Scielo RSS <![CDATA[Revista chilena de historia natural]]> vol. 89 num. lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Influence of bamboo dieback on arboreal diversity in a subtropical forest fragment</b>]]> BACKGROUND: The vegetation structure and dynamics in subtropical forest fragments is influenced by the bamboo density. After the reproductive events followed by the death of the bamboos, is critical to understanding community structure and regeneration processes over time. The aim of this study was to evaluate temporally the influence of height and density of Merostachys multiramea on the richness, density and diversity of tree species after the event of bamboo dieback. The study was conducted in subtropical forest in southern Brazil, characterized by intense fragmentation of habitats, which facilitates the establishment of bamboo species RESULTS: We observed an increase in bamboo height over time, as well as an increase in the number of individuals between the fourth and sixth years of study. The number of M. multiramea individuals did not influence the density of regenerated individuals, but residuals analysis for estimated species richness showed the influence of bamboo on regeneration process. Six year after the bamboos death we observed a higher similarity in density of individuals between the sampling units CONCLUSIONS: The results of this study demonstrated distinct phytosociological structures during the different years of study, indicating that six years after the bamboos death, the vegetation structure has a higher similarity in the evaluated forest fragments in Southern Brazil, indicating a possible stabilization in the forest structure. <![CDATA[<b>Expression pattern of heat shock proteins during acute thermal stress in the Antarctic sea urchin, <i>Sterechinus neumayeri</i></b>]]> BACKGROUND: Antarctic marine organisms have evolved a variety of physiological, life-history and molecular adaptations that allow them to cope with the extreme conditions in one of the coldest and most temperature-stable marine environments on Earth. The increase in temperature of the Southern Ocean, product of climate change, represents a great challenge for the survival of these organisms. It has been documented that some Antarctic marine invertebrates are not capable of generating a thermal stress response by means of an increase in the synthesis of heat shock proteins, which could be related with their low capacity for acclimatization. In order to understand the role of heat shock proteins as a compensatory response in Antarctic marine species to projected scenarios of increased seawater temperatures, we assessed the expression of the genes Hsp90, Grp78, Hyou1 and Hsc70 in the Antarctic sea urchin Sterechinus neumayeri under three thermal treatments (1 °C, 3 °C and 5 °C), for a period of exposure of 1, 24 and 48 h RESULTS: The results obtained showed that these genes were expressed themselves in all of the tissues analyzed in a constitutive form. During acute thermal stress, an overexpression of the Hsp90, Grp78 and Hyou1 genes was observed in coelomocyte samples at 3 °C after 48 h, while in esophageal samples, an increase in Hsp90 and Grp78 expression was observed after 48 h. Thermal stress at 5 °C, in general, did not produce a significant increase in the expression of the genes that were studied. The expression of Hsp70 did not show modifications in its expression as a result of thermal stress CONCLUSIONS: S. neumayeri is capable of overexpressing stress proteins as a result of thermal stress, however, this response is delayed and to a lesser degree compared to other Antarctic or temperate species. These results indicate that adult individuals could cope with the expected impacts caused by an increase in coastal sea temperatures in the Southern Ocean. <![CDATA[<b>Independent effects of grazing and tide pool habitats on the early colonisation of an intertidal community on western Antarctic Peninsula</b>]]> BACKGROUND: Prevailing environmental conditions can modulate the structuring role of biotic interactions. In intertidal habitats, less stressful environmental conditions and/or higher grazer densities may allow grazing effects to be stronger in tide pools than on emergent rocks. To test this hypothesis, we conducted a manipulative experiment on an intertidal rocky shore in Fildes Bay, King George Island, in which the effect of the dominant grazer Nacella polaris on the structure of benthic periphyton communities was compared between emergent rock and tide pool habitats. Also, we determined the spatial variation in density, weight, and maximum length of individuals of N. polaris in both habitats RESULTS: The density of N. polaris was significantly larger in tide pools than on emergent rocks. Contrarily, we observed no significant differences in morphological parameters of N. polaris between both habitats or between intertidal elevations. In the manipulative study, we observed a greater taxonomic richness, diversity, and abundance of periphyton on emergent rocks than in tide pools. These variables also showed, in comparison with control areas, significantly higher values in experimental areas where herbivores were excluded by means of stainless-steel fences. The effects of habitat and grazer exclusion treatments were independent of each other, as