Garcia-Forner N., Adams H.D., Sevanto S., Collins A.D., Dickman L.T., Hudson P.J., Zeppel M.J., Jenkins M.W., Powers H., Martinez-Vilalta J., Mcdowell N.G. (2015) Responses of two semiarid conifer tree species to reduced precipitation and warming reveal new perspectives for stomatal regulation. Plant, Cell and Environment. : 0-0.LinkDoi: 10.1111/pce.12588
Relatively anisohydric species are predicted to be more predisposed to hydraulic failure than relatively isohydric species, as they operate with narrower hydraulic safety margins. We subjected co-occurring anisohydric Juniperus monosperma and isohydric Pinus edulis trees to warming, reduced precipitation, or both, and measured their gas exchange and hydraulic responses. We found that reductions in stomatal conductance and assimilation by heat and drought were more frequent during relatively moist periods, but these effects were not exacerbated in the combined heat and drought treatment. Counter to expectations, both species exhibited similar gs temporal dynamics in response to drought. Further, whereas P.edulis exhibited chronic embolism, J.monosperma showed very little embolism due to its conservative stomatal regulation and maintenance of xylem water potential above the embolism entry point. This tight stomatal control and low levels of embolism experienced by juniper refuted the notion that very low water potentials during drought are associated with loose stomatal control and with the hypothesis that anisohydric species are more prone to hydraulic failure than isohydric species. Because direct association of stomatal behaviour with embolism resistance can be misleading, we advocate consideration of stomatal behaviour relative to embolism resistance for classifying species drought response strategies. © 2015 John Wiley & Sons Ltd.
Gargallo-Garriga A., Sardans J., Perez-Trujillo M., Oravec M., Urban O., Jentsch A., Kreyling J., Beierkuhnlein C., Parella T., Penuelas J. (2015) Warming differentially influences the effects of drought on stoichiometry and metabolomics in shoots and roots. New Phytologist. : 0-0.LinkDoi: 10.1111/nph.13377
Plants in natural environments are increasingly being subjected to a combination of abiotic stresses, such as drought and warming, in many regions. The effects of each stress and the combination of stresses on the functioning of shoots and roots have been studied extensively, but little is known about the simultaneous metabolome responses of the different organs of the plant to different stresses acting at once. We studied the shift in metabolism and elemental composition of shoots and roots of two perennial grasses, Holcus lanatus and Alopecurus pratensis, in response to simultaneous drought and warming. These species responded differently to individual and simultaneous stresses. These responses were even opposite in roots and shoots. In plants exposed to simultaneous drought and warming, terpenes, catechin and indole acetic acid accumulated in shoots, whereas amino acids, quinic acid, nitrogenous bases, the osmoprotectants choline and glycine betaine, and elements involved in growth (nitrogen, phosphorus and potassium) accumulated in roots. Under drought, warming further increased the allocation of primary metabolic activity to roots and changed the composition of secondary metabolites in shoots. These results highlight the plasticity of plant metabolomes and stoichiometry, and the different complementary responses of shoots and roots to complex environmental conditions. © 2015 New Phytologist Trust.
Gibb H., Sanders N.J., Dunn R.R., Watson S., Photakis M., Abril S., Andersen A.N., Angulo E., Armbrecht I., Arnan X., Baccaro F.B., Bishop T.R., Boulay R., Castracani C., Del Toro I., Delsinne T., Diaz M., Donoso D.A., Enriquez M.L., Fayle T.M., Feener D.H., Fitzpatrick M.C., Gomez C., Grasso D.A., Groc S., Heterick B., Hoffmann B.D., Lach L., Lattke J., Leponce M., Lessard J.-P., Longino J., Lucky A., Majer J., Menke S.B., Mezger D., Mori A., Munyai T.C., Paknia O., Pearce-Duvet J., Pfeiffer M., Philpott S.M., De Souza J.L.P., Tista M., Vasconcelos H.L., Vonshak M., Parr C.L. (2015) Climate mediates the effects of disturbance on ant assemblage structure. Proceedings of the Royal Society B: Biological Sciences. 282: 0-0.LinkDoi: 10.1098/rspb.2015.0418
Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about howclimate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages, we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effectwas manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 98C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk. © 2015 The Author(s) Published by the Royal Society. All rights reserved.
