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1.
Altitudinal distribution limits of aquatic macroinvertebrates: an experimental test in a tropical alpine stream 下载免费PDF全文
PHILIP B. MADSEN ANDRÉS MORABOWEN PATRICIO ANDINO RODRIGO ESPINOSA SOPHIE CAUVY‐FRAUNIÉ OLIVIER DANGLES DEAN JACOBSEN 《Ecological Entomology》2015,40(5):629-638
1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. 2. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (Plecoptera), Scirtes (Coleoptera) and Anomalocosmoecus (Trichoptera), and the amphipod Hyalella in an Ecuadorian glacier‐fed stream (4100–4500 m a.s.l.). The following were performed: (i) quantitative benthic sampling at three sites to determine altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short‐term (14 days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5 °C vs. 10 °C) and oxygen saturation (55% vs. 62%). 3. The transplant experiment reduced survival to a varying degree among taxa, but Claudioperla survived well at a site where it did not naturally occur. In the in situ experiment, Scirtes and Hyalella decreased their activity at lower oxygen saturation, whereas Andesiops and Anomalocosmoecus did so at a low temperature. The decrease in activity from a high to a low temperature and oxygen for the five taxa was significantly correlated with their mortality in the transplant experiment. 4. Together the present experiments indicate that even relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits. 相似文献
2.
Thermal tolerance and recovery behaviour of Thorectes lusitanicus (Coleoptera,Geotrupidae) 下载免费PDF全文
BELÉN GALLEGO JOSÉ R. VERDÚ LUIS M. CARRASCAL JORGE M. LOBO 《Ecological Entomology》2017,42(6):758-767
1. Population differences in physiological responses are examined in Thorectes lusitanicus, an endemic Iberian dung beetle species, by submitting individuals of different populations to the same experimental and acclimation conditions. 2. An infrared thermography protocol was used, consisting of three assays: start of activity, cold response, and heat response. Individuals of 12 populations were studied and the comparative explanatory capacities of several environmental factors in relation to the observed inter‐population differences were examined. 3. The heating rate from chill coma to the beginning of activity was the variable with the highest discrimination power among the studied populations, accounting for 94% of the observed variance. Regarding the heat response, only six of the 16 thermal variables reached significance (inter‐population differences accounted for 52–74% in these six thermal parameters). 4. From the three considered environmental factors (Mediterranean climate, land cover, and trophic characteristics) only land cover characteristics remain statistically significant, affecting the cold response of individuals. 5. Thorectes lusitanicus is a species characterised by a high diversity of thermotolerance and recovery traits across populations with a low degree of association with broad environmental factors. Finally, it is suggested that the apterous character of this species could be a determinant factor explaining the high diversity of ecophysiological traits related to thermal stress tolerance and the recovery time. 相似文献
3.
Field-measured grazing rates (ml/animal/d) of cladocerans (mostly daphniids) and diaptomids were assembled from various published
studies and plotted as a function of corresponding phytoplankton concentration (μg l−1 f.w.). Filtering rates of both zooplankton groups initially increased with seston concentration until maximal grazing rates
were observed at approximately 4 × 102 and 1 × 102 μg l−1 for cladocerans and copepods, respectively; at higher algal concentrations, filtering rates of both declined as a function
of food concentration. The shape of these curves are most consistent with Holling's (1966) Type 3 functional response.
We found little support for the Type 3 functional response in published laboratory studies of Daphnia; most investigators report either a Type 1 or Type 2 response. The one study in which the Type 3 response was observed involved
experiments where animals were acclimated at low food concentrations for 24 h, whereas those studies associated with response
Types 1 or 2 had acclimation periods of only 1 to 3 h. We therefore assembled relevant data from the literature to examine
the effect of acclimation period on the feeding rates of Daphnia at low food concentrations. In the absence of any acclimation, animals filtered at extremely low rates. After 2 h of acclimation,
however, filtering rates increased 4 to 5-fold but declined again with longer durations; after > 70 h of pre-conditioning,
filtering rates were almost as low as they had been with no acclimation.