no statistically significant interaction between both factors was observed CONCLUSIONS: Our results showed significant, but independent, effects of tide pool habitats and grazing on the early colonisation of these assemblages. Albeit the grazing effects of other herbivores such as amphipods and small gastropods cannot be ruled out, we suggest that traits of N. polaris, such as high mobility and circadian activity, allow this species to exert a firm control on the intertidal Antarctic assemblages across local environmental conditions. <![CDATA[<b>Pollen record of disturbed topsoil as an indirect measurement of the potential risk of the introduction of non-native plants in maritime Antarctica</b>]]> BACKGROUND: This is a study of current pollen rain on soil disturbed by human use on the Fildes Peninsula, King George Island, South Shetland Islands. A sector strongly affected by human activity, an area between the Eduardo Frei Montalva Chilean Air Force (FACH) base and the Professor Julio Escudero base of the Chilean Antarctic Institute (INACH) were sampled. A less used sector associated with scientific activity and controlled tourism, Ardley Island, and an area of low human activity, the terminal moraine of the Collins glacier, were also sampled. The samples were collected in the southern summer of 2015 and kept in the Palynology and Plant Ecology Laboratory of the Los Angeles Campus of the Universidad de Concepción, Chile FINDINGS: The area of greatest human activity concentrated the greatest diversity (12 taxa) of pollen grains. Three taxa are considered native to the region. Non-native taxa determined for this sector in turn had the greatest invasion (INV) factor. The dominant families were Brassicaceae and Asteraceae. The results for Ardley and Collins represent the cryptogamic flora and grasses typical of the ecosystem CONCLUSION: Under the current climate change scenario, the pollen rain in Antarctic soil, in addition to obeying the random patterns of its natural dispersion, could be interpreted as an indirect measurement of the potential risk of the passive transport of propagules to Antarctica mediated by human beings.<hr/>La presente investigación es un estudio de la lluvia de polen actual en suelo perturbado por uso antrópico en la Península Fildes, Isla Rey Jorge, Islas Shetland del Sur. Se muestreó un sector fuertemente afectado por actividad humana en un área comprendida entre la base de la Fuerza Aérea de Chile (FACH) Eduardo Frei Montalva y la base del Instituto Antártico Chileno (INACH) Profesor Julio Escudero. Un sector con menos presión de uso, Isla Ardley, asociado con actividad científica y turismo controlado también fue estudiado. Finalmente, un tercer sector fue analizado, correspondiente a la morrena terminal del glaciar Collins, que presenta muy baja actividad humana. Las muestras fueron colectadas en el verano de 2015 y analizadas en el Laboratorio de Palinología y Ecología Vegetal del Campus Los Ángeles de la Universidad de Concepción, Chile. El área que presenta la mayor concentración de actividad humana concentró la mayor diversidad de granos de polen (12 taxa). Tres taxa son considerados nativos para la región. Los taxa no nativos determinados para el sector presentaron a su vez, el mayor factor de invasión (INV). Las familias dominantes fueron Brassicaceae y Asteraceae. Los resultados para los sectores de Isla Ardley y glaciar Collins representaron la flora criptogámica y de pastos típicos del ecosistema. Bajo el presente escenario de cambio climático, la lluvia de polen determinada en suelo antártico podría estar reflejando además de la azarosidad propia de la dispersión natural una medida indirecta del riesgo potencial de un transporte pasivo de propágulos a Antártica mediado por el hombre. <![CDATA[<b>Stress tolerance of Antarctic macroalgae in the early life stages</b>]]> BACKGROUND: Early life stages of macroalgae, especially from polar species, can be highly vulnerable to physical stressors, leading to important consequences for the fate of the whole population in scenarios of changing environmental variability. In the present study, tolerance to UV and temperature stress, as measured by rapid adjustment of photochemistry, Fv/Fm, and photosynthetic characteristics based on P-E curves (ETRmax, α and Ek), was assessed in the early life stages of six Antarctic macroalgal species from eulittoral (Pyropia endiviifolia, Iridaea cordata, Adenocystis utricularis and Monostroma hariotii) and sublittoral (Ascoseira mirabilis and Gigartina skottsbergii. RESULTS: Reproductive cells of eulittoral species showed the highest light demands (Ek &gt;45 μmol photon m-2 s-1) when compared to those from sublittoral species (Ek<30 μmol photon m-2 s-1). Short-term experiments of 1 h revealed that reproductive cells of P. endiviifolia, A. utricularis and M. hariotii had the highest temperature tolerance with a decrease of Fv/Fm observed only at 30 °C, while carpospores of G. skottsbergii exhibited the highest sensitivity to temperature increase with a decrease of Fv/Fm, which could be observed at 5 °C. UV tolerance was observed in reproductive cells of the eulittoral species with < 20 % inhibition in Fv/Fm from UV after four hours of exposure, while sublittoral species were more sensitive with &gt;30 % inhibition in Fv/Fm in the same