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31.
The topology of ecological interaction webs holds important information for theories of coevolution, biodiversity, and ecosystem stability . However, most previous network analyses solely counted the number of links and ignored variation in link strength. Because of this crude resolution, results vary with scale and sampling intensity, thus hampering a comparison of network patterns at different levels . We applied a recently developed quantitative and scale-independent analysis based on information theory to 51 mutualistic plant-animal networks, with interaction frequency as measure of link strength. Most networks were highly structured, deviating significantly from random associations. The degree of specialization was independent of network size. Pollination webs were significantly more specialized than seed-dispersal webs, and obligate symbiotic ant-plant mutualisms were more specialized than nectar-mediated facultative ones. Across networks, the average specialization of animal and plants was correlated, but is constrained by the ratio of plant to animal species involved. In pollination webs, rarely visited plants were on average more specialized than frequently attended ones, whereas specialization of pollinators was positively correlated with their interaction frequency. We conclude that quantitative specialization in ecological communities mirrors evolutionary trade-offs and constraints of web architecture. This approach can be easily expanded to other types of biological interactions. 相似文献
32.
Suh GS Ben-Tabou de Leon S Tanimoto H Fiala A Benzer S Anderson DJ 《Current biology : CB》2007,17(10):905-908
How specific sensory stimuli evoke specific behaviors is a fundamental problem in neurobiology. In Drosophila, most odorants elicit attraction or avoidance depending on their concentration, as well as their identity [1]. Such odorants, moreover, typically activate combinations of glomeruli in the antennal lobe of the brain [2-4], complicating the dissection of the circuits translating odor recognition into behavior. Carbon dioxide (CO2), in contrast, elicits avoidance over a wide range of concentrations [5, 6] and activates only a single glomerulus, V [5]. The V glomerulus receives projections from olfactory receptor neurons (ORNs) that coexpress two GPCRs, Gr21a and Gr63a, that together comprise a CO2 receptor [7-9]. These CO2-sensitive ORNs, located in the ab1 sensilla of the antenna, are called ab1c neurons [10]. Genetic silencing of ab1c neurons indicates that they are necessary for CO2-avoidance behavior [5]. Whether activation of these neurons alone is sufficient to elicit this behavior, or whether CO2 avoidance requires additional inputs (e.g., from the respiratory system), remains unclear. Here, we show that artificial stimulation of ab1c neurons with light (normally attractive to flies) elicits the avoidance behavior typical of CO2. Thus, avoidance behavior appears hardwired into the olfactory circuitry that detects CO2 in Drosophila. 相似文献
33.
The paper presents a set of two-dimensional experiments that utilize direct 13C detection to provide proton–carbon, carbon–carbon and carbon–nitrogen correlations in the bases of nucleic acids. The set
includes a 13C-detected proton–carbon correlation experiment for the measurement of 13C–13C couplings, the CaCb experiment for correlating two quaternary carbons, the HCaCb experiment for the 13C–13C correlations in cases where one of the carbons has a proton attached, the HCC-TOCSY experiment for correlating a proton
with a network of coupled carbons, and a 13C-detected 13C–15N correlation experiment for detecting the nitrogen nuclei that cannot be detected via protons. The IPAP procedure is used
for extracting the carbon–carbon couplings and/or carbon decoupling in the direct dimension, while the S3E procedure is preferred in the indirect dimension of the carbon–nitrogen experiment to obtain the value of the coupling constant.
The experiments supply accurate values of 13C and 15N chemical shifts and carbon–carbon and carbon–nitrogen coupling constants. These values can help to reveal structural features
of nucleic acids either directly or via induced changes when the sample is dissolved in oriented media.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
34.
35.