We also found little support for the Type 3 functional response in published studies of copepods. The only study associated
with a Type 3 response involved a marine copepod that had been subjected to a starvation period of 48 h; however, an analysis
of the effects of acclimation period did not yield conclusive evidence that filtering rates of freshwater copepods (Diaptomus and Eudiaptomus) decrease significantly with acclimation duration.
The low filtering rates associated with long acclimation periods in laboratory experiments appears to be a direct result of
animals becoming emaciated from prolonged exposure to low food concentrations, a situation which renders them incapable of
high filtering rates. This may explain the Type 3 functional response for field cladocerans, since zooplankton in food-limiting
situations are constantly exposed to low food concentrations, and would therefore have low body carbon and consequently less
energy to filter-feed. We cannot, however, use this to explain the Type 3 response for field diaptomids, since copepods in
the laboratory did not appear to lose body carbon even after 72 h of feeding at very low food levels, and there was inconclusive
evidence that either Diaptomus or Eudiaptomus decrease their filtering rates with acclimation period.
Although Incipient Limiting Concentrations (ILC) for Daphnia ranged from 1 to 8.5 × 103 μg 1−1, more than half of these fell between 1 and 3 × 103 μg l−1, bracketing the value of 2.7 × 102 μg l−1 for field cladocerans. There was, however, a great deal of variation in reported maximum ingestion rates (MIR), maximum filtering
rates (MFR) and ILC values for Daphnia magna. ILC values from the few laboratory studies of freshwater copepods ranged between 0.5 to 2.8 × 103 μg 1−1, and was higher than the ILC value of approximately 0.2 × 103 μg l−1 calculated for field populations of D. minutus. Generally, there was considerable agreement among laboratory studies regarding the shape of grazing-rate and ingestion-rate
curves when data were converted to similar units and presented on standardized scales. 相似文献
4.
5.
ENRIQUE JHONATAN ROMO-MARTÍNEZ GABRIELA MARTÍNEZ-CORTÉS REYNA LUCÍA BARAJAS-TORRES RODRIGO RUBI-CASTELLANOS MARÍA TERESA MAGAÑA-TORRES HÉCTOR RANGEL-VILLALOBOS JUAN RAMÓN GONZÁLEZ-GARCÍA 《Journal of genetics》2012,91(3):297-302
Morphological variation of the Y chromosome has been observed in different populations. This variation is mostly related to the heteromorphic Yq12 band, which is composed of a variable block of constitutive heterochromatin. The Yqh+ heteromorphism has a worldwide frequency of 2.85% and is considered clinically innocuous. The aim of this study was to identify the ancestry of the Yqh+ heteromorphism present in individuals from western Mexico. For this purpose, 17 Y-chromosome single nucleotide polymorphisms were analysed by multiplex polymerase chain reaction and SNaPshot assays. In 28 Yqh+ males, only five haplogroups were observed; with a haplogroup diversity of 0.4841 ± 0.1094, which was less than that observed in a study of unselected Mexican mestizo population. Differences were specifically conferred by the high frequencies of haplogroups R1b1 and P*(xQ,R), and by the absence of the Amerindian haplogroup Q (Q*(xQ1a3a) plus Q1a3a) from the Yqh+ group. This study suggests a post-1492 incorporation for Yqh+ chromosomes into the Mexican northwestern population. 相似文献
6.
Accumulation of the labdane diterpene Marrubiin in glandular trichome cells along the ontogeny of Marrubium vulgare plants 总被引:1,自引:0,他引:1
The content of the diterpene Marrubiin was assessed by GC-FID in leaves of Marrubium vulgare plants along their ontogeny. Maximum accumulation occurred just before flowering time and in fully expanded leaves. After
feeding the plants with radio labeled [3H]-geranyl geranyl diphosphate, up to 70% of the radioactivity was recovered in HPLC-Rt coincidental with authentic Marrubiin,
which was also characterized by GC-EIMS, thus confirming that the biosynthesis of Marrubiin proceeds through the 1-deoxy-D-xylulose-5-phosphate
pathway. The major accumulation of radioactivity occurred in glandular trichome cells, and the product remained stable throughout. 相似文献
7.
