Land use drives detritivore size structure and decomposition through shifts in resource quality and quantity

Land use change and nutrient pollution are two pervasive stressors that can modify carbon cycling, as they influence the inputs and the transformation of detritus. Understanding their impact on stream food webs and on diversity is particularly pressing, as streams are largely fuelled by detrital material received from the adjacent riparian environment. Here we assess how a switch from native deciduous forest to Eucalyptus plantations and nutrient enrichment alter the size distribution of stream detritivore communities and decomposition rates of detritus. As expected, more detritus resulted in higher size-independent, or overall, abundance (i.e. higher intercept of size spectra). This change in overall abundance was mainly driven by a change of the relative contribution of large taxa (Amphipoda and Trichoptera), which changed from an average relative abundance of 55.5 to 77.2 % between the sites compared for resource quantity differences in our study. In contrast, detritus quality modified the relative abundance of large vs small individuals (i.e. size spectra slopes), with shallow slopes of size spectra (proportionately more large individuals) associated with sites with nutrient-richer waters and steeper slopes (proportionately fewer large individuals) associated with sites draining Eucalyptus plantations. Decomposition rates of alder leaves due to macroinvertebrates increased from 0.0003 to 0.0142 when relative contribution of large organisms increased (modelled slopes of size spectra: −1.00 and − 0.33, respectively), highlighting the importance of large sized individuals for ecosystem functioning. Our study reveals that land use change and nutrient pollution can greatly impair the transfer of energy through the detrital or ‘brown’ food web by means of intra- and inter-specific responses to quality and quantity of the detritus. These responses enable linking land use change and nutrient pollution to ecosystem productivity and carbon cycling.This work was carried out with financial support from the EU Commission within the RivFunction project (contract EVK1-CT-2001-00088). AL acknowledges the financial support by the mobility program Ikermugikortasuna-2019 of the Basque Government

Water diversion and pollution interactively shape freshwater food webs through bottom-up mechanisms

[EN] Water diversion and pollution are two pervasive stressors in river ecosystems that often co-occur. Individual effects of both stressors on basal resources available to stream communities have been described, with diversion reducing detritus standing stocks and pollution increasing biomass of primary producers. However, interactive effects of both stressors on the structure and trophic basis of food webs remain unknown. We hypothesized that the interaction between both stressors increases the contribution of the green pathway in stream food webs. Given the key role of the high-quality, but less abundant, primary producers, we also hypothesized an increase in food web complexity with larger trophic diversity in the presence of water diversion and pollution. To test these hypotheses, we selected four rivers in a range of pollution subject to similar water diversion schemes, and we compared food webs upstream and downstream of the diversion. We characterized food webs by means of stable isotope analysis. Both stressors directly changed the availability of basal resources, with water diversion affecting the brown food web by decreasing detritus stocks, and pollution enhancing the green food web by promoting biofilm production. The propagation of the effects at the base of the food web to higher trophic levels differed between stressors. Water diversion had little effect on the structure of food webs, but pollution increased food chain length and trophic diversity, and reduced trophic redundancy. The effects at higher trophic levels were exacerbated when combining both stressors, as the relative contribution of biofilm to the stock of basal resources increased even further. Overall, we conclude that moderate pollution increases food web complexity and that the interaction with water abstraction seems to amplify this effect. Our study shows the importance of assessing the interaction between stressors to create predictive tools for a proper management of ecosystems.Ministerio de Economia, Industria y Competitividad, Gobierno de Espana, Grant/Award Number: GL2016-77487-R; European Social Fund; Diputacion Foral de Bizkaia; Serra Hunter Fellow; Labex, Grant/Award Number: ANR-10-LABX-41; H2020 European Research Council; Eusko Jaurlaritza; Consejo Nacional de Investigaciones Cientificas y Tecnicas; FRAGCLIM Consolidator, Grant/Award Number: 72617

