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1.
Summary The sequential steps in the behavioral process of a California stock of the entomophagous parasite,Venturia canescens (Grav.), parasitizingAnagasta kühniella (Zeller) was studied.
In host-habitat finding, food media infested with hosts were very attractive to the parasites.
Host finding was not covered in detail in this paper as it is presented in subsequent papers. Briefly, in all experiments
host density was the most influential factor affecting the efficiency of the parasite.
When three age stages of the host were exposed to a parasite, all tests showed that the large, last instar larvae was the
preferred age stage but it was not the most suitable (when parasitized) for successful parasite development. Small larvae
were less preferred but more suitable for parasite development when accepted.
These studies were conducted as a partial fulfillment in the Ph. D. program of one of us (B. M. Matsumoto) and form a part of a broad investigation into the processes operating in the dynamics of arthropod populations under grants
toC. B. Huffaker from the U. S. Public Health Service, National Institutes of Health and the U. S. Department of Agriculture. 相似文献
2.
《Fungal Ecology》2018
The genera Dicymbe and Aldina (Fabaceae) host ectomycorrhizal fungi (EcM) and are common in white sand forests (WSFs), a highly specialized habitat with a high level of plant endemism compared with terra-firme forests. In this study, we visited four times a 1-ha permanent plot established in a small patch of a WSF in the south of Colombia Amazonia. Forty-eight species of EcM fungi were recovered from sporocarps and 15 ITS species-level were detected from root tips. Seventeen species were new reports to Colombia and seven corresponded to undescribed species. These results confirm that this WSF supports a significant EcM fungal diversity. Most of the species found in this study have been previously reported to be associated with other legume and/or dipterocarp species from geographically distant forests. The long-distance occurrence combined with low host specificity, suggest the possibility of gene flow between geographically distant populations of EcM fungi in neotropical lowland rainforests. 相似文献
3.
A method is proposed to analyse the dispersion profiles of species in classes of environmental variables, based on the decomposition of the expected frequencies in contingency tables with many interacting species. The method has been applied to data of dominant or very frequent graminoid species in grasslands of the Natisone Valley (Friuli, Italy). It allowed to make predictions by removing the random component of variation.Nomenclature follows: P. Zangheri (1976). Flora Italica, CEDAM, Padua.The authors were recipients of an Italian CNR grant (E. Feoli) and a Canadian NSERC grant (L. Orlóci) during tenure of this project. The results are in partial fulfillment of a commitment to the Centro Regionale per la Sperimentazione Agraria per il Friuli-Venezia Giulia. 相似文献
4.
A semi-fluorinated hybrid amphiphile, pentadecafluoro-5-dodecyl (F7H4) sulfate, has been shown to form reversed micelles in dense CO2; the aggregates evolve to form water-in-CO2 (w/c) microemulsion droplets on addition of water. Aggregation structures in these w/c phases have been characterised by small-angle neutron scattering (SANS), showing the presence of cylindrical droplets, which change into dispersed lamellar phases at even higher water loadings. Other systems are also introduced, being high internal phase emulsions (HIPEs) with brine, and liquid and supercritical CO2, stabilized by certain commercially available nonylphenol ethoxylates (Dow Tergitol NP-, and Huntsman Surfonic N- amphiphiles). These dispersions have been characterised by SANS for the first time. Quantitative analyses of the HIPEs SANS profiles show that they behave similarly to hydrocarbon-water emulsion analogues, with regard to total interfacial areas and the effects of amphiphile concentration on the underlying structures. Finally, the advantages and disadvantages of both approaches for controlling the physico-chemical properties of liquid/supercritical CO2 in potential applications are compared and contrasted. These results highlight the importance of using specially designed CO2-philic amphiphiles for generating self-assembly structures in dense CO2. 相似文献
5.
Because estuaries are dynamic on many temporal scales, it is difficult to differentiate long-term shifts from those resulting from erratic pulse events like severe storms. Diatoms are abundant and diverse in estuaries, and may characterize these dynamics across relevant time scales. The climate of south Florida is subtropical, with dry winters and wet summers that may also harbor tropical storms and cyclones. We investigated whether these repeated seasonal drivers of change in estuaries differ from the influence of tropical cyclones on planktonic and benthic diatom assemblages. Diatom assemblages and environmental parameters were measured in the Charlotte Harbor watershed of southwest Florida to identify differences between the wet and dry seasons and changes that occurred following Tropical Storm Debby in 2012. Indicator taxa that were significantly affiliated with each season and post-storm conditions were identified. Diatom assemblages across the watershed were similar in wet and dry seasons, but differences increased following the tropical storm. The reduction in community dispersion following the storm was pronounced in each of the major drainages of the estuary. There were spatially-distinct responses of diatoms to environmental changes driven by the storm. These results suggest that past storm activity could be detected using diatoms preserved in estuarine sediments using both single indicator-species as well as community approaches. 相似文献
6.
