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101.
Many factors contribute to the success of a socially parasitic strategy, especially the ability of the parasite to invade
a host colony. However, little research has focused on the choices that may be made by an invading parasite, specifically
whether parasites actively discriminate between different host colonies and if they have a preference for colonies of a particular
size. When an allodapine social parasite, Inquilina schwarzi, was presented with colonies of their host species, Exoneura robusta, the parasites were found to invade the larger host colonies. However, it could not be ascertained from this study whether
the parasites were making an active decision concerning which colony to invade, or whether they were simply more attracted
to the larger colonies due to potentially stronger odour cues. Regardless of the cause, the larger host colonies are more
at risk of being invaded by a social parasite, which would give parasites greater resources for exploitation and could also
provide selection against the large host colony sizes. 相似文献
102.
Fabien Corblin Sbastien Tripodi Eric Fanchon Delphine Ropers Laurent Trilling 《Bio Systems》2009,98(2):91-104
Dynamical modeling has proven useful for understanding how complex biological processes emerge from the many components and interactions composing genetic regulatory networks (GRNs). However, the development of models is hampered by large uncertainties in both the network structure and parameter values. To remedy this problem, the models are usually developed through an iterative process based on numerous simulations, confronting model predictions with experimental data and refining the model structure and/or parameter values to repair the inconsistencies. In this paper, we propose an alternative to this generate-and-test approach. We present a four-step method for the systematic construction and analysis of discrete models of GRNs by means of a declarative approach. Instead of instantiating the models as in classical modeling approaches, the biological knowledge on the network structure and its dynamics is formulated in the form of constraints. The compatibility of the network structure with the constraints is queried and in case of inconsistencies, some constraints are relaxed. Common properties of the consistent models are then analyzed by means of dedicated languages. Two such languages are introduced in the paper. Removing questionable constraints or adding interesting ones allows to further analyze the models. This approach allows to identify the best experiments to be carried out, in order to discriminate sets of consistent models and refine our knowledge on the system functioning. We test the feasibility of our approach, by applying it to the re-examination of a model describing the nutritional stress response in the bacterium Escherichia coli. 相似文献
103.
The invertebrate fauna of the nests of three seabird species, black-legged kittiwakes (Rissa tridactyla), common eider (Somateria mollissima) and glaucous gull (Larus hyperboreus), were sampled in Kongsfjorden, Spitsbergen, Svalbard. The invertebrate community was species poor, consisting predominantly
of the flea, Mioctenopsylla arctica arctica (Insecta: Siphonaptera), but with six species of oribatid mite (Acari: Oribatida), Diapterobates notatus, Oribatula tibialis, Ameronothrus lineatus, Hermannia reticulata, Trichoribates trimaculatus and Ceratoppia bipilis, plus an occasional mesostigmatid mite. No Collembola or ticks (Acari: Ixodidae) were observed. With the exception of M. arctica arctica, the fauna of seabird nests consisted of opportunistic microarthropod species rather than specialised nest-dwelling or bird
parasitic species. Species diversity of soil oribatid mites was greater in nests of the common eider than compared to nests
of the black-legged kittiwake, which may be related to the ground nesting behaviour of the common eiders. No rare or unusual
microarthropod species for Svalbard were found in the seabird nests. The contentions that nests may facilitate microarthropod
colonisation of High Arctic regions via bird phoresy by providing a high-quality habitat at the point of arrival, or that
there might be a specialised microarthropod fauna exploiting this habitat, were not supported in this study. These are amongst
the first data on the microarthropod community of seabird nests in the High Arctic. 相似文献
104.
Three factors and their interaction effects are increasingly recognized as important determinants of nest predation: nest
concealment, nest height, and predator type. The risk of nest predation is predicted to vary across these variables because
of nest detectability and accessibility. In general, however, few studies examine how these three variables interact in relation
to nest predation, focusing instead on either nest concealment or nest height (whereby predator identity is usually not known).
In this study, we examine the role of nest concealment and nest height for nest survival using both artificial and natural
nests in the superb fairy-wren (Malurus cyaneus). We indirectly identified potential predators through marks left on artificial eggs and footprints left on tracking tunnels.
Predation level at artificial nests was lower than at natural nests, and this could be due to a failure of some nest predators
to locate cryptic nests in the absence of cues provided by parental activity. Our results supported the prediction that exposed
and concealed nests have different levels of nest predation, which can be explained by variation in predator type. Visual
predators were only detected at exposed nests, and survival from visual predators was lower for high nests that were also
exposed. However, olfactory predators were detected irrespective of nest height or nest concealment. Because rodents use olfaction
to locate nests, this could explain the lack of association between nest concealment and predation outcome at low nests. In
addition, rodent footmarks near nests were significantly associated with rodent tooth marks on eggs. 相似文献
105.
M.A. Andersson R. Mikkola M. Raulio L. Kredics P. Maijala M.S. Salkinoja-Salonen 《Journal of applied microbiology》2009,106(3):909-923
Aims: To identify a toxin and its producer isolated from woody material in a building where the occupants experienced serious ill health symptoms.
