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351.
Plath M Tobler M Riesch R García de León FJ Giere O Schlupp I 《Die Naturwissenschaften》2007,94(12):991-996
Extreme habitats challenge animals with highly adverse conditions, like extreme temperatures or toxic substances. In this
paper, we report of a fish (Poecilia mexicana) inhabiting a limestone cave in Mexico. Several springs inside the cave are rich in toxic H2S. We demonstrate that a behavioural adaptation, aquatic surface respiration (ASR), allows for the survival of P. mexicana in this extreme, sulphidic habitat. Without the possibility to perform ASR, the survival rate of P. mexicana was low even at comparatively low H2S concentrations. Furthermore, we show that food limitation affects the survival of P. mexicana pointing to energetically costly physiological adaptations to detoxify H2S. 相似文献
352.
Francisco J. Goin Marcelo F. Tejedor Laura Chornogubsky Guillermo M. López Javier N. Gelfo Mariano Bond Michael O. Woodburne Yamila Gurovich Marcelo Reguero 《Die Naturwissenschaften》2012,99(6):449-463
We describe two isolated molariforms recovered from early–middle Eocene (early Lutetian) levels of northwestern Patagonia, Argentina. Comparisons with major lineages of therian and non-therian mammals lead us to refer them to a new genus and species of Gondwanatheria (Allotheria). There is a single root supporting each tooth that is very short, wide, rounded, and covered by cementum; the steep sidewalls, lack of a neck between the crown and root, and the heavily worn stage in both molariforms suggest that they were of a protohypsodont type. Both teeth are strongly worn at their centers, all along their length, with the labial edge less worn than the lingual; they show strong transverse crests that alternate with lingual grooves. The protohypsodont aspect of the teeth, as well as the strong, transverse crests, are suggestive of sudamericid affinities; on the other hand, the thin enamel layer and the occlusal pattern formed by the crests and grooves shows more similarities to molariform teeth of the Ferugliotheriidae. The new taxon adds evidence regarding the (1) extensive radiation of the Gondwanatheria throughout the Southern Hemisphere, (2) persistence of several lineages well after the Cretaceous/Paleogene boundary, and (3) early evolution of hypsodont types among South American herbivorous mammals. 相似文献
353.
Inmaculada de Vicente Victoria Amores Francisco Guerrero Luis Cruz-Pizarro 《Die Naturwissenschaften》2010,97(7):627-635
Electron transport system (ETS) activity of sediments as an indication of microbial metabolic activity was examined in two
adjacent Mediterranean wetlands (southern Spain). We determined the spatio-temporal variation in ETS, and we explored the
potential biological [organic matter (OM), chlorophyll a (Chl a), aerobic and anaerobic bacteria] drivers of sediment ETS
activity. ETS activity was notably higher in the eutrophic Lake Nueva (34.91 μl O2 g−1 D.W. h−1) than in the hypertrophic Lake Honda (24.99 μl O2 g−1 D.W. h−1). Strong spatial differences were observed in ETS in both study sites. Highest ETS values were achieved at the surface sediment
at the deepest sampling station in each lake and a notable reduction in ETS with sediment depth was observed. By using linear
regression and multiple regression analysis, OM was identified as the best predictor of ETS in Lake Honda while Chl a was
the best predictor in Lake Nueva. The strong influence of OM supply on ETS activity in sediment from Lake Honda was the consequence
of the labile nature of sedimentary OM, while a more refractory OM (with a higher contribution of vascular plants) comprised
most of the sedimentary OM from Lake Nueva. By contrast, a large contribution of phytobenthos (supported by a higher lake
water transparency) to ETS has been recognized in sediments from Lake Nueva. In summary, the results of this study revealed
that the relative importance of planktonic primary producers (phytoplankton), benthic algae and vascular plants in the study
sites could explain the differences observed in the intensity of sediment ETS as well as in their drivers. 相似文献
354.
Here, we provide evidence for a wavelength-dependent effect of light on magnetic compass orientation in Pelophylax perezi (order Anura), similar to that observed in Rana catesbeiana (order Anura) and Notophthalmus viridescens (order Urodela), and confirm for the first time in an anuran amphibian that a 90° shift in the direction of magnetic compass
orientation under long-wavelength light (≥500 nm) is due to a direct effect of light on the underlying magnetoreception mechanism.