Gil-Tena A., De Caceres M., Ernoult A., Butet A., Brotons L., Burel F. (2015) Agricultural landscape composition as a driver of farmland bird diversity in Brittany (NW France). Agriculture, Ecosystems and Environment. 205: 79-89.LinkDoi: 10.1016/j.agee.2015.03.013
In agriculture-dominated landscapes, agricultural intensification and associated landscape homogenization have caused large declines in farmland biodiversity. This study was aimed at determining how agricultural landscape composition drives community diversity and composition of farmland birds in the characteristic bocage landscape in Brittany (NW France) on a broad scale. Using bird atlas data from the region (2004-2008; 10. ×. 10. km), we analyzed the importance of different components of agricultural landscape composition (types of crops, amount of semi-natural covers and elements, and artificial lands) on the alpha diversity and beta diversity of farmland birds of different functional groups, defined depending on the degree of farmland specialization and ecological requirements.Agricultural landscape composition features explained a small amount of variation in alpha and beta diversity, particularly for specialists and residents. Cereal crops were negatively correlated with alpha diversity of all the functional groups considered whereas rotational grasslands were negatively associated with migrant and insectivorous alpha diversity. Although shrublands are not common in Brittany, they were positively associated with the occurrence of some species and particularly with alpha diversity of all the functional groups but specialists and residents. At the spatial grain of analysis, community composition was mainly driven by a gradient of alteration of the bocage.To conclude, we claim for the consideration of regional idiosyncrasies in far-reaching planning schemes to prevent future biodiversity loss in agriculture-dominated landscapes due to agricultural intensification. In view of the observed large-scale trends gathered from atlas data analysis and the small amount of explained variation, we also advocate for subsequent finer scale bespoke surveys to determine the biodiversity status associated with the valuable bocage agricultural landscape. © 2015 Elsevier B.V.
Girado-Beltran P., Andreu J., Pino J. (2015) Exploring changes in the invasion pattern of alien flora in Catalonia (NE of Spain) from large datasets. Biological Invasions. 17: 3015-3028.LinkDoi: 10.1007/s10530-015-0930-3
Plant invasions are characterized by their dynamism, but they are generally described at a precise time step due to the dearth of datasets on species distribution across time. In this paper we employed specific alien plant databases to assess the factors associated with recent changes in plant invasion patterns in Catalonia from two perspectives, site and species. We gathered records of neophyte plant species per 10-km UTM cell from two spatially coincident large-scale datasets collected in 1989 and 2012. We estimated the richness increase of species per UTM cell and the range size increase of each species (i.e. the number of occupied UTM cells) between these dates. We then evaluated the association of richness increase with geographic, climatic and landscape factors, and that of range size increase with species traits and the characteristics of the introduction event. We found 401 species, 291 recorded up to 1989 and 110 afterwards. Richness increase was concentrated in new hotspots compared to those observed in 1989, suggesting that patterns of susceptibility to plant invasion have changed in recent decades. Climatic factors were the most important in determining the large-scale pattern of alien species, with the highest values of species richness increase in warmest and rainiest areas. Range size increase of each alien species was mostly explained by the historical range size, the introduction pathway, namely unintentional introductions and the interaction between habitat and the minimum residence time. These factors were more influential than species traits in the recent spread of alien plant species across the region. © 2015, Springer International Publishing Switzerland.
Giraudeau M., Mateos-Gonzalez F., Cotin J., Pagani-Nunez E., Torne-Noguera A., Senar J.C. (2015) Metal exposure influences the melanin and carotenoid-based colorations in great tits. Science of the Total Environment. 532: 512-516.LinkDoi: 10.1016/j.scitotenv.2015.06.021
Metals are naturally found in the environment but are also emitted through anthropogenic activities, raising some concerns about the potential deleterious effects of these elements on wildlife. The potential effects of metals on bird coloration have been the focus of several recent studies since animal colored-signals often reflect the physiology of their bearers and are thus used by animals to assess the quality of another individual as a mate or competitor. These studies have shown that the melanin pigmentation seems to be positively associated and the carotenoid-based coloration negatively associated with metal exposure in wild birds. Although these studies have been very useful to show the associations between metal exposure and coloration, only few of them have actually quantified the levels of metal exposure at the individual level; always focusing on one or two of them. Here, we measured the concentrations of eight metals in great tits' feathers and then assessed how these levels of metals were associated with the carotenoid and melanin-based colorations. We found that the melanin pigmentation was positively associated with the copper concentration and negatively correlated with the chromium concentration in feathers. In addition, we have shown that the carotenoid-based coloration was negatively associated with the feather's mercury concentration. This study is the first one to identify some metals that might affect positively and negatively the deposition of melanin and carotenoid into the plumage of wild birds. © 2015 Elsevier B.V.
