Host diversity and environmental variables as determinants of the species richness of the parasitoids of leaf-cutting ants

Aim Because of the obligatory relationship between endoparasitoids and their hosts, we presume that hosts exert strong selection pressure on parasitoids. One prediction is a positive relationship between host diversity and parasitoid richness. This relationship could be the product of resource availability which could lead to more opportunities for speciation, or could represent shared responses to the environment by both groups.Location Argentina and Paraguay.Methods We sampled a 1800-km transect to test for a correlation between the richness of leaf-cutting ant hosts and their phorid parasitoids. Regression models were used to assess if host and environmental variables could explain phorid species richness at nest, hectare and locality spatial scales. We used canonical correspondence analysis (CCA) to explore if there were similar responses of phorid species to particular host and environmental variables at different spatial scales, and partial CCA to separate the relative importance of both groups of variables.Results Phorid richness was positively correlated with host richness. Host richness/abundance accounted for 20-53% of the variation in parasitoid richness at the hectare and locality scales of analysis, with most of the variation accounted for by ant abundance. We were not able to assess the prediction at the nest scale as only one phorid species was found at most nests. Climatic variables did not explain phorid species richness once host variables were in the models. Partial CCA showed that host-related variables accounted for most of the variance associated with phorid species ordination at the nest and hectare scales, but not at the largest grain, the locality, where climatic variables were more important. However, most phorid species did not show particular positions along the climatic gradient.Main conclusions The association between parasitoid richness and host richness and abundance, and the overall weak associations with environmental variables, suggest that these host variables are key factors influencing parasitoid speciation.Fil: Elizalde, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Folgarait, Patricia Julia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; Argentin

Por qué tienen importancia en la actualidad los inicios de Chris Burden

Los acontecimientos de la historia mundial reciente, sobre todo el conflicto militar en Irak, nos traen a la mente cuestiones de importancia histórica, social y política que se sugirieron en la obra de Chris Burden, artista de performance de California, especialmente en la primera mitad de la década de los setenta. Una referencia tan clara a cuestiones actuales en la obra de arte plantea preguntas acerca del estado de estas obras como arte, frente a la documentación o editorialización, en el sentido normal de esa categoría de la especie humana. ¿Desarrolla el arte, en este caso, una actividad de transgresión que la expulsa de los discursos normales del mundo del arte

Behavioral discrimination between monogyne and polygyne red fire ants (Hymenoptera: Formicidae) in their native range

Nestmate recognition among social insects is presumed to restrict non-nestmates from exploiting nest resources. Here, we developed aggression bioassays to assess the discrimination behaviors of both polygynous and monogynous forms of the red fire ant, Solenopsis invicta Buren, during symmetrical interactions in neutral arenas. Workers from polygyne colonies exhibited risk avoidance behaviors; that is, defensive postures or the avoidance of direct contact during interactions. Workers from monogyne colonies always exhibited aggressive behaviors in the form of physical or chemical attacks. In interactions between both, monogyne workers usually started the aggression by surrounding and biting the polygyne ants. Polygyne S. invicta workers also distinguished nestmates from foreigners, but their response was not as aggressive as that of monogynes. The proposed ethogram that we constructed identified monogyne and polygyne forms of S. invicta colonies in concordance with current measures, including number of queens, and expression of the Gp-9 gene.Fil: Chirino, Monica Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Centro de Estudios e Investigación; ArgentinaFil: Gilbert, Lawrence E.. University of Texas at Austin; Estados UnidosFil: Folgarait, Patricia Julia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Centro de Estudios e Investigación; Argentin

Growth and conidiation response of escovopsis weberi (Ascomycota: Hypocreales) against the fungal cultivar of acromyrmex lundii (Hymenoptera: Formicidae)

Leaf-cutter ants (Acromyrmex and Atta spp.) exhibit ancient and complex interactionswith the symbiotic fungus Leucoagaricus (Basidiomycetes: Agaricales) from which they feed, and withthe virulent and speciÞc fungus Escovopsis weberi J.J. Muchovej & Della Lucia (Ascomycetes:Hypocreales) that attacks the antsÕ fungal gardens. This system offers a unique opportunity to studypossible avenues for replacing polluting pesticides with a biological control agent against the ants. Weisolated both Leucoagaricus sp. and E. weberi from the gardens of Acromyrmex lundii Gue´ rin-Me´ nevillecolonies and confronted them with each other by growing Leucoagaricus on petri dishes and placinginoculated pieces of agar inoculated with E. weberi at the edges. Here we present growth curves ofLeucoagaricus sp. and E. weberi in the absence of each other, as a baseline to which we compare theeffect of the fungi on each other. As expected, we found a negative effect of E. weberi on the ant cultivarfrom different colonies of A. lundii. E. weberi increased its growth rate, as well as the levels ofconidiation, in the presence of the ant cultivar. We determined that a soluble and diffusible compound,released by the cultivar, triggered, was responsible for, or did both for the increased levels ofconidiation in E. weberi, and that this response was reversible. We discuss why our results areencouraging from a biological control perspective.Fil: Folgarait, Patricia Julia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Hormigas; ArgentinaFil: Marfetan, Jorge Ariel. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Hormigas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cafaro, M. J.. Universidad de Puerto Rico; Puerto Ric

Preliminary in vitro insights into the use of natural fungal pathogens of leaf-cutting ants as biocontrol agents

