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31.
The bee genus Parapsaenythia Friese (Apidae, Protandrenini) is restricted to South America and characterized by the strongly punctate integument and hairy eyes. In the present work, the species of Parapsaenythia are revised, with seven species recognized, of which three are described as new: P. carinulata sp.n. (Argentina, Brazil, Paraguay), P. inornata Moure (Brazil), P. lanata sp.n. (Brazil), P. paspali (Schrottky) (Argentina, Brazil, Paraguay), P. puncticutis (Vachal) (Argentina, Bolivia), P. scutellaris sp.n. (Argentina, Bolivia, Brazil, Paraguay) and P. serripes (Ducke) (Argentina, Brazil). Lectotypes are designated for Psaenythia (Parapsaenythia) argentina Friese, Anthrenoides paspali Schrottky and Parapsaenythia paraguayae Brèthes. Floral records, distribution maps, illustrations and an identification key are provided. The cladistic analysis of 11 terminal species (all species of Parapsaenythia plus four outgroup species), based on 45 characters of external morphology and male terminalia, produced a single most parsimonious tree. Parapsaenythia was recovered as monophyletic, with the relationships among its species as follows: (P. inornata (P. carinulata sp.n. (P. lanata sp.n. (P. scutellaris sp.n. (P. serripes, P. paspali, P. puncticutis))))). Based on these relationships plus the available distributional data, a cladistic biogeographic analysis was performed, and area cladograms for the Chacoan subregion are presented and discussed. 相似文献
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JAN CHRISTIAN HABEL DENNIS RÖDDER THOMAS SCHMITT GABRIEL NÈVE 《Global Change Biology》2011,17(1):194-205
The climate warming of the postglacial has strongly reduced the distribution of cold‐adapted species over most of Central Europe. Such taxa have therefore become extinct over most of the lowlands and shifted to higher altitudes where they have survived to the present day. The lycaenid butterfly Lycaena helle follows this pattern of former widespread distribution and later restriction to mountain areas such as the European middle mountains. We sampled 203 individuals from 10 populations representing six mountain ranges (Pyrenees, Jura, Massif Central, Morvan, Vosges and Ardennes) over the species' western distribution. Allozyme and microsatellite polymorphisms were analysed to study the genetic status of these highly fragmented populations. Both molecular marker systems revealed a strong genetic differentiation among the analysed populations, coinciding with the orographic structure and highly restricted gene flow among them. The large‐scale genetic differentiation is more pronounced in allozymes (FCT: 0.326) than in microsatellites (RCT: 0.113), but microsatellites show a higher resolution on the regional scale (RSC: 0.082) compared with allozymes (FSC: n.s.). For both analytical tools, we found private alleles occurring exclusively in a single mountain area. The highly fragmented and isolated occurrence of populations is supported by the distribution pattern of potentially suitable climate suggested by species distribution models. Model projections under two climate warming scenarios predict a decline of climatically suitable areas, which will result in the extinction of most of the populations showing unique genetic characteristics. 相似文献
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GABRIEL YVON‐DUROCHER JOSÉ M. MONTOYA GUY WOODWARD J. IWAN JONES MARK TRIMMER 《Global Change Biology》2011,17(2):1225-1234
Methane (CH4) and carbon dioxide (CO2) are the dominant gaseous end products of the remineralization of organic carbon and also the two largest contributors to the anthropogenic greenhouse effect. We investigated whether warming altered the balance of CH4 efflux relative to gross primary production (GPP) and ecosystem respiration (ER) in a freshwater mesocosm experiment. Whole ecosystem CH4 efflux was strongly related to temperature with an apparent activation energy of 0.85 eV. Furthermore, CH4 efflux increased faster than ER or GPP with temperature, with all three processes having sequentially lower activation energies. Warming of 4 °C increased the fraction of GPP effluxing as CH4 by 20% and the fraction of ER as CH4 by 9%, in line with the offset in their respective activation energies. Because CH4 is 21 times more potent as a greenhouse gas, relative to CO2, these results suggest freshwater ecosystems could drive a previously unknown positive feedback between warming and the carbon cycle. 相似文献
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GABRIEL E. MACHOVSKY CAPUSKA SARAH L. DWYER MAURICE R. ALLEY KAREN A. STOCKIN DAVID RAUBENHEIMER 《Ibis》2011,153(3):631-635
Plunge‐diving is a highly successful strategy for dealing with the challenges confronting birds feeding on pelagic prey. We tested for evidence of fatal injuries due to collision between conspecifics in plunge‐diving Australasian Gannets Morus serrator and Cape Gannets Morus capensis, respectively, by performing post‐mortem examinations of carcasses recovered from New Zealand waters and analysing video footage of Cape Gannet foraging events from South Africa. We found evidence of accidental collisions between Gannets and also observed a case of attempted kleptoparasitism, in which a diving Cape Gannet targeted a previously captured fish in the beak of a conspecific. 相似文献