condition. Enhanced temperature (7 and 12 °C) improved the tolerance of I. cordata compared to 2 °C, but exacerbated the detrimental effects of UV on A. mirabilis. CONCLUSION: Results showed that photosynthetic characteristics varied among reproductive cells of different species, reflecting the vertical zonation of parental thalli. Otherwise, these differences appear to underlie biogeographical and evolutionary components. In addition, UV tolerance was modulated by temperature increase, while temperature increase, in turn, ameliorated the detrimental effects of stress treatments in some eulittoral species (I. cordata tetraspores). In sublittoral A. mirabilis gametangia, temperature exacerbated the reduction of photosynthetic efficiency. <![CDATA[<b>Photosynthetic UV stress tolerance of the Antarctic snow alga <i>Chlorella </i>sp. modified by enhanced temperature?</b>]]> BACKGROUND: Photosynthetic characteristics and the effect of UV radiation and elevated temperature measured were studied in Chlorella sp. isolated from a snow microalgal community at King George Island, Maritime Antarctica through the chlorophyll florescence (rapid light curves and maximum quantum yield, respectively). The environmental context was monitored through measurements of spectral depth profiles of solar radiation (down to 40 cm) in the snowpack as well as a through continuous recording of temperature and PAR using dataloggers located at different depths (0-30 cm) within the snow column RESULTS: The photochemistry of Chlorella sp. was affected by UV radiation in a 12-h laboratory exposure under all studied temperatures (5, 10, 15, 20 °C): the algae exposed to PAR + UV-A radiation were inhibited by 5.8 % whilst PAR + UV-A + UV-B radiation decreased Fv/Fm by 15.8 %. In both treatments the 12-h recovery after UV exposure was almost complete (80-100 %). Electron transport based P-I curve parameters maximal electron transport rate (ETRmax), photosynthetic efficiency (α) and the saturating irradiance (Ek) no varied in response to different temperatures CONCLUSIONS: Results revealed that Chlorella sp. not only shows high photosynthetic efficiency at ambient conditions, but also exhibits tolerance to solar radiation under higher temperatures and possessing a capacity for recovery after inhibition of photosynthesis by UV radiation <![CDATA[<b>Successional patterns along soil development gradients formed by glacier retreat in the Maritime Antarctic, King George Island</b>]]> BACKGROUND: Maritime Antarctica is severely affected by climate change and accelerating glacier retreat forming temporal gradients of soil development. Successional patterns of soil development and plant succession in the region are largely unknown, as are the feedback mechanisms between both processes. Here we identify three temporal gradients representing horizontal and vertical glacier retreat, as well as formation of raised beaches due to isostatic uplift, and describe soil formation and plant succession along them. Our hypotheses are (i) plants in Antarctica are able to modulate the two base parameters in soil development, organic C content and pH, along the temporal gradients, leading to an increase in organic carbon and soil acidity at relatively short time scales, (ii) the soil development induces succession along these gradients, and (iii) with increasing soil development, bryophytes and Deschampsia antarctica develop mycorrhiza in maritime Antarctica in order to foster interaction with soil RESULTS: All temporal gradients showed soil development leading to differentiation of soil horizons, carbon accumulation and increasing pH with age. Photoautptroph succession occurred rapidly after glacier retreat, but occurrences of mosses and lichens interacting with soils by rhizoids or rhizines were only observed in the later stages. The community of ground dwelling mosses and lichens is the climax community of soil succession, as the Antarctic hairgrass D. antarctica was restricted to ornithic soils. Neither D. antarctica nor mosses at the best developed soils showed any sign of mycorrhization CONCLUSION: Temporal gradients formed by glacier retreat can be identified in maritime Antarctic, where soil development and plant succession of a remarkable pace can be observed, although pseudo-succession occurs by fertilization gradients caused by bird feces. Thus, the majority of ice-free surface in Antarctica is colonized by plant communities which interact with soil by litter input rather than by direct transfer of photoassimilates to soil <![CDATA[<b>Occurrence of toxic blooms of <i>Microcystis aeruginosa </i>in a central Chilean (36° Lat. S) urban lake</b>]]> BACKGROUND: During the last decades the frequency and global distribution of toxic cyanobacteria blooms has increased globally, which has been attributed to the eutrophication and climate change. In Chile there have been reports on blooms in aquatic ecosystem in localities with high density population and on the presence of five congeners of microcystins but only two documented toxics blooms with hundreds fish kills. We investigated the presence of toxic cyanobacteria blooms in the Lo Galindo urban lake, Concepción city, and the environmental factors that influence the abundance of cyanobacteria and microcystins concentration. Lo Galindo Lake, is used for various