Brenda Díaz‐Crdenas Eduardo Ruiz‐Sanchez Hctor Gadsden Jos Manuel García‐Enriquez Patricia Castro‐Felix Gamaliel Castaeda‐Gaytn Anne Santerre 《Journal of Zoological Systematics and Evolutionary Research》2019,57(4):864-876
The biogeographic history of the Chihuahuan Desert is known to be complex, and there is evidence of the effects of physiographic and climatic events in species diversification and demographic population changes in many taxa. Here, using DNA sequence data, we studied the influence of the physiographic and climatic events that occurred in the Chihuahuan Desert during the Pliocene–Pleistocene transition on the speciation and evolutionary history of the sister lizard species Sceloporus cyanostictus and S. gadsdeni. First, based on mtDNA and nDNA sequences, we estimated the divergence times of the sister species. Then, based on mtDNA sequences, we investigated the demographic history of both species within a phylogeographic framework. The divergence time was inferred to be 1.48 Mya, date that corresponds to the existence of a large lake in the Mapimian subprovince, between the current geographic locations of S. cyanostictus and S. gadsdeni. This lake could have acted as a barrier, leading to the speciation of both species. For the demographic history of the two species, we identified two distinct patterns: the population expansion of S. gadsdeni within the Last Glacial Maximum and the potential population decline of S. cyanostictus. Our results can be used as a guide for the study of other aspects that could be critical to developing conservation actions that ensure the survival of not only S. gadsdeni and S. cyanostictus, but also other co‐occurring lizard species. 相似文献
8.
9.
John F. E. Newman Patricia G. Piatti Martin D. Ryan Fred Brown 《Trends in microbiology》1994,2(12):494-498
Foot-and-mouth disease virus and poliovirus each contain several minor polypeptides, in addition to the four structural proteins. One of these, the viral RNA polymerase, can also act as a nuclease, hydrolysing the RNA and thus destroying viral infectivity. It is tightly bound to the RNA and may be the packaging signal for assembly of the particle. 相似文献
10.
Graciela E. Santillán Marisa J. Sandoval Yuti Chernajovsky Patricia L. Orchansky 《Molecular and cellular biochemistry》1992,110(2):181-191
A number of cell-surface proteins are anchored in plasma membranes by a glycosylated phosphatidylinositol (PI) moiety that
is covalently attached to the carboxyl-terminal amino acid of the mature protein. We have previously reported the construction
of a cDNA clone of a truncated Platelet-derived growth factor (PDGF) receptor that consists of the extracellular domain without
the transmembrane and cytoplasmic domains. In the construction of the vector, a sequence of 51 base pairs (bp) from the 3′-untranslated
region of the receptor cDNA was linked in frame with the external domain coding sequence. The truncated receptor protein with
the peptide VTSGHCHEERVDRHDGE fused to its carboxyl terminus was covalently attached to the membrane by a PI linkage and it
was released by phosphatidylinositol specific-phospholipase C (PI-PLC). When the 51 bp sequence was deleted, the external
domain receptor protein was secreted into the media. To determine whether the PI linkage of the protein was due to the 17
amino acids added, the peptide was fused to the carboxyl terminus of the secreted protein human Interferon-β (hu-IFN-β). Chinese
hamster ovary (CHO) cells transfected with the hu-IFN-β cDNA secreted the protein to theconditioned media, whereas CHO cells
transfected with the carboxyl terminus modified-hu-IFN-β cDNA did not secrete detectable levels of protein. CHO cells expressing
the carboxyl terminus modified-hu-IFN-β were treated with PI-PLC, the media and cell lysates were analyzed by SDS-PAGE after
immunoprecipitation with antibodies against hu-IFN-β. The modified protein is anchored to the plasma membrane by a PI linkage
and it is specifically released by PI-PLC, whereas a control preparation of CHO cells expressing wild type hu-IFN-β does not
show the same pattern. The 17 amino acid peptide fused to the carboxyl terminus of IFN-β directs attachment of a PI anchor
and targets the fusion protein to the plasma membrane. 相似文献