La arquitectura de la naturaleza: complejidad y fragilidad en redes ecológicas

Algo que caracteriza a los ecosistemas en el presente es su acelerada pérdida de biodiversidad. Dentro de cien mil años un paleontólogo clasificaría nuestra época de la historia de la Tierra en el grupo de las extinciones en masa. Algunos efectos directos de esta pérdida de biodiversidad, por ejemplo, la reducción de la productividad primaria, son relativamente conocidos. Otros, de carácter más indirecto pero no por ello menos relevantes, aún son prácticamente desconocidos. Nos referimos a la compleja red de interaciones ecológicas. En este artículo se apuntan algunos efectos directos e indirectos recientemente descubiertos a partir del análisis de interacciones tróficas. Estas redes ecológicas son muy frágiles ante perturbaciones que eliminan las especies más conectadas, resultando en un gran número de coextinciones de otras especies del ecosistema. Se discuten las implicaciones que estas observaciones pueden tener para (1) entender la organización de los ecosistemas y su respuesta a perturbaciones, (2) la relevancia y definición de especies-clave, (3) mejorar las estimas de las actuales tasas de extinción, y (4) definir objetivos dentro de la Biología de la Conservación

Food-web energy fluxes, energy transfer efficiency, and diversity respond distinctively to pollution and water diversion in rivers

Water diversion and pollution are two pervasive stressors for river ecosystems that often co-occur. The individual effects of both stressors on river communities and energy transfer across the food webs are well described; however, how they interact remains unknown. We hypothesised that low-to-moderate nutrient pollution gradient would cause a mild increase in invertebrate driven herbivory and water diversion a strong reduction in detritivory, whereas their joint effect would reduce invertebrate abundance and diversity, as well as total energy fluxes (from basal resources to invertebrates and fish). We also expected a shift in body size spectra slope with increased energy transfer between trophic levels with moderate pollution, but not with water diversion. To test these hypotheses, we selected four rivers across a range of nutrient pollution levels (a proxy of water quality) subject to similar water diversion schemes and compared food webs upstream and downstream of their diversion weirs. Both stressors changed the availability of basal food resources. Nutrient pollution induced changes in the green food web (i.e., biofilm-based) by enhancing biofilm stocks, whereas water diversion affected the brown food web (i.e., detritus-based) by decreasing stocks of detritus. The propagation of the effects to higher trophic levels differed with each stressor: pollution increased the homogeneity of community within the reach, whereas water diversion made communities more heterogeneous. Moreover, pollution induced changes within omnivores, increasing herbivory and carnivory, whereas diversion reduced the total energy fluxes through a decrease in detritivory, especially with pollution. Although most of the variables studied seemed to be more sensitive to water diversion, pollution often accentuated the response, being the interaction between both stressors more explanatory than any of the two stressors on its own. The effects of water diversion on diversity and energy flow through food webs are more detrimental to moderately polluted rivers than to systems with high quality water. We show that the use of tools merging knowledge on trophic relationships among species and their metabolic requirements enables disturbances to be detected that would otherwise go unnoticed.Spanish Department of Economy, Industry and Competitiveness. Grant Number: GL2016-77487-R European Social Fund Plus Basque Government. Grant Number: Consolidated Research Group IT951-16 Biscay Province Council. Grant Number: 61/2015 European Research Council. Grant Number: FRAGCLIM Consolidator Grant(726176) Laboratoires d'Excellences (LABEX)' TULIP. Grant Number: ANR-10-LABX-4

6 Cuentos 6

Recoge los seis cuentos premiados en el primer certamen de cuentos organizado por el Colegio Público José Gutiérrez Solana de Madrid, correspondiente al curso académico 1984-1985. El certamen otorgó primer y segundo premio, más un accesit en cada una de las dos categorías. Los cuentos premiados en la categoría primera etapa son 'En busca de la felicidad', 'La margarita que se quedó sin pétalos' y 'La carrera del globo'; y en la categoría segunda etapa son '7432 las últimas horas', 'El más voraz' y 'Cuervo blanco'..MadridES

Treated and highly diluted, but wastewater still impacts diversity and energy fluxes of freshwater food webs