Although magnetic compass orientation in other animals (e.g., birds and some insects) has been shown to be influenced by the
wavelength and/or intensity of light, these two amphibian orders are the only taxa for which there is direct evidence that
the magnetic compass is light-dependent. The remarkable similarities in the light-dependent magnetic compasses of anurans
and urodeles, which have evolved as separate clades for at least 250 million years, suggest that the light-dependent magnetoreception
mechanism is likely to have evolved in the common ancestor of the Lissamphibia (Early Permian, ~294 million years) and, possibly,
much earlier. Also, we discuss a number of similarities between the functional properties of the light-dependent magnetic
compass in amphibians and blue light-dependent responses to magnetic stimuli in Drosophila melanogaster, which suggest that the wavelength-dependent 90° shift in amphibians may be due to light activation of different redox forms
of a cryptochrome photopigment. Finally, we relate these findings to earlier studies showing that the pineal organ of newts
is the site of the light-dependent magnetic compass and recent neurophysiological evidence showing magnetic field sensitivity
in the frog frontal organ (an outgrowth of the pineal). 相似文献
355.
Rüdiger Riesch Martin Plath Francisco J. García de León Ingo Schlupp 《Die Naturwissenschaften》2010,97(2):133-141
The majority of studies on ecological speciation in animals have investigated the divergence caused by biotic factors like
divergent food sources or predatory regimes. Here, we examined a system where ecological speciation can clearly be ascribed
to abiotic environmental gradients of naturally occurring toxic hydrogen sulfide (H2S). In southern Mexico, two genera of livebearing fishes (Poeciliidae: Poecilia and Gambusia) thrive in various watercourses with different concentrations of H2S. Previous studies have revealed pronounced genetic differentiation between different locally adapted populations in one
species (Poecilia mexicana), pointing towards incipient speciation. In the present study, we examined female reproductive life-history traits in two
species pairs: Gambusia sexradiata (from a nonsulfidic and a sulfidic habitat) and Gambusia eurystoma (sulfide-endemic), as well as P. mexicana (nonsulfidic and sulfidic) and Poecilia sulphuraria (sulfide endemic). We found convergent divergence of life-history traits in response to sulfide; most prominently, extremophile
poeciliids exhibit drastically increased offspring size coupled with reduced fecundity. Furthermore, within each genus, this
trend increased with increasing sulfide concentrations and was most pronounced in the two endemic sulfur-adapted species.
We discuss the adaptive significance of large offspring size in toxic environments and propose that divergent life-history
evolution may promote further ecological divergence through isolation by adaptation. 相似文献
356.
Laura Benegas Francisco Jiménez Bruno Locatelli Jorge Faustino Max Campos 《Mitigation and Adaptation Strategies for Global Change》2009,14(2):169-183
The current study shows the process and the results of a methodology proposed to contribute with the issue of how to evaluate
the adaptation to climate variability and future climate change. The proposed methodology consists of a standard to evaluate
farmer’s adaptation to climate variability, mainly due to drought in watersheds in Central America; and was created with contributions
from experts and professionals around this region. The phases for this process were: (1) literature review about the topic,
(2) development of a preliminary standard, (3) expert interviews for the evaluation of this preliminary standard, (4) construction
of a standard to evaluate the issue of adaptation to climate variability emphasizing drought through contributions from experts
and their preliminary evaluations, (5) applicability test of this standard for the evaluation of climate variability under
real conditions and (6) application of this standard through a case study in the Aguas Calientes river sub-watershed in Nicaragua,
which permanently undergoes drought problems and climate variability. This standard has five main principles that go from
the general, considering regional and national policies and institutionalism, to the specifics at the level of watersheds.
In addition to those principles, the standard contains ten criteria, 26 indicators and 51 verifiers distributed among the
main five principles. In the process for testing this standard in the Aguas Calientes river watershed in Nicaragua, the score
for the general applicability to this standard was middle-level (score of 3 in a scale of 1 to 5), although, for the main
principles of this standard, the score was four (high). 相似文献
357.
Francisco Escobedo Sebastian Varela Min Zhao John E. Wagner Wayne Zipperer 《Environmental Science & Policy》2010,13(5):362-372
Urban forest management and policies have been promoted as a tool to mitigate carbon dioxide (CO2) emissions. This study used existing CO2 reduction measures from subtropical Miami-Dade and Gainesville, USA and modeled carbon storage and sequestration by trees to analyze policies that use urban forests to offset carbon emissions. Field data were analyzed, modeled, and spatially analyzed to compare CO2 sequestered by managing urban forests to equivalent amounts of CO2 emitted in both urban areas. Urban forests in Gainesville have greater tree density, store more carbon and present lower per-tree sequestration rates than Miami-Dade as a result of environmental conditions and urbanization patterns. Areas characterized by natural pine-oak forests, mangroves, and stands of highly invasive trees were most apt at sequestering CO2. Results indicate that urban tree sequestration offsets CO2 emissions and, relative to total city-wide emissions, is moderately effective at 3.4 percent and 1.8 percent in Gainesville and Miami-Dade, respectively. Moreover, converting available non-treed areas into urban forests would not increase overall CO2 emission reductions substantially. Current CO2 sequestration by trees was comparable to implemented CO2 reduction policies. However, long-term objectives, multiple ecosystem services, costs, community needs, and preservation of existing forests should be considered when managing trees for climate change mitigation and other ecosystem services. 相似文献
358.
