Presencia de Gambusia affinis (Baird & Girard, 1853) en un humedal boscoso del Sur de Chile. Posibles implicancias sobre la fauna local de invertebrados.

Las especies invasoras son la principal causa de pérdida de biodiversidad del planeta, producto de la depredación que afecta a la fauna local mediante competencia, hibridación, alteración del hábitat y transmisión de enfermedades. En este estudio se describe la posible implicancia del pez mosquito sobre la fauna de invertebrados en un humedal boscoso presente en la región de la Araucanía, Chile. Los resultados nos indican la presencia de Gambusia affinis en todos los sitios de muestreo, destacándose su gran adaptabilidad a la temperatura y pH. El rol depredador de Gambusia affinis sobre mosquitos, puede favorecer al desarrollo de sus larvas, al consumir invertebrados predadores de éstas, influyendo en la estructura trófica de las comunidades. Palabras claves: Humedal boscoso, Gambusia affinis, Invasión, Depredació

Caracterización fisicoquímica del agua del estero Nonguén y su confluencia con el río Andalién, región del Biobío. Variación en relación a los distintos usos de suelo en su cuenca.

La cuenca del estero Nonguén es un ejemplo de la realidad que se observa en la mayoría de las cuencas localizadas en zonas urbanas, debido al alto grado de intervención que presenta en su parte baja, influenciada por el constante aumento de la alta densidad poblacional. Sin embargo, en su parte alta aún es posible observar sitios con muy poca intervención que permiten la conservación de ecosistemas acuáticos en condiciones relativamente prístinas. Se realizó una caracterización fisicoquímica del agua del estero Nonguén y de la zona de confluencia con el río Andalién. Los resultados mostraron que la parte alta de la cuenca presenta aguas de muy buena calidad, pero en la parte baja, a medida que la actividad urbana comienza a ser más intensa, esta calidad comienza a disminuir mostrando condiciones fisicoquímicas completamente distintas a las demás zonas evaluadas (ANOSIM, parwise test R = 1; p = 0.333). Palabras clave: calidad de agua, contaminación, cuenca

Descomposición de hojarasca de especies nativas y exóticas en un humedal boscoso de agua dulce de Chile

Decomposition of leaf litter is a fundamental process for the functioning of forested wetlands. The rapid increment of forest plantations has involved a greater contribution of leaf litter of exotic origin to these ecosystems. The decomposition rate between leaf litter of native and exotic origin in a forested wetland of the Mediterranean zone of Chile was compared, as well as the contribution of bacteria and macroinvertebrate to this process. It was determined that the decomposition rate of the leaf litter presented signifi cant differences (p < 0.05) between species, being faster in those of non-native origin. This could be due to differences in ecophysiological aspects of the leaves like the presence of chemical compounds such as waxes or oils. Both analyzed communities were relevant in the studied process. However, bacteria contributed mostly to the decomposition of both types of leaves. The implications of the physical and chemical characteristics of the leaves and the water on the processing of the foliar material are discussed.En los humedales boscosos, la descomposición de la hojarasca es un proceso fundamental para su funcionamiento. El rápido incremento de las plantaciones forestales ha implicado un mayor aporte de hojarasca de origen exótico a estos ecosistemas. Se comparó la tasa de descomposición entre hojarasca de origen nativo y exótico en un humedal boscoso de la zona Mediterránea de Chile, así como la contribución de las bacterias y macroinvertebrados a este proceso. Se determinó que la tasa de descomposición de la hojarasca presentó diferencias signifi cativas entre las diferentes especies (p < 0,05), siendo más rápido en especies de origen exótico. Esto podría ser dado por diferencias en algunos aspectos ecofi siológicos de las hojas como la presencia de compuestos químicos tales como ceras o aceites. Ambas comunidades analizadas fueron relevantes en el proceso estudiado. Sin embargo, las bacterias contribuyeron mayormente a la descomposición de ambos tipos de hojas. Se discuten las implicaciones de las características físicas y químicas de las hojas y el agua en el procesamiento del material foliar

