The ecoresponsive genome of Daphnia pulex     

Colbourne JK  Pfrender ME  Gilbert D  Thomas WK  Tucker A  Oakley TH  Tokishita S  Aerts A  Arnold GJ  Basu MK  Bauer DJ  Cáceres CE  Carmel L  Casola C  Choi JH  Detter JC  Dong Q  Dusheyko S  Eads BD  Fröhlich T  Geiler-Samerotte KA  Gerlach D  Hatcher P  Jogdeo S  Krijgsveld J  Kriventseva EV  Kültz D  Laforsch C  Lindquist E  Lopez J  Manak JR  Muller J  Pangilinan J  Patwardhan RP  Pitluck S  Pritham EJ  Rechtsteiner A  Rho M  Rogozin IB  Sakarya O  Salamov A  Schaack S  Shapiro H  Shiga Y  Skalitzky C  Smith Z  Souvorov A  Sung W 《Science (New York, N.Y.)》2011,331(6017):555-561

We describe the draft genome of the microcrustacean Daphnia pulex, which is only 200 megabases and contains at least 30,907 genes. The high gene count is a consequence of an elevated rate of gene duplication resulting in tandem gene clusters. More than a third of Daphnia's genes have no detectable homologs in any other available proteome, and the most amplified gene families are specific to the Daphnia lineage. The coexpansion of gene families interacting within metabolic pathways suggests that the maintenance of duplicated genes is not random, and the analysis of gene expression under different environmental conditions reveals that numerous paralogs acquire divergent expression patterns soon after duplication. Daphnia-specific genes, including many additional loci within sequenced regions that are otherwise devoid of annotations, are the most responsive genes to ecological challenges.  相似文献   

Rubidium-87/strontium-87 age of juvinas basaltic achondrite and early igneous activity in the solar system     

Allégre CJ  Birck JL  Fourcade S  Semet MP 《Science (New York, N.Y.)》1975,187(4175):436-438

A (4.60+/-0.07)x10(9) year internal isochron has been drawn for the achondrite Juvinas by the rubidium-87/strontium-87 method. Earlier petrographic investigation of achondrites supplemented by a new ion microprobe study of Juvinas strongly suggest an igneous origin for this class of meteorites. The results thus indicate that igneous activity may have rapidly followed the formation of the achondrites' parent body 4.6x10(9) years ago.  相似文献   

Integrating GIS and homing experiments to study avian movement costs     

A. Desrochers  M. Bélisle  J. Morand-Ferron  J. Bourque 《Landscape Ecology》2011,26(1):47-58

Forest cover reduction may affect movements of forest animals, but resistance to animal movements in and out of forests remains unknown despite its importance for modelling. We tested whether ovenbird (Seiurus aurocapilla), a forest-interior songbird, responds similarly to the amount of forest cover while moving locally (~2 km) and over entire landscapes (~25 km). We compared spatially-explicit simulations to field data to address the issue of resistance to movement in open areas. We caught, banded and translocated 143 territorial males 0.8–27 km away from their territory early in the breeding season. Seventy-eight percent and 50% of translocated males returned (homed) within 10 days following “local” and “landscape” translocations respectively. Independent of translocation distance, homing times increased with decreasing forest in the landscape. With a Geographic Information System (GIS), we simulated “least-cost” paths that homing ovenbirds would ideally take, when resistance to movement in open areas ranged 1–1000 times the resistance to movement in forest. The length, the cumulative cost, and variability of simulated least-cost movement paths increased with increasing resistance in open areas. With landscape translocations, least-cost path length explained homing time better than Euclidean distance, and based on an information-theoretic approach, resistance to movement was estimated to be 27 times greater in open areas than in forests (95% confidence interval: 16–45). However, least-cost path length did not perform better than Euclidean distance with local translocations, and the cumulative cost of least-cost paths was not associated to homing time in either translocation scale. We conclude that resistance to animal movements in open areas can be addressed by a combination of GIS modelling and translocation experiments, and is between one and two orders of magnitude greater than resistance to movements in forests, in the case of ovenbirds.  相似文献   

Edge effect and matrix influence on the nest survival of an old forest specialist,the Brown Creeper (<Emphasis Type="Italic">Certhia americana</Emphasis>)     

