Efecto de la introducción de peces en la conservación de anfibios y crustáceos de lagos de alta montaña

Este capítulo contiene 16 páginas, 11 figuras y una tabla.La introducción de especies invasoras es un aspecto determinante relacionado con el cambio global que incide en la conservación de los ecosistemas. Actualmente, la gestión para la conservación (e.g., Parques Nacionales) se enfrenta a las incertidumbres creadas con la aparición de nuevas especies introducidas por el hombre, sobre todo las que pasan a desarrollar un papel clave en los ecosistemas. Para poder tomar políticas de gestión correctas es necesario conocer con detalle cuál es el impacto de estas especies y su papel en el ecosistema. Los lagos del Parque Nacional de Aigüestortes y Estany de Sant Maurici han sufrido la introducción de peces llegando a tener en la actualidad un 62% de lagos afectados. El objetivo general del proyecto fue estudiar el efecto de la introducción de peces en las comunidades planctónicas y bentónicas de los lagos de alta montaña del Parque Nacional. Para llevar a cabo tal objetivo nos centramos en el estudio de dos grupos de organismos indicadores, los crustáceos del plancton y los anfibios. Los resultados obtenidos nos muestran que los peces son el factor principal que explica la presencia de la mayor parte de las especies de anfibios en los lagos. En cambio el efecto de los peces sobre la presencia de crustáceos planctónicos se limita a las especies de mayor tamaño, afectando principalmente la biodiversidad y especialmente la abundancia de los crustáceos, que disminuye con la presencia de peces. La desaparición de los anfibios en los lagos con peces provoca un efecto en cascada cambiando biomasa y composición de las algas y procariotas (bacterias y arqueas) que viven en la superfície de las piedras del litoral de los lagos.Peer reviewe

Discovering hidden biodiversity: the use of complementary monitoring of fish diet based on DNA barcoding in freshwater ecosystems

Ecological monitoring contributes to the understanding of complex ecosystem functions. The diets of fish reflect the surrounding environment and habitats and may, therefore, act as useful integrating indicators of environmental status. It is, however, often difficult to visually identify items in gut contents to species level due to digestion of soft-bodied prey beyond visual recognition, but new tools rendering this possible are now becoming available. We used a molecular approach to determine the species identities of consumed diet items of an introduced generalist feeder, brown trout (Salmo trutta), in 10 Tasmanian lakes and compared the results with those obtained from visual quantification of stomach contents. We obtained 44 unique taxa (OTUs) belonging to five phyla, including seven classes, using the barcode of life approach from cytochrome oxidase I (COI). Compared with visual quantification, DNA analysis showed greater accuracy, yielding a 1.4-fold higher number of OTUs. Rarefaction curve analysis showed saturation of visually inspected taxa, while the curves from the DNA barcode did not saturate. The OTUs with the highest proportions of haplotypes were the families of terrestrial insects Formicidae, Chrysomelidae, and Torbidae and the freshwater Chironomidae. Haplotype occurrence per lake was negatively correlated with lake depth and transparency. Nearly all haplotypes were only found in one fish gut from a single lake. Our results indicate that DNA barcoding of fish diets is a useful and complementary method for discovering hidden biodiversity. In this paper sequence-based DNA barcoding was applied to determine the diet of a generalist predator (brown trout, Salmo trutta) based on gut analyses. Subsequently, the results were compared with data derived from visual inspection. Based on our results, we discuss the potential of using prey organisms in fish gut contents as a supplementary monitoring tool to reveal hidden biodiversity

The influence of microstructure on charge separation dynamics in organic bulk heterojunction materials for solar cell applications

Light-induced charge formation is essential for the generation of photocurrent in organic solar cells. In order to gain a better understanding of this complex process, we have investigated the femtosecond dynamics of charge separation upon selective excitation of either the fullerene or the polymer in different bulk heterojunction blends with well-characterized microstructure. Blends of the pBTTT and PBDTTPD polymers with PCBM gave us access to three different scenarios: either a single intermixed phase, an intermixed phase with additional pure PCBM clusters, or a three-phase microstructure of pure polymer aggregates, pure fullerene clusters and intermixed regions. We found that ultrafast charge separation (by electron or hole transfer) occurs predominantly in intermixed regions, while charges are generated more slowly from excitons in pure domains that require diffusion to a charge generation site. The pure domains are helpful to prevent geminate charge recombination, but they must be sufficiently small not to become exciton traps. By varying the polymer packing, backbone planarity and chain length, we have shown that exciton diffusion out of small polymer aggregates in the highly efficient PBDTTPD:PCBM blend occurs within the same chain and is helped by delocalization