Leaf-cutting ants are one of the main herbivores of the Neotropics, where they represent an important agricultural pest. These ants are particularly difficult to control because of the complex network of microbial symbionts. Leaf-cutting ants have traditionally been controlled through pesticide application, but there is a need for alternative, more environmentally friendly, control methods such as biological control. Potential promising biocontrol candidates include the microfungi Escovopsis spp. (anamorphic Hypocreales), which are specialized pathogens of the fungi the ants cultivate for food. These pathogens are suppressed through ant behaviors and ant-associated antibiotic-producing Actinobacteria. In order to be an effective biocontrol agent, Escovopsis has to overcome these defenses. Here, we evaluate, using microbial in vitro assays, whether defenses in the ant-cultivated fungus strain (Leucoagaricus sp.) and Actinobacteria from the ant pest Acromyrmex lundii have the potential to limit the use of Escovopsis in biocontrol. We also explore, for the first time, possible synergistic biocontrol between Escovopsis and the entomopathogenic fungus Lecanicillium lecanii. All strains of Escovopsis proved to overgrow A. lundii cultivar in less than 7 days, with the Escovopsis strain isolated from a different leaf-cutting ant species being the most efficient. Escovopsis challenged with a Streptomyces strain isolated from A. lundii did not exhibit significant growth inhibition. Both results are encouraging for the use of Escovopsis as a biocontrol agent. Although we found that L. lecanii can suppress the growth of the cultivar, it also had a negative impact on Escovopsis, making the success of simultaneous use of these two fungi for biocontrol of A. lundii questionable.Fil: Folgarait, Patricia Julia. Universidad Nacional de Quilmes; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gorosito, Norma Beatriz. Universidad Nacional de Quilmes; ArgentinaFil: Poulsen, Michael. University of Wisconsin; Estados UnidosFil: Currie, Cameron R.. University of Wisconsin; Estados Unido

A small parasitoid of fire ants, pseudacteon obtusitus (Diptera: Phoridae): native range ecology and laboratory rearing

The high diversity within a guild of Pseudacteon Coquillet (Diptera: Phoridae) parasitoid flies hosted by the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae), may be based on several niche axes, including host size specialization, host location cues, climatic responses, and tolerances. The recently described species, Pseudacteon obtusitus Plowes, Folgarait, and Gilbert (Diptera: Phoridae), is one of the smallest species in this group (with a thorax width of only 0.3 mm), and appears to locate ant hosts on foraging trails as well as at nest disturbances. Here we examine the ecology, phenology, and development of this parasitoid at sites in Corrientes, Argentina. Pseudacteon obtusitus has 2 seasons of peak abundance, and exhibits low tolerance for cold temperatures or extended cold periods. It preys on the smallest ant workers (typically 0.6 mm head width) independent of the ant size offered, and has a male biased sex ratio (mean 2.78:1). Developmental times ranged from 35 d at 27 °C to 44 d at 22 °C. This species holds interest for inclusion among the multi-species assemblage of parasitoid flies considered for biological control of S. invicta in its invasive range in North America.La gran diversidad dentro del gremio de moscas parasitoides del género Pseudacteon Coquillet (Diptera: Phoridae), específicas de las hormigas de fuego, Solenopsis invicta Buren (Hymenoptera: Formicidae), puede estar basada en varios ejes de nicho incluyendo una especialización por el tamaño del huésped, claves de localización del huésped y respuestas climáticas o tolerancias. La especie recientemente descripta, Pseudacteon obtusitus Plowes, Folgarait, Gilbert (Diptera: Phoridae), es una de las más pequeñas de este grupo con un ancho de tórax de 0.3 mm y parece localizar a las hormigas huésped en los caminos de forrajeo así como en nidos disturbados. En este trabajo se examina la ecología, fenología y desarrollo de esta especie en sitios de Corrientes, Argentina. Pseudacteon obtusitus tiene 2 picos de abundancia y posee poca tolerancia a las temperaturas bajas o períodos largos de frío. Esta especie ataca a las obreras más pequeñas (típicamente de 0.6 mm de ancho de cabeza) independientemente del tamaño de huésped ofrecido, y tiene una relación de sexos sesgada hacia los machos (promedio 2.78:1). Los tiempos de desarrollo varían de 35 días a 27 °C hasta 44 días a 28 °C. Esta especie es interesante para incluirla en el ensamble multi-específico de moscas parasitoides consideradas para el control biológico de Solenopsis invicta en su rango de invasión en América del Norte.Fil: Folgarait, Patricia Julia. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Hormigas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Plowes, Robert M.. University of Texas; Estados UnidosFil: Gomila Molina, Carolina Florencia. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología. Laboratorio de Hormigas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; ArgentinaFil: Gilbert, Lawrence E.. University of Texas; Estados Unido

development and calibration of a cfd based model of the bed fusion slm additive manufacturing process aimed at optimising laser parameters

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Ground state of N=Z doubly closed shell nuclei in CBF theory

The ground state properties of N=Z doubly closed shell nuclei are studied within correlated basis function theory. A truncated version of the Urbana v14 realistic potential, with spin, isospin and tensor components, is adopted, together with state dependent correlations. Fermi hypernetted chain integral equation and single operator chain approximation are used to evaluate density, distribution function and ground state energy of 16O and 40Ca. The results favourably compare with the available, variational MonteCarlo estimates and provide a first substantial check of the accuracy of the cluster summation method for state dependent correlations. We achieve in finite nuclei at least the same level of accuracy in the treatment of non central interactions and correlations as in nuclear matter. This opens the way for a microscopic study of medium heavy nuclei ground state using present days realistic hamiltonians.Comment: 35 pages (LateX) + 3 figures. Phys.Rev.C, in pres