Daniela Guicking Brigitte Fiala Frank R. Blattner Ferry Slik Maryati Mohamed Kurt Weising 《Tree Genetics & Genomes》2011,7(3):573-585
Macaranga (Euphorbiaceae) has received much ecological and evolutionary research attention as a genus that includes some of the most
conspicuous pioneer trees of Southeast Asian tropical rainforests and because of its manifold associations with ants, including
about 30 species that are obligate ant-plants (myrmecophytes). We used sequence data from three chloroplast DNA loci (ccmp5,
ccmp6, atpB-rbcL) to assess phylogeographical patterns in species of Macaranga, section Pruinosae, sampled from various regions of Borneo and the Malay Peninsula. Forty-nine chloroplast DNA haplotypes (HT) were identified
among 768 specimens from five species, Macaranga gigantea (N = 329; 23 HT), Macaranga pearsonii (N = 347; 21 HT), Macaranga puberula (N = 24; 4 HT), Macaranga hosei (N = 48; 6 HT), and Macaranga pruinosa (N = 20; 5 HT). Forty-one haplotypes were species-specific, whereas eight haplotypes were shared by two, three, or four species
and occupied internal positions in a parsimony network. Population genetic parameters based on haplotype frequencies proved
to be in a similar range in the non-myrmecophytic M. gigantea and in the ant-associated M. pearsonii, which have overlapping distributions in northern and eastern Borneo. A comparison of G
ST and N
ST values revealed a strong phylogeographic structure in both species, whereas colonization pathways suggested by the network
topology were different. Both species exhibited similar levels of haplotypic diversity and moderate to high levels of population
differentiation. There were no obvious indications for an influence of the symbiotic ant partners on the population structure
of their host plants. 相似文献
36.
Horničáková M Kohoutová J Schlagnitweit J Wohlschlager C Ettrich R Fiala R Schoefberger W Müller N 《Biomolecular NMR assignments》2011,5(2):169-175
PsbQ is one of the extrinsic proteins situated on the lumenal surface of photosystem II (PSII) in the higher plants and green
algae. Its three-dimensional structure was determined by X-ray crystallography with exception of the residues 14–33. To obtain
further details about its structure and potentially its dynamics, we approached the problem by NMR. In this paper we report
1H, 15N, and 13C NMR assignments for the PsbQ protein. The very challenging oligo-proline stretches could be assigned using 13C-detected NMR experiments that enabled the assignments of twelve out of the thirteen proline residues of PsbQ. The identification
of PsbQ secondary structure elements on the basis of our NMR data was accomplished with the programs TALOS+, web server CS23D
and CS-Rosetta. To obtain additional secondary structure information, three-bond HN-Hα J-coupling constants and deviation of experimental 13Cα and 13Cβ chemical shifts from random coil values were determined. The resulting “consensus” secondary structure of PsbQ compares very
well with the resolved regions of the published X-ray crystallographic structure and gives a first estimate of the structure
of the “missing link” (i.e. residues 14–33), which will serve as the basis for the further investigation of the structure,
dynamics and interactions. 相似文献
37.
Infectious diseases are contributing to the decline of endangered amphibians. We identified myxosporean parasites, Myxidium spp. (Myxosporea: Myxozoa), in the brain and liver of declining native frogs, the Green and Golden Bell frog (Litoria aurea) and the Southern Bell frog (Litoria raniformis). We unequivocally identified two Myxidium spp. (both generalist) affecting Australian native frogs and the invasive Cane toad (Bufo marinus, syn. Rhinella marina) and demonstrated their association with disease. Our study tested the identity of Myxidium spp. within native frogs and the invasive Cane toad (brought to Australia in 1935, via Hawaii) to resolve the question whether the Cane toad introduced them to Australia. We showed that the Australian brain and liver Myxidium spp. differed 9%, 7%, 34% and 37% at the small subunit rDNA, large subunit rDNA, internal transcribed spacers 1 and 2, but were distinct from Myxidium cf. immersum from Cane toads in Brazil. Plotting minimum within-group distance against maximum intra-group distance confirmed their independent evolutionary trajectory. Transmission electron microscopy revealed that the brain stages localize inside axons. Myxospores were morphologically indistinguishable, therefore genetic characterisation was necessary to recognise these cryptic species. It is unlikely that the Cane toad brought the myxosporean parasites to Australia, because the parasites were not found in 261 Hawaiian Cane toads. Instead, these data support the enemy-release hypothesis predicting that not all parasites are translocated with their hosts and suggest that the Cane toad may have played an important spill-back role in their emergence and facilitated their dissemination. This work emphasizes the importance of accurate species identification of pathogens relevant to wildlife management and disease control. In our case it is paving the road for the spill-back role of the Cane toad and the parasite emergence. 相似文献
38.
