Random dispersal in theoretical populations

108

143

Invasive species are regularly claimed as the second threat to biodiversity. To apply a relevant response to the potential consequences associated with invasions (e.g., emphasize management efforts to prevent new colonization or to eradicate the species in places where it has already settled), it is essential to understand invasion mechanisms and dynamics. Quantifying and understanding what influences rates of spatial spread is a key research area for invasion theory. In this paper, we develop a model to account for occupancy dynamics of an invasive species. Our model extends existing models to accommodate several elements of invasive processes; we chose the framework of hierarchical modeling to assess site occupancy status during an invasion. First, we explicitly accounted for spatial structure and how distance among sites and position relative to one another affect the invasion spread. In particular, we accounted for the possibility of directional propagation and provided a way of estimating the direction of this possible spread. Second, we considered the influence of local density on site occupancy. Third, we decided to split the colonization process into two subprocesses, initial colonization and recolonization, which may be ground-breaking because these subprocesses may exhibit different relationships with environmental variations (such as density variation) or colonization history (e.g., initial colonization might facilitate further colonization events). Finally, our model incorporates imperfection in detection, which might be a source of substantial bias in estimating population parameters. We focused on the case of the Eurasian Collared-Dove (Streptopelia decaocto) and its invasion of the United States since its introduction in the early 1980s, using data from the North American BBS (Breeding Bird Survey). The Eurasian Collared-Dove is one of the most successful invasive species, at least among terrestrial vertebrates. Our model provided estimation of the spread direction consistent with empirical observations. Site persistence probability exhibits a quadratic response to density. We also succeeded at detecting differences in the relationship between density and initial colonization vs. recolonization probabilities. We provide a map of sites that may be colonized in the future as an example of possible practical application of our work.

Section: Introductionmentioning

confidence: 99%

Hierarchical modeling of an invasive spread: the Eurasian Collared-Dove Streptopelia decaocto in the United States

Bled

Royle

Cam

2011

108

143

“…Landscape pattern is also likely to be important to invasion outcome. Skellam (1951) used diffusion theory to characterize spread from a single point within a homogeneous landscape. However, real landscapes are not homogeneous and the rate of diffusive spread, which was constant in Skellam's equations, varies depending on the amount and fragmentation of suitable habitat (Bergelson et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Landscape connectivity and seed dispersal characteristics inform the best management strategy for exotic plants

Minor

Gardner

2011

Exotic plant invasions have triggered environmental and economic problems throughout the world. Our ability to manage these invasions is hindered by the difficulty of predicting spread in fragmented landscapes. Because the spatial pattern of invasions depends on the dispersal characteristics of the invasive species and the configuration of suitable habitat within the landscape, a universal management strategy is unlikely to succeed for any particular species. We suggest that the most effective management strategy may be an adaptive one that shifts from local control to landscape management depending on the specific invader and landscape. In particular, we addressed the question of where management activities should be focused to minimize spread of the invading species. By simulating an invasion across a real landscape (Antietam National Battlefield in Maryland, USA), we examined the importance of patch size and connectivity to management success. We found that the best management strategy depended on the dispersal characteristics of the exotic species. Species with a high probability of random long-distance dispersal were best managed by focusing on the largest patches, while species with a lower probability of random long-distance dispersal were best managed by considering landscape configuration and connectivity of the patches. Connectivity metrics from network analysis were useful for identifying the most effective places to focus management efforts. These results provide insight into invasion patterns of various species and suggest a general rule for managers in National Parks and other places where invasive species are a concern.

“…Analytical models of species migration have successfully been used to predict rates of species spread (e.g., Lubina and Levin 1987, Reeves and Usher 1989, Andow et al 1990, Allen et al 1991, Marinissen and van den Bosch 1992, the simple diffusion model of Skellam (1951) progressively being refined to produce more sophisticated models. These latter models incorporate biologically meaningful parameters, the values of which may be obtained from the literature or by means of field investigations (e.g., van den Bosch et al 1990, Hengeveld 1994).…”

Section: Introductionmentioning

confidence: 99%

Impacts of Habitat Fragmentation and Patch Size upon Migration Rates

Huntley

2000

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecological Applications. Abstract. A spatially explicit model (MIGRATE) was used to investigate the effects of habitat loss and fragmentation on the ability of species to migrate in response to climate change. Illustrative simulations were run using parameters that represent the reproductive and dispersal characteristics of the wind-dispersed tree Tilia cordata (small-leaved lime). Hierarchically structured landscapes with different patch sizes and overall habitat suitability levels were generated at a 1-km resolution for a 200 X 800 km area. Simulated migration rates slowed markedly when habitat availability fell below -25% of the landscape area, especially in landscapes composed of fewer larger patches. The implication of these results for the management of landscapes for species conservation is discussed.