Irma Vila

Estado de conocimiento de los peces dulceacuícolas de Chile

La ictiofauna nativa de los sistemas limnicos de Chile se compone de 11 familias, 17 generos y alrededor de 44 especies, incluyendo dos lampreas. De estas, 81% son endemicas de la provincia biogeografica chilena y 40% se encuentran clasificadas en peligro de extincion. Los grupos mas representados corresponden a los ordenes Siluriformes (11 especies), Osmeriformes (9 especies) y Atheriniformes (7 especies). Tambien estan representados en Chile los ciclostomos Petromyzontiformes (2 especies), y los teleosteos Characiformes (4 especies), Cyprinodontiformes (6 especies), Perciformes (4 especies) y Mugilifromes (1). Latitudinalmente, la mayor riqueza de especies ocurre en la zona centro-sur de la provincia Chilena, en tanto que los extremos norte y sur son de baja riqueza especifica. Dado su origen, porcentaje de endemismo y retencion de caracteres primitivos, este conjunto ictiofaunistico es de alto valor biogeografico y de conservacion. Existen sin embargo importantes vacios de conocimiento sobre su sistematica, distribucion y biologia.

Cyanobacterial diversity in Salar de Huasco, a high altitude saline wetland in northern Chile: an example of geographical dispersion?

The diversity of Cyanobacteria in water and sediment samples from four representative sites of the Salar de Huasco was examined using denaturing gradient gel electrophoresis and analysis of clone libraries of 16S rRNA gene PCR products. Salar de Huasco is a high altitude (3800 m altitude) saline wetland located in the Chilean Altiplano. We analyzed samples from a tributary stream (H0) and three shallow lagoons (H1, H4, H6) that contrasted in their physicochemical conditions and associated biota. Seventy-eight phylotypes were identified in a total of 268 clonal sequences deriving from seven clone libraries of water and sediment samples. Oscillatoriales were frequently found in water samples from sites H0, H1 and H4 and in sediment samples from sites H1 and H4. Pleurocapsales were found only at site H0, while Chroococcales were recovered from sediment samples of sites H0 and H1, and from water samples of site H1. Nostocales were found in sediment samples from sites H1 and H4, and water samples from site H1 and were largely represented by sequences highly similar to Nodularia spumigena. We suggest that cyanobacterial communities from Salar de Huasco are unique - they include sequences related to others previously described from the Antarctic, along with others from diverse, but less extreme environments.

Diversity of Bacteroidetes in high-altitude saline evaporitic basins in northern Chile

The phylum Bacteroidetes represents one of the most abundant bacterial groups of marine and freshwater bacterioplankton. We investigated the diversity of Bacteroidetes in water and sediment samples from three evaporitic basins located in the highlands of northern Chile. We used both 16S rRNA gene clone libraries created with targeted Bacteroidetes-specific primers and separation of specifically amplified gene fragments by denaturing gradient gel electrophoresis (DGGE). DGGE analysis revealed a reduced richness of these organisms in samples from Salar de Huasco (two to four DGGE bands) increasing in Salar de Ascotan (two to seven DGGE bands) and Laguna Tebenquiche at Salar de Atacama (four to eight DGGE bands). Cluster analysis (WPGMA) of DGGE bands showed that bands from Salar de Huasco and Salar de Ascotan grouped together and samples from Salar de Atacama formed separate clusters in water and sediment samples, reflecting different Bacteroidetes communities between sites. Most of the sequences analyzed belonged to the family Flavobacteriaceae and clustered with the genera Psychroflexus, Gillisia, Maribacter, Muricauda, Flavobacterium, and Salegentibacter. The most abundant phylotype was highly related to Psychroflexus spp. and was recovered from all three study sites. The similarity of the analyzed sequences with their closest relatives in GenBank was typically <97% and notably lower when compared with type strains, demonstrating the unique character of these sequences. Culture efforts will be necessary to get a better description of the diversity of this group in saline evaporitic basins of northern Chile.

