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1.
There is accumulating evidence that individuals leave their natal area and select a breeding habitat non-randomly by relying upon information about their natal and future breeding environments. This variation in dispersal is not only based on external information (condition dependence) but also depends upon the internal state of individuals (phenotype dependence). As a consequence, not all dispersers are of the same quality or search for the same habitats. In addition, the individual's state is characterized by morphological, physiological or behavioural attributes that might themselves serve as a cue altering the habitat choice of conspecifics. These combined effects of internal and external information have the potential to generate complex movement patterns and could influence population dynamics and colonization processes. Here, we highlight three particular processes that link condition-dependent dispersal, phenotype-dependent dispersal and habitat choice strategies: (1) the relationship between the cause of departure and the dispersers' phenotype; (2) the relationship between the cause of departure and the settlement behaviour and (3) the concept of informed dispersal, where individuals gather and transfer information before and during their movements through the landscape. We review the empirical evidence for these processes with a special emphasis on vertebrate and arthropod model systems, and present case studies that have quantified the impacts of these processes on spatially structured population dynamics. We also discuss recent literature providing strong evidence that individual variation in dispersal has an important impact on both reinforcement and colonization success and therefore must be taken into account when predicting ecological responses to global warming and habitat fragmentation.  相似文献   
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Di Jin  Porter Hoagland   《Harmful algae》2008,7(6):772-781
In this study, we develop a framework for measuring the value of harmful algal bloom (HAB) predictions. The framework captures the effects of both private and public responses to HABs. Using data from the New England nearshore commercial shellfish fishery and impact estimates for a large-scale HAB event in 2005, we illustrate how the potential value of HAB forecasts may be estimated. The results of our study suggest that the long-term value of a HAB prediction and tracking system for the Gulf of Maine is sensitive to the frequency of HAB events, the accuracy of predictions, the choice of HAB impact measures, and the effectiveness of public and private responses.  相似文献   
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In the Northern Hemisphere, the surface of south-facing slopes orients toward the sun and thus receives a greater duration and intensity of solar irradiation, resulting in a relatively warmer, drier microclimate and seasonal environmental extremes. This creates potentially detrimental conditions for evergreen plants which must endure the full gamut of conditions. I hypothesize that (1) increased southerly aspect will correlate negatively with evergreen understory plant distributions; (2) derived environmental variables (summer and winter light and heat load) will predict variance in evergreen distributions as well as topographic position (aspect, slope, and elevation) and (3) winter light will best predict evergreen understory plant distributions. In order to test these hypotheses, survey data were collected characterizing 10 evergreen understory herb distributions (presence, abundance, and reproduction) as well as the corresponding topographical information across north- and south-facing slopes in the North Carolina mountains and Georgia piedmont. The best predictive models were selected using AIC, and Bayesian hierarchical generalized linear models were used to estimate the strength of the retained coefficients. As predicted, evergreen understory herbs occurred and reproduced less on south-facing than north-facing slopes, though slope and elevation also had robust predictive power, and both discriminated well between evergreen species. While the landscape variables explained where the plants occurred, winter light and heat load provided the best explanation why they were there. Evergreen plants likely are limited on south-facing slopes by low soil moisture combined with high temperatures in summer and high irradiance combined with lower temperatures in winter. The robust negative response of the understory evergreen herbs to increased winter light also suggested that the winter rather than the summer (or growing season) environment provided the best predictive power for understory evergreen distributions, which has substantive implications for predicting responses to global climate change.  相似文献   
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The concept of positional information is central to our understanding of how cells determine their location in a multicellular structure and thereby their developmental fates. Nevertheless, positional information has neither been defined mathematically nor quantified in a principled way. Here we provide an information-theoretic definition in the context of developmental gene expression patterns and examine the features of expression patterns that affect positional information quantitatively. We connect positional information with the concept of positional error and develop tools to directly measure information and error from experimental data. We illustrate our framework for the case of gap gene expression patterns in the early Drosophila embryo and show how information that is distributed among only four genes is sufficient to determine developmental fates with nearly single-cell resolution. Our approach can be generalized to a variety of different model systems; procedures and examples are discussed in detail.  相似文献   