We analyze a discrete-time model of populations that grow and disperse in separate phases. The growth phase is a nonlinear process that allows for the effects of local crowding. The dispersion phase is a linear process that distributes the population throughout its spatial habitat. Our study quantifies the issues of survival and extinction, the existence and stability of nontrivial steady states, and the comparison of various dispersion strategies. Our results show that all of these issues are tied to the global nature of various model parameters. The extreme strategies of staying-in place and going-everywhere-uniformly are compared numerically to diffusion strategies in various contexts. We approach the mathematical analysis of our model from a functional analysis and an operator theory point of view. We use recent results from the theory of positive operators in Banach lattices. 相似文献
7.
Abstract Roder, W.; Feyerabend, G.; Rogoll, H.: Landwirtschaftlicher Pflanzenschutz. 560 S., 217 Abb. Berlin: VEB Dt. Landwirtschaftsverlag, 1975. Reviewed by D. Spaar. Libbert, E. (Hrsg.): Kompendium der allgemeinen Biologie. 1. Aufl. 474 S., 179 Abb., 12 Tab. Jena: VEB Gustav Fischer Verlag, 1976. Reviewed by J. Richter. Kllinkowski, M.; Mühle, E.; Reinmuth, E.; Bochow, H.: Phytopathologie und Pflanzenschutz. 2., überarbeitete u. erweiterte Aufl. 3. Bd. 914 S., 523 Abb. Berlin: Akademie-Verlag, 1976. Reviewed by D. Spaar. Börner, H.: Pflanzenkrankheiten und Pflanzenschutz. 2., überarb. Aufl., 419 S., 74 Abb. Stuttgart: Eugen Ulmer, 1975. Reviewed by W. Lehmann. 相似文献
8.
9.
The bacterial phosphotransferase system (PTS) is a signal transduction pathway that couples phosphoryl transfer to active sugar transport across the cell membrane. The PTS is initiated by the binding of phosphoenolpyruvate (PEP) to the C-terminal domain (EIC) of enzyme I (EI), a highly conserved protein that is common to all sugar branches of the PTS. EIC exists in a dynamic monomer/dimer equilibrium that is modulated by ligand binding and is thought to regulate the overall PTS. Isolation of EIC has proven challenging, and conformational dynamics within the EIC domain during the catalytic cycle are still largely unknown. Here, we present a robust protocol for expression and purification of recombinant EIC from Escherichia coli and show that isolated EIC is capable of hydrolyzing PEP. NMR analysis and residual dipolar coupling measurements indicate that the isolated EIC domain in solution adopts a stable tertiary fold and quaternary structure that is consistent with previously reported crystallographic data. NMR relaxation dispersion measurements indicate that residues around the PEP binding site and in the β3α3 turn (residues 333-366), which is located at the dimer interface, undergo a rapid transition on the sub-millisecond time scale (with an exchange rate constant of ~1500 s(-1)) between major open (~97%) and minor closed (~3%) conformations. Upon PEP binding, the β3α3 turn is effectively locked in the closed state by the formation of salt bridges between the phosphate group of PEP and the side chains of Lys(340) and Arg(358), thereby stabilizing the dimer. 相似文献
10.
Soil organic matter and structural stability: mechanisms and implications for management 总被引:61,自引:5,他引:61
J. M. Oades 《Plant and Soil》1984,76(1-3):319-337
Summary The stability of pores and particles is essential for optimum growth of plants. Two categories of aggregates macro- (> 250 m) and micro- (<250 m) depend on organic matter for stability against disruptive forces caused by rapid wetting. Dispersion of clay particles from microaggregates is promoted by adsorption of complexing organic acids which increase the negative charge on clays. The acids are produced by plants, bacteria and fungi. However, the dispersibility of clay in microaggregates is offset by the binding action of polysaccharides, mainly mucilages produced by bacteria, but also by plant roots and fungal hyphae. The stability of microaggregates is also enhanced by multivalent cations which act as bridges between organic colloids and clays. Macroaggregates are enmeshed by plant roots, both living and decomposing, and are thus sensitive to management, and increase in number when grasses are grown and the soil is not disturbed. Lack of root growth,i.e. fallow, has the opposite effect. Various implications for management of soil structure are discussed.Introductory lecture 相似文献