Resource-allocation tradeoffs in caddisflies facing multiple stressors

The replacement of native forests by exotic tree monocultures, such as those of Eucalyptus, decreases the quality of leaf litter inputs to streams and often reduces riparian cover, which can elevate water temperature. The combined effects of these stressors on the survival and performance of detritivores may be important, as detritivore species loss leads to reduced litter breakdown, a key ecosystem process. Potential loss of cased caddisfly larvae is of particular concern because they are the predominant detritivores in many streams, they are sensitive to warming, and they expend energy on building and carrying their cases, which may be an added burden under times of stress. In a microcosm experiment, we tested whether (i) poor-quality Eucalyptus globulus litter impaired case construction by larvae of Sericostoma pyrenaicum (due to preferential allocation of the scarcer available energy to larval fitness) compared to high-quality Alnus glutinosa litter; (ii) whether this effect was enhanced by higher temperatures (15 vs. 10 degrees C) resulting in faster metabolism and greater energy expenditure; but (iii) reduced in the presence of chemical cues from a predatory fish (due to greater investment in more protective cases). We found that Eucalyptus had lethal and sublethal effects on larval caddisflies, increasing mortality, reducing growth, and impairing case construction, compared to larvae fed Alnus. Temperature did not reinforce the effects of exotic litter on case construction, but predator chemical cues triggered the construction of more protective cases (i.e., longer and better cemented) despite the lower resource quality, providing evidence for environmentally mediated resource-allocation tradeoffs

Una clasificación edafológica, morfológica y climática de humedales boscosos de agua dulce de Chile

Wetlands of the same kind can present considerable difference in relation to a series of environmental variables that influence on the physicochemical properties and on the biological communities sustained, natural variability scarcely considered in comparative studies. The aim of this work was to provide a first approach to the edaphological, morphological and climatic classification of the forested wetlands from central Chile, unique environments for the conservation of an interesting floral and faunal diversity. 18 wetlands were classified in the Araucanía Region, by means of the B classification procedure by the European Union Water Framework Directive. 21 variables at basin scale were used. Four ecotypes were obtained, which were characterized mainly by microclimates and soil types, though were also relevant morphological variables such as slope, slope of the wetlands, and the basins towards they drain (Wilks’s Lambda < 0.193, F > 3.84). Ecotypes determined were defined by: 1) convergence of moderate marine, warm and Mediterranean climates with silty clay loam soil and high slopes, 2) moderate marine climate with silty loam soil and high slopes, 3) Cold Mediterranean climate with silty loam soil and low slopes and 4) Moderate marine climate, silty clay loam soil and high slope. Classification is in agreement with in situ observations. Nevertheless, it must be validated by both limnological and biological approaches.Humedales del mismo tipo pueden presentar diferencias considerables en relación a una serie de variables ambientales que influyen en las propiedades fisicoquímicas y a su vez en las comunidades biológicas que sustentan. Sin embargo, en estudios comparativos, esta variabilidad natural es generalmente poco considerada. El objetivo de este trabajo fue realizar una primera aproximación de una clasificación edafológica, morfológica y climática de los humedales boscosos de la zona central de Chile, ecosistemas únicos para la conservación de una interesante diversidad de flora y fauna. Se clasificaron 18 humedales presentes en la región de la Araucanía, mediante el procedimiento de clasificación B de la Directiva Marco del Agua de la Unión Europea, utilizando 21 variables a escala de cuenca. Se obtuvieron cuatro ecotipos, caracterizados principalmente por el microclima y tipo de suelo, aunque también fueron relevantes variables morfológicas, como la pendiente y la superficie de sus cuencas (Lambda de Wilks <0,193, F> 3,84). Los ecotipos determinados estuvieron definidos por: 1) Convergencia de climas marino fresco, cálido y mediterráneo frio, con suelo franco arcillo limoso y pendientes altas, 2) Clima marino fresco con suelo franco limoso y pendientes altas, 3) Clima mediterráneo frio con suelo franco limosos y pendientes bajas y 4) Clima marino fresco, suelo franco arcillo limoso y pendiente alta. La clasificación debe ser posteriormente validada mediante observaciones in situ de variables limnológicas y biológicas

Efectos de una zona urbana sobre la comunidad de macroinvertebrados bentónicos de un ecosistema fluvial del sur de Chile