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This study evaluated whether showing a video of the different ways of raising goats for milk affected consumer acceptability. Four combinations, 2 Videos (intensive [INT] and semiextensive [SEM] system) × 2 Milk Types (semiskimmed [S] and whole [W] milk), were evaluated by 70 habitual consumers of goat milk, who scored their liking and purchase intention during blind (B), expected (E), and informed (I) acceptability sessions. In the B session, consumers tasted both milk types without information. S samples were preferred over W samples. In the E session, SEM video created high expectations in terms of milk liking and purchase intent, whereas the opposite happened when showing INT video. In the I session, consumers showed a clear preference for combinations created using SEM video, regardless of milk type. W-SEM and S-INT were worse (negative disconfirmation) and better (positive disconfirmation) than expected, respectively. A complete assimilation toward expectations occurred only for S-INT. INT video adversely affected the acceptability of S samples. Concerning purchase intent, W-SEM and S-SEM were worse than expected, but the assimilation was complete only for S-SEM: SEM video increased purchase intent for S samples.  相似文献   
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Butana and Kenana breeds from Sudan are part of the East African zebu Bos indicus type of cattle. Unlike other indigenous zebu cattle in Africa, they are unique due to their reputation for high milk production and are regarded as dairy cattle, the only ones of their kind on the African continent. In this study, we sequenced the complete mitochondrial DNA (mtDNA) D‐loop of 70 animals to understand the maternal genetic variation, demographic profiles and history of the two breeds in relation to the history of cattle pastoralism on the African continent. Only taurine mtDNA sequences were identified. We found very high mtDNA diversity but low level of maternal genetic structure within and between the two breeds. Bayesian coalescent‐based analysis revealed different historical and demographic profiles for the two breeds, with an earlier population expansion in the Butana vis a vis the Kenana. The maternal ancestral populations of the two breeds may have diverged prior to their introduction into the African continent, with first the arrival of the ancestral Butana population. We also reveal distinct demographic history between the two breeds with the Butana showing a decline in its effective population size (Ne) in the recent past ~590 years. Our results provide new insights on the early history of cattle pastoralism in Sudan indicative of a large ancient effective population size.  相似文献   
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Genetic diversity provides the raw material for populations to respond to changing environmental conditions. The evolution of diversity within populations is based on the accumulation of mutations and their retention or loss through selection and genetic drift, while migration can also introduce new variation. However, the extent to which population growth and sustained large population size can lead to rapid and significant increases in diversity has not been widely investigated. Here, we assess this empirically by applying approximate Bayesian computation to a novel ancient DNA dataset that spans the life of a southern elephant seal (Mirounga leonina) population, from initial founding approximately 7000 years ago to eventual extinction within the past millennium. We find that rapid population growth and sustained large population size can explain substantial increases in population genetic diversity over a period of several hundred generations, subsequently lost when the population went to extinction. Results suggest that the impact of diversity introduced through migration was relatively minor. We thus demonstrate, by examining genetic diversity across the life of a population, that environmental change could generate the raw material for adaptive evolution over a very short evolutionary time scale through rapid establishment of a large, stable population.  相似文献   
10.
Summary Triple-resonance experiments can be designed to provide useful information on spin-system topologies. In this paper we demonstrate optimized proton and carbon versions of PFG-CT-HACANH and PFG-CT-HACA(CO)NH straight-through triple-resonance experiments that allow rapid and almost complete assignments of backbone H, 13C, 15N and HN resonances in small proteins. This work provides a practical guide to using these experiments for determining resonance assignments in proteins, and for identifying both intraresidue and sequential connections involving glycine residues. Two types of delay tunings within these pulse sequences provide phase discrimination of backbone Gly C and H resonances: (i) C–H phase discrimination by tuning of the refocusing period a_f; (ii) C–C phase discrimination by tuning of the 13C constant-time evolution period 2Tc. For small proteins, C–C phase tuning provides better S/N ratios in PFG-CT-HACANH experiments while C–H phase tuning provides better S/N ratios in PFG-CT-HACA(CO)NH. These same principles can also be applied to triple-resonance experiments utilizing 13C-13C COSY and TOCSY transfer from peripheral side-chain atoms with detection of backbone amide protons for classification of side-chain spin-system topologies. Such data are valuable in algorithms for automated analysis of resonance assignments in proteins.  相似文献   
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