Jean-François Poulin  Marc-André Villard 《Landscape Ecology》2011,26(7):911-922

Conservation strategies should be based on a solid understanding of processes underlying species response to landscape change. In forests fragmented by agriculture, elevated nest predation rates have been reported in many forest bird species, especially near edges. In intensively-managed forest landscapes, timber harvesting might also be associated with negative edge effects or broader “context” effects on some species when the matrix provides additional resources to their major nest predators. In this study, we hypothesized that proximity to a forest edge and proportion of cone-producing plantations will increase nest predation risk in fragments of relatively undisturbed forest. We focused on the Brown Creeper (Certhia americana), an indicator species of late-seral forests. We compared habitat configuration and composition at four spatial scales (0.14, 0.5, 1 and 2 km) around 54 nests and related daily nest survival rate to the distance to the nearest forest edge, mean patch size of late-seral forest (r = 141 m), proportion of non-forested lands (r = 141 m), density of maintained roads (r = 1 km), proportion of cone-producing spruce plantations (r = 2 km), and year. The best model included distance to the nearest edge and proportion of cone-producing plantations. Distance of nests to the nearest edge was the best individual predictor of daily nest survival. A larger sample of nests showed a significant threshold in distance to the nearest forest edge; nests located at least 100 m away were more likely to fledge young. These results suggest that even in managed forest landscapes, matrix effects can be important and some bird species may exhibit negative edge effects.  相似文献   

Delineating the drivers of waning wildlife habitat: The predominance of cotton farming on the fringe of protected areas in the Mid-Zambezi Valley, Zimbabwe     

Frédéric Baudron  Marc Corbeels  Jens A. Andersson  Mbulisi Sibanda  Ken E. Giller 《Biological conservation》2011,(5):1481-1493

Zimbabwe’s Mid-Zambezi Valley is of global importance for the emblematic mega-fauna of Africa. Over the past 30 years rapid land use change in this area has substantially reduced wildlife habitat. Tsetse control operations are often blamed for this. In this study, we quantify this change for the Dande Communal Area, Mbire District, of the Mid-Zambezi Valley and analyse the contribution of three major potential drivers: (1) increase in human population; (2) increase in cattle population (and the expansion of associated plough-based agriculture), and; (3) expansion of cotton farming. Although direct effects of land use change on wildlife densities could not be proven, our study suggests that the consequences for elephant and buffalo numbers are negative. All three of the above drivers have contributed to the observed land use change. However, we found farmland to have expanded faster than the human population, and to have followed a similar rate of expansion in cattle sparse, tsetse infested areas as in tsetse free areas where cattle-drawn plough agriculture dominates. This implies the existence of a paramount driver, which we demonstrate to be cotton farming. Contrary to common belief, we argue that tsetse control was not the major trigger behind the dramatic land use change observed, but merely alleviated a constraint to cattle accumulation. We argue that without the presence of a cash crop (cotton), land use change would have been neither as extensive nor as rapid as has been observed. Therefore, conservation agencies should be as concerned by the way people farm as they are by population increase. Conserving biodiversity without jeopardising agricultural production will require the development of innovative technological and institutional options in association with policy and market interventions.  相似文献   

Effect of a new thermal treatment in combination with saprobic fungal incubation on the phytotoxicity level of alperujo     

Sampedro I  Aranda E  Rodríguez-Gutiérrez G  Lama-Muñoz A  Ocampo JA  Fernández-Bolaños J  García-Romera I 《Journal of agricultural and food chemistry》2011,59(7):3239-3245

Byproducts generated from food industries, such as olive oil mills, have been studied to decrease harmful pollution and their environmental consequences. In this work, a new thermal pretreatment and saprobic fungal incubation to detoxify alperujo (two-phase olive mill waste) have been evaluated in view of its use as fertilizer in agriculture. The sequential use of both methods simplifies the thermal conditions and incubation times of the fungal treatment. Optimization of the thermal treatment from 150 to 170 °C for 45 and 15 min, respectively, reduced the incubation time with Coriolpsis rigida from 20 to 10 weeks needed to reduce phytotoxic effects on tomato plants. Therefore, the combination of thermal and biological treatments will allow the development of the potential benefits of alperujo to improve nutrients in agricultural soil.  相似文献   

Quantification of 4-methylimidazole in class III and IV caramel colors: validation of a new method based on heart-cutting two-dimensional liquid chromatography (LC-LC)     

Moretton C  Crétier G  Nigay H  Rocca JL 《Journal of agricultural and food chemistry》2011,59(8):3544-3550

4-Methylimidazole (4MeI) is a nitrogen compound formed during the manufacture of class III and IV caramel colors. The European Commission has limited its content to 250 ppm. Two methods were compared to perform 4MeI quantification in caramels. The first one, currently used and considered to be the reference method, consists of a hot extraction of caramel color with dichloromethane and an analysis of the acetyl derivative of the extract by gas chromatography coupled to mass spectrometry (GC-MS). The second method is based on the heart-cutting two-dimensional liquid chromatography technique (LC-LC) to directly separate 4MeI from the other components present in caramel color sample (diluted in water) in <30 min. The accuracy profile validation method and the comparison between the results obtained with the two methods show that the new and completely automated LC-LC method is usable to quantify 4MeI in caramels.  相似文献   

