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1.
Abstract 1. The majority of general life‐history models treat the environment as being invariable through time, even though temporal variation in selective agents could dramatically change the outcomes, e.g. in terms of optimal size and time at maturity. For herbivorous insects, seasonal differences in food quality are reasonably well described, but seasonal dynamics of top‐down selective forces are poorly documented. 2. The present study attempted to quantify seasonal changes in predation risk of folivorous insect larvae in temperate forest habitats. In a series of field experiments, artificial larvae were exposed to predators, and the resulting bird‐inflicted damage was recorded. The trials were repeated regularly throughout the course of two summers. 3. A distinct peak of larval mortality was recorded in mid‐June (the nestling period for most insectivorous passerine birds), after which predation risk declined to a plateau of 20–30% below the peak value. 4. The recorded pattern is interpreted as a consequence of seasonal changes in the number and behaviour of insectivorous birds, and the abundance of alternative food resources for these predators. 5. A quantitative analysis based on field data indicated that considering temporal variation in mortality in life‐history models is crucial for obtaining realistic predictions concerning central life‐history traits, such as final body size in different generations. 相似文献
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PETER JOHNSTON 《Zoological Journal of the Linnean Society》2011,163(3):959-982
There has been little agreement on the phylogeny of palaeognathous birds, with major differences amongst and between results from morphological and molecular data. Two recently published phylogenies using nuclear and mitochondrial DNA have substantial agreement in overall topology, with the ostrich as sister group of all other extant palaeognaths and a kiwi‐emu‐cassowary clade. Here I report a morphological phylogeny based mainly on new characters from the tongue apparatus and cranial osteology, with a theoretical ancestor as outgroup. A new interpretation of the evolution of the avian palate is included. This phylogeny is very similar to these recent molecular results; this is the first report of such congruence, and offers a credible basis for understanding the evolution of this clade. This phylogeny is fully consistent with a Gondwana vicariance model of evolution. Dates attributed from known geological events place the first extant radiation (ostrich) in the mid‐Cretaceous, and offer a means of calibration of future molecular clock investigations. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 959–983. 相似文献
4.
Abstract Growth of barley (Hordeum vulgare L., cv. Georgie) was insensitive to soil K content above about 150 mg kg?1, but at lower levels it declined. The reduction in yield was greater in soils containing approximately 10 mg Na kg?1 than in soils with about 90 mg kg?1 of Na. Growth was unaffected by changes in shoot K concentration above 75 mol m?3, but declined at lower concentrations, and the decrease was less in plants grown in soils with high Na. Growth responses were not simply related to tissue K concentrations because plants grown in soils with extra Na had higher yields but lower K concentrations. When soil Na was low, plants accumulated Ca as tissue K declined, but when Na was provided this ion was accumulated. Plant Mg concentrations were generally low but increased as K decreased. The Ca and Mg were osmotically active. There were highly significant inverse linear relationships between yield and either the Ca or Mg concentrations in the shoots. X-ray microanalysis was used to examine the compartmentation of cations in leaves from barley plants (cv. Clipper) grown in nutrient solutions with high and low K concentrations. In plants grown with 2.5 mol m?3 K, this was the major cation in both the cytoplasm and vacuole of mesophyll cells. However, in plants grown with 0.02 mol m?3 K it declined to undetectable levels in the vacuole, although it was still detectable in the cytoplasm. In all plants, Ca was mainly located in epidermal cells. The implication of the results for explaining responses to K. in terms of compartmentation of solutes is discussed. 相似文献
5.
A Phialophora sp. (isolate I-52), originally isolated from soil in a wheat field exhibiting suppression of take-all disease caused by Gaeumannomyces graminis var. tritici , was tested under field conditions for its ability to suppress this disease in winter and spring wheat. I-52 was grown on a variety of autoclaved organic substrates, including oat, millet and canola seed. All of these gave significant disease control when added to the seed furrow with inoculum of the take-all fungus. W hole seed of I-52 substrate was as effective as particles < 0.5 mm in diameter. Placing I-52 in powdered form directly on to wheat seed was ineffective in controlling take-all. Rates as low as 2 g of I-52/3.3 m of row added with the seed provided some control of take-all, and nearly complete control in winter wheat was obtained using 15 g/3.3 m. The winter wheat host cultivar did not influence the degree of control of take-all by I-52. 相似文献
6.
