Time filter

Source Type

Badano E.I.,San Luis Potosí Institute of Scientific Research and Technology | Marquet P.A.,Center for Advanced Studies in Ecology and Biodiversity | Marquet P.A.,University of Chile | Marquet P.A.,Santa Fe Institute | And 2 more authors.
Acta Oecologica | Year: 2010

Physical ecosystem engineering is the process by which some species change the distribution of materials and energy in ecosystems. Although several studies have shown that this process is a driver of local species diversity, the current challenge is predicting when and where ecosystem engineering will have large or small impacts on communities, while also explaining why impacts vary in magnitude across engineer species and environments. This study addresses this issue and proposes a series of predictions for these effects at the three spatial scales (the patch, the habitat and the landscape) along environmental gradients of physical stress. The integrative prediction of this study was that the difference in species diversity between engineered and unmodified situations (patches, habitats or landscapes) will increase as the difference in physical stress between engineered and unmodified patches becomes larger. To test the prediction, the effects of two well known high-Andean ecosystem engineers, the cushion plants Azorella madreporica and Laretia acaulis, were assessed on plant species richness in central Chile. The results support the main prediction, showing that ecosystem engineers have negative effects on species diversity at sites when the environmental modifications they perform increase physical stress for other species, while they have positive effects at sites where these habitat changes mitigate physical stress. Then, the effects of the ecosystem engineers on species diversity seem to depend on the environmental context, where larger environmental modifications are reflected in greater impacts, either positive or negative, on species diversity. © 2009 Elsevier Masson SAS. All rights reserved.

Figueroa D.P.,University of Chile | Sabat P.,University of Chile | Sabat P.,Center for Advanced Studies in Ecology and Biodiversity | Torres-Contreras H.,University of Chile | And 2 more authors.
Journal of Insect Physiology | Year: 2010

Small animals need efficient water conservation mechanisms for survival and reproduction, which is relevant for the spiders that have large book lungs with large respiratory surface. If lung evaporation is relevant to limit water loss, adjustments of the spiracle opening to metabolic demands should be expected. In this study, we measured the metabolic rate and total evaporative water loss mediated by the opening of the spiracles in the migalomorph spider Paraphysa parvula, a resident of fluctuating Mediterranean environments of the mountains of central Chile. We found that the metabolism of P. parvula was similar to other Theraphosidae and low compared to other arthropods. Carbon dioxide production and evaporative water loss increased with temperature, particularly at 40°C. The total evaporative water loss at 40°C increased dramatically to about 10 times that found with the lower temperatures. Thus, 40°C will be the limit temperature for this species after which evaporative water loss starts to become damaging, so it has to avoid it. The exposition to hypercapnic environments had as a consequence an increase in evaporative water loss and the involvement of the book lungs in this loss was about 60%. The possibility of losing water could condition this species to seek temperate and oxygenated shelters under rocks. © 2010 Elsevier Ltd.

Leroy F.,University Pierre and Marie Curie | Leroy F.,French National Center for Scientific Research | Comtet T.,University Pierre and Marie Curie | Brante A.,Catholic University of the Holy Conception | And 4 more authors.
Journal of Molluscan Studies | Year: 2012

Many marine gastropod species brood their embryos in thin-walled capsules to protect them during development. Despite its beneficial effects, encapsulation has two major constraints, nutrition and oxygen supply, which affect embryo development and larval survival. Developing embryos usually rely on intracapsular food sources provided by the mother, in the form of yolk, nurse eggs and intracapsular fluid. However, it is still not clear if they are able to feed on extracapsular sources that may cross the capsule wall. We investigated this possibility in the calyptraeid species Crepidula fornicata. In this species, the internal capsule wall thickness sharply decreases during embryonic development, which might change wall permeability to small organic molecules, thus providing embryos with external dissolved organic matter. To test this hypothesis, encapsulated and excapsulated embryos of C. fornicata were placed for 48 h in a 13C-enriched amino acid (l-alanine) solution. Excapsulated embryos were enriched in 13C (5.75‰), which suggested that they were able to assimilate the labelled amino acid. In contrast, encapsulated embryos were weakly enriched (0.75‰), suggesting that encapsulation greatly reduces the potential for the use of extracapsular amino acids and that encapsulated embryos mainly rely on maternal food. © 2011 The Author.