In vitro digestibility of α-casozepine, a benzodiazepine-like peptide from bovine casein, and biological activity of its main proteolytic fragment     

Cakir-Kiefer C  Le Roux Y  Balandras F  Trabalon M  Dary A  Laurent F  Gaillard JL  Miclo L 《Journal of agricultural and food chemistry》2011,59(9):4464-4472

α-Casozepine is a peptide, corresponding to the sequence 91-100 of the bovine α(s1)-casein, displaying anxiolytic activity in the rat. The α(s1)-casein tryptic hydrolysate containing this peptide decreases stress effects after oral administration in various species including man. Therefore, the stability of this peptide toward gastric and pancreatic proteases has been assessed by using pepsin, chymotrypsin/trypsin, Corolase PP, pepsin followed by chymotrypsin/trypsin or pepsin followed by Corolase PP. α-Casozepine was slowly degraded by chymotrypsin, much more sensitive to pepsin and Corolase PP but not completely destroyed after 4 h kinetics. The bonds in the region 91 to 95 of the α-casozepine were totally resistant to hydrolysis by all studied proteases. Surprisingly, a fragment, corresponding to the sequence 91-97 and found in all the hydrolysis media in significant amount, possessed an anxiolytic activity in three behavioral tests measuring this parameter. This peptide could participate in the in vivo activity of α-casozepine.  相似文献   

Profiling LC-DAD-ESI-TOF MS method for the determination of phenolic metabolites from avocado (Persea americana)     

Hurtado-Fernández E  Carrasco-Pancorbo A  Fernández-Gutiérrez A 《Journal of agricultural and food chemistry》2011,59(6):2255-2267

A powerful HPLC-DAD-ESI-TOF MS method was established for the efficient identification of the chemical constituents in the methanolic extracts of avocado (Persea americana). Separation and detection conditions were optimized by using a standard mix containing 39 compounds belonging to phenolic acids and different categories of flavonoids, analytes that could be potentially present in the avocado extracts. Optimum LC separation was achieved on a Zorbax Eclipse Plus C18 analytical column (4.6×150 mm, 1.8 μm particle size) by gradient elution with water+acetic acid (0.5%) and acetonitrile as mobile phases, at a flow rate of 1.6 mL/min. The detection was carried out by ultraviolet-visible absorption and ESI-TOF MS. The developed method was applied to the study of 3 different varieties of avocado, and 17 compounds were unequivocally identified with standards. Moreover, around 25 analytes were tentatively identified by taking into account the accuracy and isotopic information provided by TOF MS.  相似文献   

Relationships between earthworm communities and burrow numbers under different land use systems     

G. Pérès  A. Bellido  P. Curmi  P. Marmonier  D. Cluzeau 《Pedobiologia》2011,54(1):37-44

This study addresses the influence of three different land use systems (continuous maize, pasture/maize rotation, permanent pasture) on the relationships between earthworm populations and the number of earthworm burrows quantified in a soil profile. Quantified burrows were limited to those observable by the naked eye (i.e. >2 mm in diameter) and enumerated earthworms were limited to those which could have created the observable burrows (i.e. >0.3 g).The results were combined with data from the literature coming from different geographical regions. This study showed that earthworm abundance decreased with the increasing land management intensity (maize crop vs. pasture), while the number of burrows could be higher or similar under maize compared to pasture. Under maize, despite lower earthworm abundance and the annual destruction of the burrows by tillage, the number of burrows was almost as high as under pasture. This absence of a relationship between burrow numbers and earthworm abundance was observed in the soil profile and for each layer of the profile for each land use system. Furthermore, the burrow number/m^?2 per earthworm strongly varied depending on land use and was far higher under maize when compared to pasture (74 vs. 7). Therefore, a power-law type relationship was clearly established between burrow number/m^?2 per earthworm and earthworm abundance. This power type relationship was also observed when including data from the literature although it followed a different mathematical model. These results were explained by (i) increased earthworm burrowing activity (i.e. an increase in the number of burrows produced by each earthworm) under maize, and (ii) the dynamics of burrow number under pasture (i.e. decreased burrowing activity and burrow destruction process); both results of food accessibility combined with inter-individual competition. The results of the study suggest that farmers should not use the number of pores as an indicator of earthworm abundance, but as an indicator of earthworm activity, which could be integrated in an indicator of soil quality.  相似文献