Methods and Results: Hyphal extracts of an indoor fungus, identified as the cycloheximide-tolerant species Acremonium exuviarum , inhibited motility of boar spermatozoa (EC50 5 ± 2 μg of crude solids ml−1 ) and caused cytolysis of murine neuroblastoma cells (MNA) and feline fetal lung cells (FL). The responsible substances were purified and identified as two structurally similar, heat-stable, novel, toxic peptaibols, 1726 Da and 1740 Da, respectively, with amino acid sequences of Acetyl-Phe-Iva/Val-Gln-Aib-Ile-Thr-Leu-Aib-Pro-Aib-Gln-Pro-Aib-(X-X-X)-SerOH and Acetyl-Phe-Iva/Val-Gln-Aib-Ile-Thr-Leu-Val-Pro-Aib-Gln-Pro-Aib-(X-X-X)-SerOH. Purified acrebol inhibited motility of boar sperm, depleted ATP half-content in 1 day (EC50 of 0·1 μg ml−1 , 60 nmol l−1 ) depolarised the mitochondria after 2 days, but did not affect the cellular content in NADH. This indicates mitochondrial toxicity. Plate-grown biomass of A. exuviarum BMB4 contained 0·1–1% (w/w) of acrebol, depending on the culture medium.
Conclusions: Acrebol paralysed the energy generation of mammalian cells suggesting that mitochondria were its target of action.
Significance and Impact of the Study: Acremonium exuviarum, as an indoor fungus, is potentially hazardous to health because of the toxic peptaibols that it produces. 相似文献
Methods and Results: Hyphal extracts of an indoor fungus, identified as the cycloheximide-tolerant species Acremonium exuviarum , inhibited motility of boar spermatozoa (EC
Conclusions: Acrebol paralysed the energy generation of mammalian cells suggesting that mitochondria were its target of action.
Significance and Impact of the Study: Acremonium exuviarum, as an indoor fungus, is potentially hazardous to health because of the toxic peptaibols that it produces. 相似文献
106.
Paul A. Murtaugh 《Ecology letters》2009,12(10):1061-1068
I evaluated the predictive ability of statistical models obtained by applying seven methods of variable selection to 12 ecological and environmental data sets. Cross-validation, involving repeated splits of each data set into training and validation subsets, was used to obtain honest estimates of predictive ability that could be fairly compared among methods. There was surprisingly little difference in predictive ability among five methods based on multiple linear regression. Stepwise methods performed similarly to exhaustive algorithms for subset selection, and the choice of criterion for comparing models (Akaike's information criterion, Schwarz's Bayesian information criterion or F statistics) had little effect on predictive ability. For most of the data sets, two methods based on regression trees yielded models with substantially lower predictive ability. I argue that there is no 'best' method of variable selection and that any of the regression-based approaches discussed here is capable of yielding useful predictive models. 相似文献
107.
Urban areas are home to more than half of the world's people, responsible for >70% of anthropogenic release of carbon dioxide and 76% of wood used for industrial purposes. By 2050 the proportion of the urban population is expected to increase to 70% worldwide. Despite fast rates of change and potential value for mitigation of carbon dioxide emissions, the organic carbon storage in human settlements has not been well quantified. Here, we show that human settlements can store as much carbon per unit area (23–42 kg C m−2 urban areas and 7–16 kg C m−2 exurban areas) as tropical forests, which have the highest carbon density of natural ecosystems (4–25 kg C m−2 ). By the year 2000 carbon storage attributed to human settlements of the conterminous United States was 18 Pg of carbon or 10% of its total land carbon storage. Sixty-four percent of this carbon was attributed to soil, 20% to vegetation, 11% to landfills, and 5% to buildings. To offset rising urban emissions of carbon, regional and national governments should consider how to protect or even to increase carbon storage of human-dominated landscapes. Rigorous studies addressing carbon budgets of human settlements and vulnerability of their carbon storage are needed. 相似文献
108.
Sturgeon populations in the Danube River have been affected by a combination of hydropower development, over-harvesting, habitat
degradation from agricultural and industrial practices and from urbanization. The effects of these changes have been monitored
on six sturgeon species inhabiting the Danube River. Two of them are resident species, while the other four migrate to the
river for spawning. Atlantic sturgeon (Acipenser sturio) has completely disappeared from this region. Ship sturgeon (Acipenser nudiventris) is very rare in professional fishing catches. Beluga (Huso huso), Russian sturgeon (Acipenser gueldenstaedtii), stellate sturgeon (Acipenser stellatus) and sterlet (Acipenser ruthenus) are endangered with different levels of extinction risk. Here, we model the time dependence of the beluga and Russian sturgeon
catch in the Serbian part of the Danube River. Predicted extinction of Russian sturgeon was estimated to fall around the middle
of the century, and for beluga approximately at middle of the millennium. Suggestions for sturgeon conservation measures on
a national level and coordination of all relevant institutions in Serbia are also presented. 相似文献
109.
Kubrycht J Sigler K Růzicka M Soucek P Borecký J Jezek P 《Journal of molecular evolution》2006,63(5):691-706
Many structures and molecules closely related to those involved in the specific process of immunoglobulin (Ig) hypermutation existed before the appearance of primordial Ig genes. Consequently, these structures can be found even in animals and organisms distinct from vertebrates; likewise, homologues of hypermutation enzymes are present in a broad range of species, from bacteria to mammals. Our analysis, based predominantly on primary structure, demonstrates the existence of molecules similar to Ig domains, variable Ig domains (IGv), and antigen receptors (AR) in unicellular organisms, nonvertebrate metazoans, and nonvertebrate Coelomata, respectively. In addition, we deal here with some important structural properties of CDR1-like segments of the selected sponge adhesion molecule GCSAMS exhibiting chimerical Ig domain similarities, and demonstrate the occurrence of conserved regions corresponding to Ohno's modern intact primordial building block in the C-terminal part of IGv-related segments of nonvertebrate origin. The results of our analysis are also discussed with respect to the possible phylogeny of molecules preceding the hypothetical common antigen receptor ancestor. 相似文献
110.