Contreras L.,Center for Advanced Studies in Ecology and Biodiversity | Moenne A.,University of Santiago de Chile | Gaillard F.,French National Center for Scientific Research | Potin P.,University Pierre and Marie Curie | Correa J.A.,Center for Advanced Studies in Ecology and Biodiversity
Aquatic Toxicology | Year: 2010

A proteomic analysis combining peptide de novo sequencing and BLAST analysis was used to identify novel proteins involved in copper tolerance in the marine alga Scytosiphon gracilis (Phaeophyceae). Algal material was cultivated in seawater without copper (control) or supplemented with 100 μg L-1 for 4 days, and protein extracts were separated by two-dimensional gel electrophoresis (2-DE). From the proteins obtained in the copper treatment, 25 over-expressed, 5 under-expressed and 5 proteins with no changes as compared with the control, were selected for sequencing. Tryptic-peptides obtained from 35 spots were analyzed by capillary liquid chromatography and tandem mass spectroscopy (capLC/MS/MS), and protein identity was determined by BLASTP. We identified 19 over-expressed proteins, including a chloroplast peroxiredoxin, a cytosolic phosphomannomutase, a cytosolic glyceraldehyde-3-phosphate dehydrogenase, 3 ABC transporters, a chaperonine, a subunit of the proteasome and a tRNA synthase, among others. The possible involvement of these over-expressed proteins in buffering oxidative stress and avoiding metal uptake in S. gracilis exposed to copper excess is discussed taking into consideration the information available for other plant models. © 2009 Elsevier B.V. All rights reserved.

Brante A.,Catholic University of the Holy Conception | Brante A.,International Laboratory Dispersal and Adaptation in Marine Species | Brante A.,Center for Advanced Studies in Ecology and Biodiversity | Fernandez M.,University of Santiago de Chile | And 6 more authors.
Journal of Heredity | Year: 2012

The biogeography and phylogeography concordance hypothesis suggests that the same factors, for instance physical barriers or environmental gradients, shape both species assemblages and intraspecific genetic structure. In the marine realm, previous studies have however suggested that phylogeographic patterns are also explained by the life-history strategy of the species. However, evidence is contradictory and comes mainly from the northern hemisphere, which is characterized by specific environmental conditions and evolutionary histories of species. In this work, we evaluated the concordance hypothesis in the southern Pacific using the marine gastropod Crepipatella dilatata as a case study. This intertidal species with direct development exhibited a restricted dispersal potential, a feature that contrasts with previous species studied in the same area. Using the gene cytochrome oxidase I, we analyzed 253 individuals sampled at 10 locations covering 543 km of the coast of Chile. The study sites also incorporated 2 biogeographic regions separated by a well-studied biogeographic break (at 30°S). Populations of C. dilatata displayed a high degree of genetic structure and a perfect match between phylogeographic and biogeographic breaks at 30°S. When comparing our data with previous research over the same geographic range, life history traits related to dispersal ability seem to be a good proxy for explaining the concordance between biogeography and phylogeography along the southeastern pacific coast. In addition, in this and other marine invertebrate species, gene flow limitations across both sides of the 30°S break may act as a driver of the speciation process. © 2012 The American Genetic Association. All rights reserved.

Lopez-Cristoffanini C.,Andrés Bello University | Lopez-Cristoffanini C.,Center for Advanced Studies in Ecology and Biodiversity | Tellier F.,Catholic University of the Holy Conception | Otaiza R.,Catholic University of the Holy Conception | And 2 more authors.
Botanica Marina | Year: 2013

Tolerance to air exposure should be an important feature in determining the geographic distribution of seaweeds. Two sibling kelp species with contrasting latitudinal distributions were selected to test the relationship between their distribution and air exposure tolerance: Lessonia berteroana distributed between 18° and 30°S and Lessonia spicata, which is found from 29° to 41°S along the Chilean coast. This region presents a latitudinal gradient of environmental variables, which leads to an increase in air exposure as latitude decreases. Therefore, populations of L. spicata are likely to be exposed to lower desiccation levels than those of L. berteroana. To assess adaptation to air exposure, early stages of development of these species were exposed to air daily for 0, 0.5, 1, and 2 h, and the activities of two antioxidant enzymes (ascorbate peroxidase and catalase) were measured. Results showed that L. spicata spores ceased their postgermination development when exposed to 1 and 2 h of air, contrasting with L. berteroana, in which spore development was not abruptly stopped as for L. spicata. In addition, the apparent inactivation of the antioxidant enzyme catalase in both species strongly suggests a lower buffering capacity to an excess of reactive oxygen species (ROS) triggered by air exposure. Thus, air exposure seems an important factor determining the northern geographic limit of L. spicata.

