Landscape structure affects dispersal in the greater white-toothed shrew: inference between genetic and simulated ecological distances

Animal dispersal in a fragmented landscape depends on the complex interaction between landscape structure and animal behavior. To better understand how individuals disperse, it is important to explicitly represent the properties of organisms and the landscape in which they move. A common approach to modelling dispersal includes representing the landscape as a grid of equal sized cells and then simulating individual movement as a correlated random walk. This approach uses a priori scale of resolution, which limits the representation of all landscape features and how different dispersal abilities are modelled. We develop a vector-based landscape model coupled with an object-oriented model for animal dispersal. In this spatially explicit dispersal model, landscape features are defined based on their geographic and thematic properties and dispersal is modelled through consideration of an organism's behavior, movement rules and searching strategies (such as visual cues). We present the model's underlying concepts, its ability to adequately represent landscape features and provide simulation of dispersal according to different dispersal abilities. We demonstrate the potential of the model by simulating two virtual species in a real Swiss landscape. This illustrates the model's ability to simulate complex dispersal processes and provides information about dispersal such as colonization probability and spatial distribution of the organism's path

[Illustrations de Au Temps des grands voiliers.] / Georges Le Poitevin, dess. ; Jean Furet, aut. du texte

Comprend : [Fig. après le titre :] Figure de proue de "France I". [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [Photographie 1 après le titre :] La magnifique voilure d'un Cap-Hornier. [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [Photographie 2 après le titre :] A serrer le Grand Perroquet volant avant. [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [Photographie 3 après le titre :] A serrer la Misaine. [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [Photographie 4 après le titre :] A la cape. Un beau coup de roulis. [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [pl. en reg. p.51. Chapitre III : un bateau Cap-Hornier, le Prométhée.] Dans le pot au noir. [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [pl. en reg. p.75. Chapitre IV : sur le pont d'un navire au moment du passage du Cap-Horn.] La houle furieuse du Cap Horn déferle sur le pont d'un voilier. [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [pl. en reg. p.103. Chapitre V :] Le timonier. [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [pl. en reg. p.195. Chapitre XI :] Serrer les voiles sur les vergues pendant la tempête est une manoeuvre périlleuse... [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [Pl. en reg. p.237 : schémas explicantifs des diverses parties d'une voile et d'une vergue. Rose des vents.] [Cote : 8 ° V 64722 (1,I)/microfilm R 122007] ; [pl. en double page après p.238 : Le cap-Hornier Le Prométhée.] Prométhée (...). [Cote : 8 ° V 64722 (1,I)/microfilm R 122007]

Relaxation times in a bistable system with parametric, white noise: Theory and experiment

We consider the effects of external, multiplicative white noise on the relaxation time of a general representation of a bistable system from the points of view provided by two, quite different, theoretical approaches: the classical Stratonovich decoupling of correlations and the new method due to Jung and Risken. Experimental results, obtained from a bistable electronic circuit, are compared to the theoretical predictions. We show that the phenomenon of critical slowing down appears as a function of the noise parameters, thereby providing a correct characterization of a noise-induced transition.