recreational and eventually as a drinking water source RESULTS: Toxic blooms of Microcystis aeruginosa are developed in Lo Galindo lake, those that occur throughout the year in a wide range of environmental conditions, forming scums blooms during summer and dispersive blooms in all seasons. There are different microcystin congeners, the most frequent congener was MC-RR (21 %) and the highest concentration corresponded to 115.4 μg L-1 MC-LR CONCLUSIONS: The dominance and development of the M. aeruginosa blooms in the lake is determined by various environmental factors such as temperature, nutrients, diversity of taxa and wind speed that affect the formation of disperse-type blooms and/or scums; the latter are developed only in summer, coinciding with the highest temperature and concentrations of total microcystins. In the lake the microcystin and different types of congener is highly variable, so special care is recommended to use lake water for consumption and for recreational activities. The emergence and persistence of Microcystis blooms in this body of water are considered a potential health risk for the inhabitants of the area, considering the proximity and the system use by the inhabitants<hr/>ANTECEDENTES: Durante las últimas décadas la frecuencia y la distribución global de las floraciones de cianobacterias tóxicas han aumentado a nivel mundial, lo que ha sido atribuido a la eutrofización y al cambio climático global. En Chile existen reportes de floraciones en ecosistemas acuáticos en zonas con alta densidad poblacional y la presencia de cinco congéneres de microcistinas, pero sólo dos floraciones tóxicas que ocasionaron la muerte de cientos de peces. Se investigó la presencia de floraciones de cianobacterias tóxicas en el lago urbano Lo Galindo, ciudad de Concepción, y los factores ambientales que influyen en la abundancia de cianobacterias y concentración de microcistina. Este lago, se utiliza para recreación y como fuente de agua potable alternativa para la ciudad RESULTADOS: En el lago se desarrollan floraciones tóxicas de Microcystis aeruginosa, las que se presentan durante todo el año en un amplio rango de condiciones ambientales, formando floraciones tipo acumulativas (scums) durante el verano y dispersivas en todas las épocas del año. Existen diferentes congéneres de microcistina, el más frecuente es MC-RR (21.0 %) y el de mayor concentración MC-LR (115.4 μg L-1 CONCLUSIÓN: La dominancia y el desarrollo de las floraciones de M. aeruginosa está determinada por diversos factores ambientales como la temperatura, nutrientes, diversidad de taxa y la velocidad del viento que afectan a la formación de floraciones dispersivas y/o scums, esta última se desarrolla sólo en verano, coincidiendo con las mayores temperaturas y concentraciones de microcistinas totales. La concentración de los congéneres es altamente variable en el lago, por lo que se recomienda especial cuidado en usar el agua para consumo y para actividades recreativas. La aparición y persistencia de las proliferaciones de M. aeruginosa en este cuerpo de agua se consideran un riesgo potencial para la salud de los habitantes de la zona, teniendo en cuenta la proximidad y el uso del sistema por los habitantes <![CDATA[<b>Rare, Endangered and Threatened (RET) climbers of Southern Western Ghats, India</b>]]> BACKGROUND AND AIMS: The Mountains of the Western Ghats are the second most important shelter in the world for threatened species. The current paper is an attempt to study the conservation assessment of rare, endangered and threatened species (RET) of the southern Western Ghats. A species is endangered when it is threatened with extinction. Since time began, countless species have gone extinct from natural processes. The present study was conducted to identify the rare, endangered and threatened climbing plants in Southern Western Ghats of Tamil Nadu, India. METHODS: The plant collection and identification of the RET listed climbing species of the Southern Western Ghats was done during 2011-2014. The collection and identified RET plant species from the study were selected from different hills (forest) of Tamil Nadu. During the work the selected study sites were visited, plant specimens were collected and systematically pressed, stored for identification KEY RESULTS: A total number of 285 climber species comprising 125 genera of 41 families were identified from Southern Western Ghats of Tamil Nadu. Out of 285, 33 species are listed as RET species like Ceropegia mannarana Umam. & Daniel and Gloriosa superba L. fond to be Endangered species and Celastrus paniculata Willd., Aganosma cymosa G.Don. Smilax wightii A. DC., Corallocarpus gracilipes Cong., are rare species. The most specious families include Asclepiadaceae (7 species), Convolvulaceae (5-species) followed by, Fabaceae (4-species), Cucurbitaceae and Liliaceae each 3-species, and all the other remaining families having two or one species each CONCLUSION: Some of the threatened factors such as over-exploitation of natural resources and other anthropogenic activities adversely affect the existing ecosystem and it may lead to the rarity of many species in future. There is an urgent need for developing pragmatic conservation strategies for endemic plants in the southern Western Ghats, which may lead to their effective protection