Contreras-Porcia L.,Center for Advanced Studies in Ecology and Biodiversity | Thomas D.,Center for Advanced Studies in Ecology and Biodiversity | Flores V.,Center for Advanced Studies in Ecology and Biodiversity | Correa J.A.,Center for Advanced Studies in Ecology and Biodiversity
Journal of Experimental Botany | Year: 2011

Unravelling the mechanisms underlying desiccation tolerance is crucial in order to understand the position of algal species in the intertidal zone. The alga Porphyra columbina lives in the uppermost part of the rocky intertidal zones around the world and was selected as a model for this study. Naturally desiccated plants were collected during low tide and studied for morphological changes, oxidative burst induction, biomolecule oxidation, antioxidant responses, and photosynthetic status. Naturally hydrated plants collected during high tides were used for comparative purposes. In addition, changes induced by desiccation were assessed in vitro and the capacity to recover from desiccation was determined by rehydrating the fronds in seawater. The global results show that desiccation induces morphological and cellular alterations accompanied by a loss of ∼96% of the water content. Overproduction of reactive oxygen species (ROS) was induced by desiccation and two peaks of H2O 2 were detected at 1 and 3 h of desiccation. However, during in vitro rehydration post-desiccation, the ROS quickly returned to the basal levels. At the biomolecular level, only a low production of oxidized proteins was recorded during desiccation, whereas the activity of diverse antioxidant enzymes increased. However, this activity diminished to near basal levels during rehydration. The photosynthetic efficiency (Fv/Fm) during desiccation declined by 94-96% of the values recorded in hydrated plants. This reduction was generated by the low levels of trapped energy flux per cross-section (TRo/CS), electron transport flux per CS (ETo/CS), and density of reaction centres (RC/SCo) as well as the chlorophyll content. The inverse pattern was observed for the levels of phycocyanin and phycoerythrin content. Fv/Fm and the photosynthetic indicators were restored to normal levels after only 5 min of rehydration. The results indicate that desiccation in P. columbina causes overproduction of ROS that is efficiently attenuated. The morphological and photosynthetic changes could be operating as tolerance mechanisms due to the fact that these responses principally prevent biomolecular alteration and cellular collapse. Thus, the activation of different physiological mechanisms helps to explain the high tolerance to desiccation of P. columbina and, at least in part, the position of this species at the highest level in the intertidal zone. © 2010 The Author(s).

Andrade S.,Center for Advanced Studies in Ecology and Biodiversity | Pulido M.J.,Center for Advanced Studies in Ecology and Biodiversity | Correa J.A.,Center for Advanced Studies in Ecology and Biodiversity
Chemosphere | Year: 2010

Copper complexation in marine systems is mainly controlled by organic matter, partially produced by micro- and macroalgae that release exudates with the capacity to bind metals. This feature is important as it influences bioavailability, bioaccumulation, toxicity, and transport of copper through biological membranes. The release of Cu-complexing ligands by seaweeds cultured under copper excess was studied in the laboratory. Five macroalgae belonging to different functional groups were used, including the filamentous Chaetomorpha firma (Chlorophyta), the foliose Ulva lactuca (Chlorophyta) and Porphyra columbina (Rhodophyta), the corticated Gelidium lingulatum (Rhodophyta), and the leathery Lessonia nigrescens (Phaeophyceae). The concentration of ligands and their copper-binding strength (log K′) of exudates released by each species was determined by anodic stripping voltammetry (ASV). The selected algae released exudates in a wide range of concentration (42-117 nM) after 48 h of culture, and addition of 157 nM copper increased the production of ligands up to 8 times. A relationship between structural complexity or thallus thickness and the amount of ligands released was not observed. The binding strength (log K′) varied among species from 7.6 to 8.9, a response that was not modified by exposure to sub-lethal copper excess. The kelp L. nigrescens showed a fast response to copper excess, releasing ligands that reduced toxicity of the metal in hours. Results suggest that intertidal and shallow subtidal macroalgae might have been overlooked regarding their role as producers of organic ligands and, therefore, as modulators of metal complexing capacity in coastal waters. © 2009 Elsevier Ltd. All rights reserved.