Using and comparing two nonparametric methods (CART and MARS) to model the potential distribution of gullies 总被引:1,自引:0,他引:1
Gully erosion represents an important soil degradation process in rangelands. In order to take preventive or control measures and to reduce its environmental damages and economical costs it is useful to localize the points in the landscape where gullying takes place and to determine the importance of the different factors involved. The study is carried out in Extremadura, southwest Spain. The main objectives of this work are: (a) comparing two nonparametric schemes to model the potential distribution of gullies, (b) evaluating the importance of the different factors involved in gullying processes, (c) analyzing the role of prevalence in the success of the model and finally, (d) implementing and mapping the results with the help of a Geographical Information System (GIS). Two methods were used to model the response of a dependent variable (gullying) from a set of independent variables: Classification And Regression Trees (CART) and Multivariate Adaptive Regression Splines (MARS). Three different datasets were used; the first one for constructing the model (training dataset) and the others for validating the model (external datasets). These datasets are formed by a target variable (presence or absence of gullies) and a set of independent variables. The dependent variable was obtained by mapping the locations of gullies with the help of a GPS and high resolution aerial ortophotographs. A set of 32 independent variables reflecting topography, lithology, soil type, climate, land use and vegetation cover of each area were used. The performance of the models was evaluated using a non-dependent threshold method: the Receiver Operating Characteristic (ROC) curve. The results showed a better performance of MARS for predicting gullying with areas under the ROC curve of 0.98 and 0.97 for the validation datasets, while CART presented values of 0.96 and 0.66. 相似文献
359.
A global evaluation of metabolic theory as an explanation for terrestrial species richness gradients 总被引:5,自引:0,他引:5
Hawkins BA Albuquerque FS Araujo MB Beck J Bini LM Cabrero-Sañudo FJ Castro-Parga I Diniz-Filho JA Ferrer-Castan D Field R Gómez JF Hortal J Kerr JT Kitching IJ León-Cortés JL Lobo JM Montoya D Moreno JC Olalla-Tárraga MA Pausas JG Qian H Rahbek C Rodríguez MA Sanders NJ Williams P 《Ecology》2007,88(8):1877-1888
We compiled 46 broadscale data sets of species richness for a wide range of terrestrial plant, invertebrate, and ectothermic vertebrate groups in all parts of the world to test the ability of metabolic theory to account for observed diversity gradients. The theory makes two related predictions: (1) In-transformed richness is linearly associated with a linear, inverse transformation of annual temperature, and (2) the slope of the relationship is near -0.65. Of the 46 data sets, 14 had no significant relationship; of the remaining 32, nine were linear, meeting prediction 1. Model I (ordinary least squares, OLS) and model II (reduced major axis, RMA) regressions then tested the linear slopes against prediction 2. In the 23 data sets having nonlinear relationships between richness and temperature, split-line regression divided the data into linear components, and regressions were done on each component to test prediction 2 for subsets of the data. Of the 46 data sets analyzed in their entirety using OLS regression, one was consistent with metabolic theory (meeting both predictions), and one was possibly consistent. Using RMA regression, no data sets were consistent. Of 67 analyses of prediction 2 using OLS regression on all linear data sets and subsets, two were consistent with the prediction, and four were possibly consistent. Using RMA regression, one was consistent (albeit weakly), and four were possibly consistent. We also found that the relationship between richness and temperature is both taxonomically and geographically conditional, and there is no evidence for a universal response of diversity to temperature. Meta-analyses confirmed significant heterogeneity in slopes among data sets, and the combined slopes across studies were significantly lower than the range of slopes predicted by metabolic theory based on both OLS and RMA regressions. We conclude that metabolic theory, as currently formulated, is a poor predictor of observed diversity gradients in most terrestrial systems. 相似文献
360.
Carla da Silva Carneiro Eliane Teixeira Mársico Edgar Francisco Oliveira de Jesus Roberta de Oliveira Resende Ribeiro Renata de Faria Barbosa 《Chemistry and Ecology》2013,29(1):1-8
Trace elements were determined in fish and oysters from Sepetiba Bay, Brazil, by total reflection Xray fluorescence using synchrotron radiation (SRTXRF). Cr, Mn, Fe, Ni, Cu, Zn and Se were determined in fish muscles and organs and in oyster soft tissue. SRTXRF was shown to be a good tool for the analysis of trace elements from biological tissue samples. Overall, the levels of the analysed metals were higher in oysters than in the fish samples. Metals were not uniformly distributed throughout the body of the analysed fish. The detected concentrations of Cr, Zn and Se were very high in some samples, surpassing the maximum limits established by Brazilian legislation. 相似文献