Ecotoxicity assessment of metals and wastewater using multitrophic assays

Multitrophic test batteries are not yet widely used in toxicity testing although there is a growing tendency towards their usage. The aim of this study was to assess which are the most appropriate assays to include in a battery for monitoring ecotoxicity derived from heavy metals and wastewater. The tests applied that made up the battery were Bacillus cereus, Hydra attenuata, Panagrellus redivivus, Daphnia magna, Lactuca sativa, and Oncorhynchus mykiss, which were each used to determine acute and chronic toxicity, and mutagenicity under different samples (treatments) that included the following metals: Cd(II), Cu(II), Cr(VI), Hg(II). With the exception of O. mykiss, the same organisms were tested for ecotoxicity effects under wastewater samples derived from different processes of domestic and industrial effluents. Bioassays used were effective and delivered reproducible and reliable results. Most of the organisms chosen were sensitive to toxicants: O. mykiss and H. attenuata were the most sensitive species, while B. cereus was highly resistant to the chemicals. H. attenuata proved to be the most sensitive species with the environmental samples, while B. cereus and L. sativa were the most consistently resistant. The results led us to conclude that the battery was appropriate, allowing decisions to be made on the best tests depending on the type of contaminant, sensitivity required, and cost. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 370–375, 2000

Cyanobacterial diversity in Salar de Huasco, a high altitude saline wetland in Northern Chile, are highly similar to Antarctic cyanobacteria

The diversity of Cyanobacteria in water and sediment samples from four representative sites of the Salar de Huasco was examined using denaturing gradient gel electrophoresis and analysis of clone libraries of 16S rRNA gene PCR products. Salar de Huasco is a high altitude (3800 m altitude) saline wetland located in the Chilean Altiplano. We analyzed samples from a tributary stream (H0) and three shallow lagoons (H1, H4, H6) that contrasted in their physicochemical conditions and associated biota. Seventy-eight phylotypes were identified in a total of 268 clonal sequences deriving from seven clone libraries of water and sediment samples. Oscillatoriales were frequently found in water samples from sites H0, H1 and H4 and in sediment samples from sites H1 and H4. Pleurocapsales were found only at site H0, while Chroococcales were recovered from sediment samples of sites H0 and H1, and from water samples of site H1. Nostocales were found in sediment samples from sites H1 and H4, and water samples from site H1 and were largely represented by sequences highly similar to Nodularia spumigena. We suggest that cyanobacterial communities from Salar de Huasco are unique - they include sequences related to others previously described from the Antarctic, along with others from diverse, but less extreme environments.

Unique clusters of Archaea in Salar de Huasco, an athalassohaline evaporitic basin of the Chilean Altiplano

Analyses of clone libraries from water and sediments of different sites from Salar de Huasco, a high-altitude athalassohaline wetland in the Chilean Altiplano, revealed the presence of five unique clusters of uncultured Archaea that have not been previously reported or specifically assigned. These sequences were distantly related (83-96% sequence identity) to a limited number of other clone sequences and revealed no identity to cultured Archaea. The abundance of Archaea and Bacteria was estimated using qPCR and community composition was examined through the construction of clone libraries of archaeal 16S rRNA gene. Archaea were found to be dominant over Bacteria in sediments from two saline sites (sites H4: 6.31 x 10(4) and site H6: 1.37 x 10(4) microS cm(-1)) and in one of the water samples (freshwater from site H0: 607 muS cm(-1)). Euryarchaeotal sequences were more abundant than crenarchaeotal sequences. Many of the clone sequences (52%) were similar to uncultured archaeal groups found in marine ecosystems having identity values between 99% and 97%. A major fraction of the sequences (40%) were members of Methanobacteria, while others were included in the Marine Benthic Groups B and D, the Miscellaneous Crenarchaeotic Group, the Terrestrial Miscellaneous Euryarchaeotal Group, Marine Group I and Halobacteria. The presence of uncultured archaeal groups in Salar de Huasco extends their known distribution in inland waters, providing new clues about their possible function in the environment.

Bacterial and archaeal diversity in high altitude wetlands of the Chilean Altiplano