Sánchez-Soriano N Bottenberg W Fiala A Haessler U Kerassoviti A Knust E Löhr R Prokop A 《Developmental biology》2005,288(1):126-138
Dendrites represent arborising neurites in both vertebrates and invertebrates. However, in vertebrates, dendrites develop on neuronal cell bodies, whereas in higher invertebrates, they arise from very different neuronal structures, the primary neurites, which also form the axons. Is this anatomical difference paralleled by principal developmental and/or physiological differences? We address this question by focussing on one cellular model, motorneurons of Drosophila and characterise the compartmentalisation of these cells. We find that motorneuronal dendrites of Drosophila share with typical vertebrate dendrites that they lack presynaptic but harbour postsynaptic proteins, display calcium elevation upon excitation, have distinct cytoskeletal features, develop later than axons and are preceded by restricted localisation of Par6-complex proteins. Furthermore, we demonstrate in situ and culture that Drosophila dendrites can be shifted from the primary neurite to their soma, i.e. into vertebrate-like positions. Integrating these different lines of argumentation, we propose that dendrites in vertebrates and higher invertebrates have a common origin, and differences in dendrite location can be explained through translocation of neuronal cell bodies introduced during the evolutionary process by which arthropods and vertebrates diverged from a common urbilaterian ancestor. Implications of these findings for studies of dendrite development, neuronal polarity, transport and evolution are discussed. 相似文献
39.
Background
It has been argued that multibreed animal models should include a heterogeneous covariance structure. However, the estimation of the (co)variance components is not an easy task, because these parameters can not be factored out from the inverse of the additive genetic covariance matrix. An alternative model, based on the decomposition of the genetic covariance matrix by source of variability, provides a much simpler formulation. In this study, we formalize the equivalence between this alternative model and the one derived from the quantitative genetic theory. Further, we extend the model to include maternal effects and, in order to estimate the (co)variance components, we describe a hierarchical Bayes implementation. Finally, we implement the model to weaning weight data from an Angus × Hereford crossbred experiment.Methods
Our argument is based on redefining the vectors of breeding values by breed origin such that they do not include individuals with null contributions. Next, we define matrices that retrieve the null-row and the null-column pattern and, by means of appropriate algebraic operations, we demonstrate the equivalence. The extension to include maternal effects and the estimation of the (co)variance components through the hierarchical Bayes analysis are then straightforward. A FORTRAN 90 Gibbs sampler was specifically programmed and executed to estimate the (co)variance components of the Angus × Hereford population.Results
In general, genetic (co)variance components showed marginal posterior densities with a high degree of symmetry, except for the segregation components. Angus and Hereford breeds contributed with 50.26% and 41.73% of the total direct additive variance, and with 23.59% and 59.65% of the total maternal additive variance. In turn, the contribution of the segregation variance was not significant in either case, which suggests that the allelic frequencies in the two parental breeds were similar.Conclusion
The multibreed maternal animal model introduced in this study simplifies the problem of estimating (co)variance components in the framework of a hierarchical Bayes analysis. Using this approach, we obtained for the first time estimates of the full set of genetic (co)variance components. It would be interesting to assess the performance of the procedure with field data, especially when interbreed information is limited. 相似文献40.
Borská L Fiala Z Krejsek J Andrýs C Vokurková D Hamáková K Kremlácek J Ettler K 《Physiological research / Academia Scientiarum Bohemoslovaca》2006,55(6):699-706
Psoriasis is one of the most frequent inflammatory skin diseases in which abnormal individual immune reactivity plays an important role. The aim of the present study was to describe selected immunological changes, concerning pro-inflammatory cytokines (TNF-alpha, IL-8) and adhesion molecules (sE-selectin, sP-selectin, sICAM-1), in 56 patients cured by Goeckerman's therapy (GT). GT includes dermal application of crude coal tar (containing polycyclic aromatic hydrocarbons) and exposure to UV radiation. When compared with the control group (healthy blood donors), the patients before GT had significantly increased serum levels of sE-selectin (p<0.001), sP-selectin (p<0.001), sICAM-1 (p<0.001) and IL-8 (p<0.001). Significantly decreased serum levels of sE-selectin (p<0.05) and significantly increased serum levels of IL-8 (p<0.05) were found after GT therapy. Serum levels of sICAM significantly correlated with the disease activity and with serum levels of sE-selectin. The level of PASI score (Psoriasis Area and Severity Index) significantly decreased after GT (p<0.001) and confirms the high efficiency GT. These findings confirmed that pro-inflammatory chemokine (IL-8) and adhesion molecules (sE-selectin, sP-selectin, sICAM-1) play an important role in the development and regulation of inflammation in psoriasis. Determination of sE-selectin and sICAM seems to be a promising marker of psoriasis's activity. Chemokine pathway (IL-8) and TNF-alpha activity seem to be modulated by Goeckerman's therapy (polycyclic aromatic hydrocarbons). 相似文献