Gleason S.M., Westoby M., Jansen S., Choat B., Hacke U.G., Pratt R.B., Bhaskar R., Brodribb T.J., Bucci S.J., Cao K.-F., Cochard H., Delzon S., Domec J.-C., Fan Z.-X., Feild T.S., Jacobsen A.L., Johnson D.M., Lens F., Maherali H., Martinez-Vilalta J., Mayr S., Mcculloh K.A., Mencuccini M., Mitchell P.J., Morris H., Nardini A., Pittermann J., Plavcova L., Schreiber S.G., Sperry J.S., Wright I.J., Zanne A.E. (2015) Weak tradeoff between xylem safety and xylem-specific hydraulic efficiency across the world's woody plant species. New Phytologist. : 0-0.LinkDoi: 10.1111/nph.13646
The evolution of lignified xylem allowed for the efficient transport of water under tension, but also exposed the vascular network to the risk of gas emboli and the spread of gas between xylem conduits, thus impeding sap transport to the leaves. A well-known hypothesis proposes that the safety of xylem (its ability to resist embolism formation and spread) should trade off against xylem efficiency (its capacity to transport water). We tested this safety-efficiency hypothesis in branch xylem across 335 angiosperm and 89 gymnosperm species. Safety was considered at three levels: the xylem water potentials where 12%, 50% and 88% of maximal conductivity are lost. Although correlations between safety and efficiency were weak (r2
Gomez-Polo P., Alomar O., Castane C., Aznar-Fernandez T., Lundgren J.G., Pinol J., Agusti N. (2015) Understanding trophic interactions of Orius spp. (Hemiptera: Anthocoridae) in lettuce crops by molecular methods. Pest Management Science. : 0-0.LinkDoi: 10.1002/ps.3989
BACKGROUND: The aphid Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae) and the thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) are common pests in Mediterranean lettuce crops, where Orius spp. are common generalist predators. Predation by Orius spp. was studied in a lettuce plot by conventional polymerase chain reaction (PCR) and real-time PCR analyses using specific primers of both main pests. Also, high-throughput sequencing was used to have a wider approach of the diet of these predators in natural field conditions. RESULTS: Molecular analyses indicated a higher predation on N. ribisnigri in spring and on F. occidentalis in summer. Predation on alternative prey, like Collembola, was also found in both seasons. Real-time PCR was more sensitive than conventional PCR in showing the target trophic links, whereas high-throughput sequencing revealed predation on other natural enemies - intraguild predation (IGP), showing other trophic interactions of Orius majusculus within the studied ecosystem. CONCLUSIONS: This study gives important information about the trophic relationships present in Mediterranean lettuce crops in different periods of the year. The detected predation by Orius spp. on alternative prey, as well as on other natural enemies, should be further investigated to clarify whether it adds or detracts to the biological control of N. ribisnigri and F. occidentalis. © 2015 Society of Chemical Industry.
Gomez-Polo P., Alomar O., Castane C., Lundgren J.G., Pinol J., Agusti N. (2015) Molecular assessment of predation by hoverflies (Diptera: Syrphidae) in Mediterranean lettuce crops. Pest Management Science. 71: 1219-1227.LinkDoi: 10.1002/ps.3910
BACKGROUND: Hoverflies (Diptera: Syrphidae) are generalist predators of a great variety of pests. Nasonovia ribisnigri (Hemiptera: Aphididae) and Frankliniella occidentalis (Thysanoptera: Thripidae) are two common pests in Mediterranean lettuce crops, where they occur alongside alternative prey (e.g. Collembola). A semi-field experiment was conducted in an experimental lettuce plot where hoverfly predation on N. ribisnigri, F. occidentalis and Collembola was studied by conventional PCR and qPCR using specific primers, as well as by next-generation sequencing (NGS) in order to reveal other potential trophic interactions. RESULTS: Trophic linkages between hoverflies and N. ribisnigri were the strongest both in spring and summer. F. occidentalis and Collembolans were also detected in both seasons, but with less frequency. qPCR detected a higher frequency of consumption than conventional PCR when both tests were run at optimal conditions. NGS analyses showed intraguild predation on other hoverfly species, as well as on anthocorids, spiders and even aphid parasitoids. CONCLUSIONS: Conventional PCR and qPCR provided important insights into Mediterranean hoverfly species predation on target pest and non-pest prey. NGS gave a complementary approach revealing a broader diet of these predators within the studied ecosystem. © 2014 Society of Chemical Industry.
Gonzalez-Olabarria J.R., Mola-Yudego B., Coll L. (2015) Different factors for different causes: Analysis of the spatial aggregations of fire ignitions in catalonia (Spain). Risk Analysis. : 0-0.LinkDoi: 10.1111/risa.12339
The present study analyzes the effects of different socioeconomic factors on the frequency of fire ignition occurrence, according to different original causes. The data include a set of documented ignition points in the region of Catalonia for the period 1995-2008. The analysis focused on the spatial aggregation patterns of the ignitions for each specific ignition cause. The point-based data on ignitions were interpolated into municipality-level information using kernel methods as the basis for defining five ignition density levels. Afterwards, the combination of socioeconomic factors influencing the ignition density levels of the municipalities was analyzed for each documented cause of ignition using a principal component analysis. The obtained results confirmed the idea that both the spatial aggregation patterns of fire ignitions and the factors defining their occurrence were specific for each of the causes of ignition. Intentional fires and those of unknown origin were found to have similar spatial aggregation patterns, and the presence of high ignition density areas was related to high population and high unemployment rates. Additionally, it was found that fires originated from forest work, agricultural activities, pasture burning, and lightning had a very specific behavior on their own, differing from the similarities found on the spatial aggregation of ignitions originated from smokers, electric lines, machinery, campfires, and those of intentional or unknown origin. © 2015 Society for Risk Analysis.
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