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Interacción entre clima y ocupación humana en la configuración del paisaje vegetal del Parque Nacional de Aigüestortes i Estany de Sant Maurici a lo largo de los últimos 15.000 años

The vegetation of the National Park of Aigüestortes i Estany de St Maurici is the result of an interaction between climate, plant community dynamics and the human occupation of the territory. The OCUPAproject aimed to reconstruct this interaction across the last millennia combining methods from palaeoecology and archaeology. The study focused primarily on the Sant Nicolau valley and built on the multidisciplinary analysis of the sedimentary archive of two lakes (Llebreta and Redó) and a number of archaeological sites located in shelters and outdoors. There is archaeological evidence of human presencesince 9000 yr cal BP, and a continuous record since 7500 yr cal BP. At early stages, humans transformed the surroundings of the shelters occupied and lithic tools indicate contacts with locations far away (i.e.,the Ebro plains). Since more than 3000 years ago, there has been human impact on the vegetation withoutinterruption until present. Initially, the impacts were mostly related to livestock: use of fire to open grazing lands, soil erosion and, during the medieval period, forestry and eutrophication of lakes. The agriculture impact in the lower part of the valley (e.g., Llebreta) occurred about 2100 yr ago, although some cereal grains and tools for harvesting have been found for the Neolithic. In the medieval period, the impact was higher than during the last centuries. In general, the changes in the human land use approximately follow the major changes in climate, but the specific causal link is likely related to the social and cultural dynamics of a broader territory since the Neolithic

Rapid amphibian community recovery following removal of non-native fish from high mountain lakes

Amphibians of high mountain lakes face many threats related to global change, including novel pathogens, development, climate change and overexploitation. However, the foremost threat is the presence of non-native fish. One of the objectives of the LIFE+ LIMNOPIRINEUS project (2014–2019) was the recovery of protected amphibian communities (including the endemic Calotriton asper) in eight naturally fishless Pyrenean high mountain lakes, by controlling or eradicating non-native trout or minnows. During the summer months of 2015 to 2019, we removed 95–100% of the fish present in these lakes, and monitored changes in their amphibian populations, as well as surveyed 56 nearby control lakes with or without fish. We found rapid natural recovery of amphibian communities as fish removal work progressed. The fish-removal lakes achieved typical richness figures for the area one year after fish removal began, and typical species abundances after three years (with the only exception of Rana temporaria). We documented a total of 16 colonisation events, all by amphibian species from the same valley. The two earliest colonisation events were observed in the year in which fish removal began, with eight events the following year. The lack of colonisation from nearby valleys in the study period highlights the crucial role of nearby residual populations not affected by human impacts. We show that whole amphibian communities from high mountain lakes recover rapidly after eliminating or reducing non-native fish, proving that this is a powerful tool to improve the conservation status of endangered amphibians

Using invertebrate remains and pigments in the sediment to infer changes in trophic structure after fish introduction in Lake Fogo: a crater lake in the Azores

Fish introduction may have marked effects on the trophic dynamics and ecological state of former fishless lakes, but due to scarcity of historical data this can seldom be documented. We used remains of cladoceran, chironomid and pigment assemblages in the sediment archive to unravel the effect of introduction of carp (Cyprinus carpio), rainbow trout (Oncorhynchus mykiss) and a cyprinid (Chondrostoma oligolepis) in Lake Fogo, the Azores (Portugal). The stratigraphical record showed two major shifts in community assemblage coinciding with the time of introduction of carp (AD ca. 1890) and trout (AD 1941), respectively. Carp introduction was followed by an abrupt and major decline in the abundance of chironomids, a shift in the cladoceran community from a benthic to a more pelagic dominated community, and Daphnia size was significantly reduced. Pigment assemblages also indicated a shift from a benthic to a pelagic dominated ecosystem, as cryptophytes became markedly more abundant at the expense of benthic diatoms. Trout introduction was followed by a return to a more benthic cladoceran and benthic algae (pigments) dominated state, which we attribute to trout predation on carp leading to improved water clarity. A steady increase in the abundance of pigments and cladoceran remains followed, suggesting enhanced productivity, which may be attributed to enhanced atmospheric nitrogen deposition and introduction of C. oligolepis. We conclude that fish introduction has profoundly altered the trophic dynamics and the relative importance of benthic and pelagic production in this species poor and natural fishless lake in the Azores, and likely in most others lakes at the archipelago islands as fish stocking has been a widespread practice