scholarly journals An integro-PDE model for evolution of random dispersal

2017 ◽  
Vol 272 (5) ◽  
pp. 1755-1790 ◽  
Author(s):  
King-Yeung Lam ◽  
Yuan Lou
Keyword(s):  
Pde Model ◽  
Random Dispersal

scholarly journals Community structure and carbonate production of a temperate rhodolith bank from Arvoredo Island, southern Brazil

2004 ◽  
Vol 52 (3-4) ◽  
pp. 207-224 ◽  
Author(s):  
Douglas F. M. Gherardi
Keyword(s):  
Community Structure ◽  
Coralline Algae ◽  
Carbonate Content ◽  
Production Rates ◽  
Percentage Cover ◽  
Coralline Red Algae ◽  
Carbonate Production ◽  
Random Dispersal ◽  
Long Run ◽  
Main Bank

A small (100,000 m²) rhodolith bank located at the Arvoredo Marine Biological Reserve (Santa Catarina, Brazil) has been surveyed to determine the main bank components, the community structure, and carbonate production rates. Data from five photographic transects perpendicular to Arvoredo Island shore were complemented with sediment samples and shallow cores, all collected by scuba diving. The main bank component is the unattached, nongeniculate, coralline red algae Lithophyllum sp., used as substrate by the zoanthid Zoanthus sp. Percentage cover of living and dead coralline algae, zoanthids and sediment patches account for nearly 98% of the investigated area. Classification and ordination of samples showed that differences in the proportion of live and dead thalli of Lithophyllum sp. determine the relative abundances of zoanthids. Results also indicate that similarity of samples is high and community gradients are subtle. Significant differences in percentage cover along transects are concentrated in the central portion of the bank. Low carbonate content of sediments from deeper samples suggests low rates of recruitment and dispersal of coralline algae via fragmentation. However, carbonate production of Lithophyllum sp ranging from 55-136.3 g m-2 yr-1 agrees with production rates reported for other temperate settings. In the long run, rhodolith density at Arvoredo Is. is likely to be dependent upon random dispersal of spores and/or fragments from other source areas.

Comparison of Two Models for Prediction of Seismic Streamer State Using the Ensemble Kalman Filter

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Jan Vidar Grindheim ◽  
Inge Revhaug ◽  
Egil Pedersen ◽  
Peder Solheim
Keyword(s):  
Kalman Filter ◽  
Ensemble Kalman Filter ◽  
Petroleum Exploration ◽  
Drift Angle ◽  
Pde Model ◽  
Survey Line ◽  
Position Data ◽  
Position Prediction ◽  
Increasing Demand ◽  
Marine Seismic

Towed marine seismic streamers are extensively utilized for petroleum exploration. With the increasing demand for efficiency, leading to longer and more densely spaced streamers, as well as four-dimensional (4D) surveys and more complicated survey configurations, the demand for optimal streamer steering has increased significantly. Accurate streamer state prediction is one important aspect of efficient streamer steering. In the present study, the ensemble Kalman filter (EnKF) has been used with two different models for data assimilation including parameter estimation followed by position prediction. The data used are processed position data for a seismic streamer at the very start of a survey line with particularly large cable movements due to currents. The first model is a partial differential equation (PDE) model reduced to two-dimensional (2D), solved using a finite difference method (FDM). The second model is based on a path-in-the-water (PIW) model and includes a drift angle. Prediction results using various settings are presented for both models. A variant of the PIW method gives the overall best results for the present data.

PDE Model with External Transfer

2020 ◽  
pp. 49-70
Author(s):  
William E. Schiesser
Keyword(s):  
Pde Model

scholarly journals Habitat choice meets thermal specialization: Competition with specialists may drive suboptimal habitat preferences in generalists

2018 ◽  
Vol 115 (47) ◽  
pp. 11988-11993 ◽  
Author(s):  
Staffan Jacob ◽  
Estelle Laurent ◽  
Bart Haegeman ◽  
Romain Bertrand ◽  
Jérôme G. Prunier ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Environmental Variability ◽  
Habitat Preferences ◽  
Habitat Choice ◽  
Current Theory ◽  
Ecological Specialization ◽  
Metapopulation Model ◽  
Niche Specialization ◽  
Random Dispersal ◽  
Limited Dispersal

Limited dispersal is classically considered as a prerequisite for ecological specialization to evolve, such that generalists are expected to show greater dispersal propensity compared with specialists. However, when individuals choose habitats that maximize their performance instead of dispersing randomly, theory predicts dispersal with habitat choice to evolve in specialists, while generalists should disperse more randomly. We tested whether habitat choice is associated with thermal niche specialization using microcosms of the ciliate Tetrahymena thermophila, a species that performs active dispersal. We found that thermal specialists preferred optimal habitats as predicted by theory, a link that should make specialists more likely to track suitable conditions under environmental changes than expected under the random dispersal assumption. Surprisingly, generalists also performed habitat choice but with a preference for suboptimal habitats. Since this result challenges current theory, we developed a metapopulation model to understand under which circumstances such a preference for suboptimal habitats should evolve. We showed that competition between generalists and specialists may favor a preference for niche margins in generalists under environmental variability. Our results demonstrate that the behavioral dimension of dispersal—here, habitat choice—fundamentally alters our predictions of how dispersal evolve with niche specialization, making dispersal behaviors crucial for ecological forecasting facing environmental changes.

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