Castro S.A.,University of Santiago de Chile | Castro S.A.,Center for Advanced Studies in Ecology and Biodiversity | Badano E.,University of Concepción | Guzman D.,University of Santiago de Chile | Cavieres L.,University of Concepción
Biological Invasions | Year: 2010

In central Chile, the bur beak chervil (Anthriscus caucalis M. Bieb.; Apiaceae) is an annual naturalized herb introduced from Europe at least 120 years ago. Anthriscus is distributed in vegetation formations such as sclerophyllous shrublands (locally known as "matorral") and spiny savannas of Acacia caven (locally known as "espinal"). In matorral formations, Anthriscus grows at the edge of native woody fragments. Because these fragments are refuges where native herbs recruit, we studied the impact of Anthriscus on the diversity and survival of native forbs established in these sheltering microsites. First, we characterized the spatial distribution of Anthriscus in the matorral, sampling in different micro-habitat types. We differentiated three microhabitat types: under the canopy of a fragment, at the edge of the canopy of a fragment, and in open sites outside the fragments. A total of 40 1 × 1 m quadrates were randomly distributed in each habitat type. Inside each of them, we recorded the number of seedlings and established plants, including Anthriscus. Then we evaluated experimentally the effect of Anthriscus on diversity and evenness of the local herb assemblages. For this purpose we conducted a field trial using 34 metallic enclosures (0.5 × 0.5 m) arranged in pairs. In each pair, Anthriscus individuals were removed from one plot, the other paired plot acting as control. We periodically recorded the presence and abundance of the remanent species of herbs inside the plots, and then we characterized the species diversity and evenness over time (Shannon's index, H′ and Pielou's index, J′). Finally, in a second experiment we measured experimentally the presence or absence of Anthriscus against the survival of four native herb species (Bowlesia incana, Bromus berteroanus, Pectocarya linearis, and Moscharia pinnatifida). Here we used 20 0.5 × 0.5 m plots where we randomly transplanted seedlings of native herbs and Arnthiscus. Then, for each species and plot we determined their survival (%) according to the number of seedlings initially transplanted. The samplings show strong association between the presence of Anthriscus on edge habitat in the matorral. The maximum densities were noted in these microhabitat types whereas in open areas and under-fragment sites Anthriscus shows very low or null densities. At the end of the first trials, the plots with Anthriscus showed a Shannon diversity index H′ = 0. 41 (±0. 11 SE), while in plots without Anthriscus this value was 1. 19 (±0. 1 SE), both as averages. Pielou's evenness index (J′) yielded values of 0. 23 (±0.06 SE) and 0.59 (±0.04 SE) for treatments with and without Anthriscus, respectively. Similarly, the second trials shows that the survival of the four native herbs was drastically decreased in the presence of Anthriscus: by 64% for Bowlesiaincana, 43% for Bromusberteroanus, 46% for Moscharia pinnatifida, and 76% for Pectocarialinearis. Our study shows that the effects of Anthriscus include an inhibition of the establishment of native plants and a decrease in their survival in edge habitats, therefore affecting the composition and diversity of the local herb layer. Thus, Anthriscus is invading a refuge habitat for native herbs in the Chilean matorral, decreasing the native herb diversity and survival. © Springer Science+Business Media B.V. 2009.

Sartor C.E.,CONICET | Marone L.,CONICET | Marone L.,Center for Advanced Studies in Ecology and Biodiversity | Marone L.,National University of Cuyo
Journal of Arid Environments | Year: 2010

Annual forbs form short-term persistent soil seed banks whereas perennial grasses form mostly transient ones in the central Monte desert. A conceptual framework predicts that annual forb seeds will have primary dormancy, whereas perennial grasses will have low dormancy levels. We assessed whether the dormancy traits of four annual forb species and five perennial grass species can account for their soil seed bank dynamics. To overcome dormancy, we treated perennial grasses and autumn annual forbs with high temperatures, and spring annual forbs with low temperatures. To force seeds into secondary dormancy we exposed non-dormant perennial grasses to low temperatures. Most of the annual forbs and two perennial grasses (Setaria leucopila and Sporobolus cryptandrus) showed low germination rates. The remaining perennial grasses presented moderate (Pappophorum caespitosum and Digitaria californica) or high germination levels (Trichloris crinita). Low temperatures increased germination in spring forbs (Chenopodium papulosum and Parthenium hysterophorus), but high temperatures did not break dormancy in autumn forbs (Sphaeralcea miniata and Phacelia artemisioides). Germination of perennial grasses increased after they had been exposed to high temperatures, but only two species reentered into dormancy under low temperature. Given that in the central Monte desert winter-autumn granivores eat mainly grass seeds, we conclude that high seed dormancy and low consumption may contribute to the persistent soil seed bank of most forbs, and that seed dormancy itself does not explain the transience of grass seed banks. © 2009 Elsevier Ltd. All rights reserved.

Loading Center for Advanced Studies in Ecology and Biodiversity collaborators
Loading Center for Advanced Studies in Ecology and Biodiversity collaborators