Un cuerpo de agua dulce saludable puede proveer de numerosos beneficios a la sociedad, aunque actualmente la degradación de este tipo de ecosistemas se ha visto incrementada por el establecimiento de centros urbanos en sus riberas. En este estudio analizamos el efecto espacial de estas zonas sobre la calidad del agua, utilizando la comunidad de macroinvertebrados bentónicos como bioindicadores de contaminación fluvial en el canal Gibbs de la comuna de Temuco (38° 46' S 72° 38' W). Los muestreos fueron realizados en la época de primavera en seis sitios. El macrozoobentos estuvo compuesto por un total de 15 taxones, correspondientes a organismos tolerantes a condiciones de anoxia y a altas concentraciones de materia orgánica, tales como anfípodos (RyaleIla), dípteros (Quironomidae) y oligoquetos (Oligochaeta). Hubo una marcada diferencia en la composición y abundancia de taxones entre las zonas pre-urbana, urbana y post-urbana (ANOS1M R Global = 0.882; P = 0.001), tendencia que también fue registrada por los parámetros fisicoquímicos (ANOS1M R Global = 0.498; p = 0.001), de los cuales el pH, sólidos suspendidos totales y oxígeno disuelto son los que mejor explicaron los patrones observados en el macrozoobentos. Los resultados obtenidos con el índice biótico de familias (ChIBF) fueron similares a los registrados en las partes bajas de las cuencas del Sur de Chile y la comunidad de invertebrados demostró ser sensible a perturbaciones de origen antrópico.A healthy body of freshwater can provide numerous benefits to the society, although currentIy, the degradation of such ecosys­tems has been increased due to the establishment of urban areas along its riverbanks. In this study we analyzed the spatial effect of these zones on the water quality, using the benthonic macroinvertebrate communities as bioindicators of fluvial con­tamination in the Gibbs channel ofthe Temuco commune (38°46'S n038'W). The samplings were performed in spring, in six sites. The macrozoobentos was composed by a total of 15 taxa, corresponding to organisms tolerant to anoxic conditions and high concentrations of organic matter, such as amphipods (Hyalella), dipterans (Quironomidae), and oligochaetes (Oligochae­ta). There was a marked difference in the composition and abundance of taxa between the pre-urban, urban, and post-urban areas (ANOSIM Global R = 0.882,p = 0.001) tendency that was also recorded by the physicochemical parameters (ANOS 1M Global R = 0.498, p = 0.001), of which pR, total suspended solids, and dissolved oxygen are those that best explained the patterns observed in the macrozoobentos. The results obtained with the biotic family index (ChIBF) were similar to those registered in the lower parts of the basins of southern Chile and the invertebrate community was shown to be sensitive to anthropogenic disturbances

Extreme temperature events alter stream ecosystem functioning

Extreme temperature events have increased in intensity, duration and frequency in the last century, with potential consequences on organisms and ecosystems. In many streams, leaf litter of terrestrial origin is a key resource for microorganisms and some detritivores, and its decomposition has a main role on ecosystem functioning and is often used as an indicator of ecological integrity. As litter is often exposed to atmospheric conditions before entering the stream, extreme warming and freezing events may alter its physicochemical structure and affect decomposition and associated detritivores. We tested this prediction in a microcosm experiment by exposing litter of three tree species (in single-species treatments and the 3-species mixture) to different temperature pre-treatments: heating (40 degrees C), freezing ( - 20 degrees C) and both (heating followed by freezing). We then examined changes in litter traits due to leaching (72 h), litter decomposition in the absence and presence of detritivores, and detritivore growth (28 d), with focus on mass and nutrient (nitrogen and phosphorus) changes. Nutrient leaching was promoted mostly by the heating pre-treatment, which apparently produced lower-quality litter. However, microbial activity mostly resulted in litter mass and nutrient gain, which were reinforced by the heating pre-treatment, while freezing had the opposite effect. When detritivores were present, decomposition showed high variation among litter types but, again, the heating and freezing pre-treatments tended to reduce and enhance nutrient loss, respectively. The greatest and more consistent effects occurred for detritivore growth, which was reduced by temperature pre-treatments, particularly in the highest-quality litter type. In general, the sequential application of heating and freezing pre-treatments showed no synergistic effect, and the litter mixture showed similar responses to single-species treatments. Our results demonstrate that short-term extreme temperatures can modify litter quality in riparian soils and have subsequent effects on its decomposition within the stream and associated fauna, potentially altering stream food webs, ecosystem functioning and biogeochemical cycles.This study was funded by the Spanish Ministry for Science, Innovation and Universities and FEDER (project BioLoss, Ref. RTI2018-095023-B400), Basque Goverment funds (Ref. IT951-16) and Initiation Fondecyt Project (Ref. 11170390). I. Diaz and U. Apodaka-Etxebarria contributed to the sample processing

Impacts of fragmentation on floristic composition of swamp forests in south-central Chile