The microbial diversity of five unconnected high altitude (≥ 3800 m a.s.l.) wetlands from the Chilean Altiplano was analyzed by a culture-independent approach, using 16 S rRNA gene sequences of different microbial groups. The wetlands (Chungara Lake, Parinacota wetland, Piacota Lake, Salar de Huasco and Salar de Ascotan) differed in terms of habitat type and physicochemical properties. The bacterial communities of these systems were dominated by Bacteroidetes (24-94 % of the clones) and Proteobacteria (Alpha, Beta, Gamma and Delta subgroups) with smaller contributions by the Firmicutes, Actinobacteria, Planctomycetes, Verrucomicrobia, Chloroflexi, Cyanobacteria, Acidobacteria, Deinococcus-Thermus and Candidate Division WS3. Fourteen phylotypes matching Alphaproteobacteria were part of the marine Roseobacter clade, representing new clusters of this group. Archaeal diversity was much lower than that seen for bacteria, and was dominated by Euryarchaeota; however Crenarchaeota were also present. Considering the large differences in microbial community composition between sites and samples, the presence of eleven phylotypes common to two or more habitats is highlighted. The frequent presence of new taxa in different phylogenetic groups in the altiplanic wetlands studied here revealed the unique characteristics of Bacteria and Archaea in these fragile Andean ecosystems.

Microbial eukaryote plankton communities of high-mountain lakes from three continents exhibit strong biogeographic patterns.

Microbial eukaryotes hold a key role in aquatic ecosystem functioning. Yet, their diversity in freshwater lakes, particularly in high‐mountain lakes, is relatively unknown compared with the marine environment. Low nutrient availability, low water temperature and high ultraviolet radiation make most high‐mountain lakes extremely challenging habitats for life and require specific molecular and physiological adaptations. We therefore expected that these ecosystems support a plankton diversity that differs notably from other freshwater lakes. In addition, we hypothesized that the communities under study exhibit geographic structuring. Our rationale was that geographic dispersal of small‐sized eukaryotes in high‐mountain lakes over continental distances seems difficult. We analysed hypervariable V4 fragments of the SSU rRNA gene to compare the genetic microbial eukaryote diversity in high‐mountain lakes located in the European Alps, the Chilean Altiplano and the Ethiopian Bale Mountains. Microbial eukaryotes were not globally distributed corroborating patterns found for bacteria, multicellular animals and plants. Instead, the plankton community composition emerged as a highly specific fingerprint of a geographic region even on higher taxonomic levels. The intraregional heterogeneity of the investigated lakes was mirrored in shifts in microbial eukaryote community structure, which, however, was much less pronounced compared with interregional beta‐diversity. Statistical analyses revealed that on a regional scale, environmental factors are strong predictors for plankton community structures in high‐mountain lakes. While on long‐distance scales (>10 000 km), isolation by distance is the most plausible scenario, on intermediate scales (up to 6000 km), both contemporary environmental factors and historical contingencies interact to shift plankton community structures.

Phylogenetic and phylogeographic analysis of the genus Orestias (Teleostei: Cyprinodontidae) in the southern Chilean Altiplano: the relevance of ancient and recent divergence processes in speciation

This study presents phylogenetic molecular data of the Chilean species of Orestias to propose an allopatric divergence hypothesis and phylogeographic evidence that suggests the relevance of abiotic factors in promoting population divergence in this complex. The results reveal that diversification is still ongoing, e.g. in the Ascotán salt pan, where populations of Orestias ascotanensis restricted to individual freshwater springs exhibit strong genetic differentiation, reflecting putative independent evolutionary units. Diversification of Orestias in the southern Altiplano may be linked to historical vicariant events and contemporary variation in water level; these processes may have affected the populations from the Plio-Pleistocene until the present.

Contrasting population genetic structure of two widespread aquatic insects in the Chilean high-slope rivers

Dispersal and many other factors affect population genetic structure. In central Chile, rivers are characterised by strong currents and transverse mountain chains, which impose physical barriers to the populations that inhabit them. The objective of the present study was to study the population genetic structure of two widespread species of aquatic insects, the caddisfly Smicridea annulicornis and the mayfly Andesiops torrens, in three isolated rivers, Choapa, Maipo and Maule. The analysis of population structure, using both mtDNA (cytochrome C oxidase subunit 1, COI) and nuclear markers (amplified fragment length polymorphism, AFLP), considered samples from within and among rivers. In S. annulicornis, we found differentiation within and among rivers, indicating a low dispersal among the study area. Populations of A. torrens shared haplotypes in all three rivers and no differences were found among rivers, indicating that this species probably has more dispersal potential than does S. annulicornis; however, significant differences were observed within rivers. Our results indicate that the transverse mountain chains are not a barrier for A. torrens, which can disperse among rivers. Within rivers, the population structure suggests that these species are probably adapted to avoid drift because of the torrential character of these Chilean rivers.