). We first analyzed individual effects of each predator (birds, Azteca instabilis , and C. senex ) then used a per day effect metric to compare differences in effects across (birds vs ants) and within predator taxa (the two ant species). Individually, birds reduced densities of total and large arthropods and some arthropod orders (e. g., spiders, beetles, roaches) in both seasons. Azteca instabilis did not significantly affect arthropods (total, small, large or specific orders). Camponotus senex , however, tended to remove arthropods (total, small), especially in the dry season, and affected arthropod densities of some orders both positively and negatively. Predators greatly differed in their effects on Inga arthropods (for all, small, large, and individual orders of arthropods) both in sign (±) and magnitudes of effects. Birds had stronger negative effects on arthropods than ants and the two dominant ant species had stronger effects on arthropods in different seasons. Our results show that aggregating taxonomically related and unrelated predators into trophic levels without prior experimental data quantifying the sign and strengths of effects may lead to a misrepresentation of food web interactions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47705/1/442_2004_Article_1561.pd