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Role of vegetation in determining carbon sequestration along ecological succession in the southeastern United States 总被引:2,自引:0,他引:2
PAUL C. STOY † GABRIEL G. KATUL†‡ MARIO B. S. SIQUEIRA†§ JEHN-YIH JUANG†¶ KIMBERLY A. NOVICK† HEATHER R. McCARTHY † A. CHRISTOPHER OISHI† RAM OREN† 《Global Change Biology》2008,14(6):1409-1427
Vegetation plays a central role in controlling terrestrial carbon (C) exchange, but quantifying its impacts on C cycling on time scales of ecological succession is hindered by a lack of long‐term observations. The net ecosystem exchange of carbon (NEE) was measured for several years in adjacent ecosystems that represent distinct phases of ecological succession in the southeastern USA. The experiment was designed to isolate the role of vegetation – apart from climate and soils – in controlling biosphere–atmosphere fluxes of CO2 and water vapor. NEE was near zero over 5 years at an early successional old‐field ecosystem (OF). However, mean annual NEE was nearly equal, approximately ?450 g C m?2 yr?1, at an early successional planted pine forest (PP) and a late successional hardwood forest (HW) due to the sensitivity of the former to drought and ice storm damage. We hypothesize that these observations can be explained by the relationships between gross ecosystem productivity (GEP), ecosystem respiration (RE) and canopy conductance, and long‐term shifts in ecosystem physiology in response to climate to maintain near‐constant ecosystem‐level water‐use efficiency (EWUE). Data support our hypotheses, but future research should examine if GEP and RE are causally related or merely controlled by similar drivers. At successional time scales, GEP and RE observations generally followed predictions from E. P. Odum's ‘Strategy of Ecosystem Development’, with the surprising exception that the relationship between GEP and RE resulted in large NEE at the late successional HW. A practical consequence of this research suggests that plantation forestry may confer no net benefit over the conservation of mature forests for C sequestration. 相似文献
39.
LEANDRO FREITAS GABRIEL BERNARDELLO LEONARDO GALETTO ADELITA A. S. PAOLI 《Botanical journal of the Linnean Society. Linnean Society of London》2001,136(3):267-277
Flower morphology, nectary structure, nectar chemical composition, breeding system, floral visitors and pollination were analysed in Croton sarcopetalus , a diclinous-monoecious shrub from Argentina. Male flowers have five receptacular nectaries, with no special vascular bundles, that consist of a uniserial epidermis with stomata subtended by a secretory parenchyma. Female flowers bear two different types of nectaries: inner (IN) and outer (ON) floral nectaries. IN, five in all, are structurally similar to the nectaries of male flowers. The five ON are vascularized, stalked, and composed of secretory, column-shaped epidermal cells without stomata subtended by secretory and ground parenchyma. In addition, ON act as post-floral nectaries secreting nectar during fruit ripening. Extrafloral nectaries (EFN) are located on petioles, stipules and leaf margins. Petiolar EFN are patelliform, stalked and anatomically similar to the ON of the female flower. Nectar sampled from all nectary types is hexose dominant, except for the ON of the female flower at the post-floral stage that is sucrose dominant. The species is self-compatible, but geitonogamous fertilization is rarely possible because male and female flowers are not usually open at the same time in the same individual, i.e. there is temporal dioecism. Flowers are visited by 22 insect species, wasps being the most important group of pollinators. No significant differences were found in fruit and seed set between natural and hand pollinated flowers. This pattern indicates that fruit production in this species is not pollen/pollinator limited and is mediated by a wide array of pollinators. 相似文献
40.
Abstract. It has been shown that atmospheric O2 can either depress or stimulate the rate of apparent photosynthesis of white mustard depending on the environmental conditions: CO2 concentration, light intensity and temperature. Stimulation by O2 was observed only under high photon fluence rate and at high CO2 concentrations. The critical CO2 concentration below which O2 was inhibiting and above which it was stimulating was dependent on the temperature of the assay: for plants grown at 12°C the critical CO2 concentration was 13.35 mmol at 5° C and 21.92 mmol at 10° C. Stimulation by O2 depended also on the growth temperature: for measurements at 26.31 mmol m?3 CO2, O2 was stimulating at temperatures less than 12°C for plants grown at 12°C and less than 19°C for plants grown at 27°C. The efficiency of the O2-dependent stimulation of net photosynthesis was maximum at 9.21 mol m?3 O2 at 26.31 mmol m?3 CO2. Oxygen-stimulation of net photosynthesis was detected in Nicotiana tabacum L. var Samsun, Lycopersicum esculentum L. and Chenopodium album L. At 5°C and under high photon fluence rate, O2 increased the carboxylation capacity of the photosynthetic apparatus of mustard and decreased its affinity for CO2. The O2 inhibition of the net CO2 uptake observed at low CO2 concentrations was the result of a decrease in the affinity for carbon dioxide. The nature of the mechanism which causes the stimulation of photosynthesis is discussed. 相似文献