Wastewater treatment plants (WWTPs) have greatly improved water quality globally. However, treated effluents still contain a complex cocktail of pollutants whose environmental effects might go unnoticed, masked by additional stressors in the receiving waters or by spatiotemporal variability. We conducted a BACI (Before-After/Control-Impact) ecosystem manipulation experiment, where we diverted part of the effluent of a large tertiary WWTP into a small, unpolluted stream to assess the effects of a well-treated and highly diluted effluent on riverine diversity and food web dynamics. We sampled basal food resources, benthic invertebrates and fish to search for changes on the structure and energy transfer of the food web with the effluent. Although effluent toxicity was low, it reduced diversity, increased primary production and herbivory, and reduced energy fluxes associated to terrestrial inputs. Altogether, the effluent decreased total energy fluxes in stream food webs, showing that treated wastewater can lead to important ecosystem-level changes, affecting the structure and functioning of stream communities even at high dilution rates. The present study shows that current procedures to treat wastewater can still affect freshwater ecosystems and highlights the need for further efforts to treat polluted waters to conserve aquatic food webs.This research was supported by the EU Seventh Framework Programme (GLOBAQUA; 603629-ENV-2013-6.2.1). Authors also acknowledge the financial support from the Basque Government (Consolidated Research Group IT951-16) and the pre-doctoral fellowship from the Basque Government (I. de Guzman). D. von Schiller is a Serra Húnter Fellow. J. M. Montoya is funded by the FRAGCLIM Consolidator Grant (number 726176) from the European Research Council under the EU Horizon 2020 Research and Innovation Program and by the “Laboratoires d’Excellences (LABEX)" TULIP (ANR-10-LABX-41). Authors are especially grateful to Libe Solagaistua, Olatz Pereda, Vicki Perez, Miren Atristain, Janire Diez, Madalen Goitia, Laura Sierra and Kelly Huamantumba for their assistance during field campaigns and laboratory analyses, and to the staff of the Apraitz WWTP for continuous support during the experiment. Mario Brauns and Ines Locker are also gratefully acknowledged for providing data on resource quality

Educación religiosa en América Latina y el Caribe : reflexiones y voces plurales para caminos pedagógicos interculturales

Compilador: José Mario Méndez Méndez Sección 1. Diversidad de Convicciones: creencias y espiritualidades. Sección 2. Textualidades Sagradas Sección 3. Ciencias de la religión. Sección 4. Expresiones de la diversidad. Sección 5. Religión y Cultura. Sección 6. Aportes pedagógicos. Sección 7. Educación religiosa en América Latina. Sección 8. Educación religiosa y espacios. Sección 9. Aspectos Jurídicos.El presente texto reúne los aportes de muchas personas que-desde diferentes países del continente-desean contribuir a la revisión y transformación intercultural de la educación religiosa en Latinoamérica y el Caribe. Como lo sugiere el título, confluyen aquí reflexiones y voces plurales para caminos pedagógicos interculturales. Cada una de las "voces" que conforman este texto expresa la intención de promover una educación liberadora-intercultural-decolonial, a partir de los desafíos que reconocemos en la realidad latinoamericana-caribeña.This text brings together the contributions of many people who-from different countries of the continent-wish to contribute to the revision and intercultural transformation of religious education in Latin America and the Caribbean. As the title suggests, reflections and plural voices converge here for intercultural pedagogical paths. Each one of the "voices" that make up this text expresses the intention of promoting a liberating-intercultural-decolonial education, based on the challenges that we recognize in the Latin American-Caribbean reality.Universidad Bíblica Latinoamericana, FONAPER, Foro de Educación Religiosa Costarricense, Universidad Regional de Blumenau, UNOCHAOECÓ, Escuela Ecuménica de Ciencias de la ReligiónEscuela Ecuménica de Ciencias de la Religió

Complementary Sex Determination in the Parasitic Wasp Diachasmimorpha longicaudata

We studied the sex determination in Diachasmimorpha longicaudata, a parasitoid braconid wasp widely used as biological control agent of fruit pest tephritid flies. We tested the complementary sex determination hypothesis (CSD) known in at least 60 species of Hymenoptera. According to CSD, male or female development depends on the allelic composition of one sex locus (single-locus CSD) or multiple sex loci (multiple-locus CSD). Hemizygote individuals are normal haploid males, and heterozygotes for at least one sex locus are normal diploid females, but homozygotes for all the sex loci are diploid males. In order to force the occurrence of diploid males in D. longicaudata, we established highly inbred lines and examined their offspring using chromosome counting, flow cytometry, and sex ratio analysis. We found that when mother-son crosses were studied, this wasp produced about 20% of diploid males out of the total male progeny. Our results suggest that this parasitoid may represent the second genus with multiple-locus CSD in Hymenoptera. Knowledge about the sex determination system in D. longicaudata is relevant for the improvement of mass rearing protocols of this species. This information also provides the necessary background for further investigations on the underlying molecular mechanisms of sex determination in this species, and a better insight into the evolution of this pathway in Hymenoptera in particular and insects in general