The absorption of peptides 总被引：2，自引：0，他引：2
7.
A Protein from Immature Raspberry Fruits which Inhibits Endopolygalacturonases from Botrytis cinerea and other Micro-organisms 总被引：2，自引：0，他引：2
A polygalacturonase-inhibiting protein (PGIP) was purified fromimmature raspberry fruits using ion exchange chromatography.The protein was composed of a single polypeptide chain withMr of 38·5 kDa and a pI residing above pH 10. Kineticstudies suggested that the inhibition was of a non-competitivenature. The PGIP inhibited two endopolygalacturonases (endo-PG)purified from Botrytis cinerea and an endo-PG produced by Aspergillusniger to varying degrees but did not inhibit two exo-PGs purifiedfrom B. cinerea, bacterial endopectate lyases and bacterialendo-PGs. The concentration of PGIP at various stages of flowerand fruit development was determined. The inhibitor was notdetected in the flower, but reached a maximum of 69 units g–1in the immature green fruit decreasing to 9 units g–1as fruits matured. The N-terminal amino-acid sequence was determined. Key words: Polygalacturonase-inhibiting protein, Rubus idaeus, red raspberry, Botrytis cinerea, pectinases 相似文献
8.
A. URBANEK M. PIOTROWICZ R. SZADZIEWSKI W. GI ŁKA 《Medical and veterinary entomology》2014,28(4):355-363
The distribution and morphology of antennal sensilla coeloconica in parasitic and predaceous biting midges were studied in females of Forcipomyia (feeding on the blood of frogs), Atrichopogon (feeding on haemolymph), Austroconops, Culicoides (feeding on the blood of birds and mammals) and Brachypogon (feeding on haemolymph and dissolved tissues of insects) (all: Diptera: Ceratopogonidae). A Lower Cretaceous female of Archiculicoides (Diptera: Ceratopogonidae) from Lebanese amber, which fed on the blood of unknown vertebrates, was also examined. In sensilla coeloconica ringed by microtrichia, the peg is grooved longitudinally and protrudes distinctly from the pit. We suggest that the microtrichia encircling the protruding peg form a structure resembling a picket fence in order to maintain a higher level of humidity, which facilitates the capture and transport of odour molecules through the channels in the peg wall. Sensilla coeloconica ringed by microtrichia function as very effective chemoreceptors in host‐ and prey‐seeking activity. During the evolution of Ceratopogonidae, sensilla coeloconica with a fence of microtrichia have evolved twice in groups feeding on the blood of vertebrates (i.e. in the basal lineage: Lower Cretaceous or earlier) and in the subgenus Lasiohelea of Forcipomyia (Palaeogene). Sensilla coeloconica ringed by microtrichia are described for the first time in the relict genus Austroconops. 相似文献
9.
Miniature collar-type transmitters originally designed by W.W. Cochran, Illinois, were adapted for use on timber wolves(Canis lupus sp.) in east-central Ontario. Wild timber wolveswere captured in steel traps, restrained with a forked stick,fitted with radio-collars and released at point of capture.Receivers were adapted for use in trucks, airplanes, and forwalking in rough bush country. Maximum ranges were 3.2 km withground and 9.6 km with aircraft receivers. A preadult femaletagged in July, 1964, and a lactating adult female tagged inJune, 1965, were tracked intermittently for 5.5 and 2.5 months,respectively. Tracking periods for six other animals of bothsexes, ranging in age from pups to adults, varied from 2 daysto 4 months. The lactating female and her associated pack regularlyreturned to three preferred "resting sites" for various periodsduring July and August. Preferred areas were well drained, semi-open,mixed conifer-hardwood stands in close proximity to swamps orbeaver ponds. The preadult female ranged in an area frequentedby a pack, but frequently remained independent of it. A preadultmale, tagged in the same region, wandered over a slightly largerarea than the female. Tagged animals were active throughoutall periods of the day or night. Activity increased slightlyduring the early evening hours. There was a slight correlationbetween weather conditions and patterns of behavior and activity.Apparently, tagged individuals were quickly accepted by othermembers of the pack. 相似文献
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