Los bosques pantanosos del centro-sur de Chile han sido fuertemente alterados por la fragmentación del paisaje, derivada principalmente de actividades antrópicas. A pesar de su alto valor ecológico y de conservación para la biodiversidad, estos ecosistemas han sido poco estudiados. El objetivo de este estudio fue evaluar la riqueza de plantas vasculares en distintos fragmentos de bosque pantanoso de la región de La Araucanía (38° S, Chile). Se estudiaron 11 fragmentos en total, en los cuales se definieron zonas de borde y núcleo. Se levantaron transectos florísticos y se identificaron todas las especies de plantas vasculares. Se determinaron diferencias en la composición florística entre el borde y núcleo, y se realizó un GLM para modelar la respuesta de la riqueza de especies en función de la superficie de los fragmentos y el origen geográfico de las plantas. Los resultados mostraron un total de 123 especies de plantas, de las cuales 76 son nativas y 47 son no-nativas. La composición florística difiere significativamente entre zonas de borde y núcleo, y la riqueza de especies está influenciada por la superficie de los fragmentos y el origen geográfico de las plantas. Nuestro estudio concluye que el tamaño de los fragmentos y las características de la matriz circundante son variables fundamentales que influencian la composición florística de los bosques pantanosos en el centro-sur de ChileThe swamp forests of south-central Chile have been greatly altered by the fragmentation of the landscape, which is mainly derived from anthropogenic activities. Despite their high ecological and conservation value for the biodiversity, these ecosystems have been scarcely studied. The main goal of this study was to evaluate the richness of vascular plants in different fragments of swamp forests in the Araucania region (38 degrees S, Chile). A total of 11 fragments were studied, in which edge and core zones were defined. Floristic transects were established, and we recorded and identified all species of vascular plants. Differences in the floristic composition between the edge and the core zones were determined, and we performed a GLM to model the response of species richness according to the area of the fragments and the geographical origin of the plants. A total of 123 species of plants were found across all fragments, of which 76 were native and 47 were non-native species. The floristic composition differs significantly between edge and core zones, and the GLM revealed that species richness is influenced by the area of the fragments and the geographical origin of the plants. Our study concludes that the size of the fragments, as well as by the characteristics of the surrounding matrix are fundamental variables that influence the floristic composition of swamp forests in south-central Chil

Effects of gamma irradiation on instream leaf litter decomposition

Leaf litter decomposition is a key process in stream ecosystems, the rates of which can vary with changes in litter quality or its colonization by microorganisms. Decomposition in streams is increasingly used to compare ecosystem functioning globally, often requiring the distribution of litter across countries. It is important to understand whether litter sterilization, which is required by some countries, can alter the rates of decomposition and associated processes. We examined whether litter sterilization with gamma irradiation (25 kGy) influenced decomposition rates, litter stoichiometry, and colonization by invertebrates after weeks of instream incubation within coarse-mesh and fine-mesh litterbags. We used nine plant species from three families that varied widely in litter chemistry but found mostly consistent responses, with no differences in decomposition rates or numbers of invertebrates found at the end of the incubation period. However, litter stoichiometry differed between irradiated and control litter, with greater nutrient losses (mostly phosphorus) in the former. Therefore, the effects of irradiation on litter chemistry should be taken into account in studies focused on stoichiometry but not necessarily in those focused on decomposition rates, at least within the experimental timescale considered here

Freshwater biodiversity and conservation in mediterranean climate streams of Chile.

In Chile, mediterranean climate conditions only occur in the Central Zone (ChMZ). Despite its small area, this mediterranean climate region (med-region) has been recognised as a hotspot for biodiversity. However, in contrast to the rivers of other med-regions, the rivers in the ChMZ have been studied infrequently, and knowledge of their freshwater biodiversity is scarce and fragmented. We gathered information on the freshwater biodiversity of ChMZ, and present a review of the current knowledge of the principal floral and faunal groups. Existing knowledge indicates that the ChMZ has high levels of endemism, with many primitive species being of Gondwanan origin. Although detailed information is available on most floral groups, most faunal groups remain poorly known. In addition, numerous rivers in the ChMZ remain completely unexplored. Taxonomic specialists are scarce, and the information available on freshwater biodiversity has resulted from studies with objectives that did not directly address biodiversity issues. Research funding in this med-region has a strong applied character and is not focused on the knowledge of natural systems and their biodiversity. Species conservation policies are urgently required in this highly diverse med-region, which is also the most severely impacted and most populated region of the country