Habitat-mediated, density-dependent dispersal strategies affecting spatial dynamics of populations in an anthropogenically-modified landscape.

A major challenge in managing natural populations in ecosystems is understanding and predicting the complexity and consequences of population dispersal. Although many studies have documented the importance of conspecific density and habitat quality in the dispersal process, we lack an understanding of how to integrate these factors in determining the spatial dynamics of populations or how habitat quality can mediate density-dependent dispersal. In this study, we propose a Habitat-mediated, Density-dependent, Spatial Population Dynamics model (HD-SPDM), in which we combined a Habitat Suitability Index (HSI) with a migration function, to explore the emergent effects of habitat mediated, density-dependent dispersal strategies on the spatial dynamics of a population. Our results show that habitat condition (based on HSI score) can influence ranges in conspecific density (which in turn can alter spatial patterns of populations distributed in homogeneous patches). We tested this model using the spatial distribution of Chinese mitten crab in the Yangtze River Estuary, which has been subjected to excessive sea reclamations over time, this allowed us to obtain insight into spatial distribution of population by determining how habitat-mediated, density-dependent dispersal at a small scale interacts with habitat heterogeneity and fragmentation at a landscape scale. We found that each progressive sea reclamation reduced suitable habitat area and habitat connectivity in the estuary. However, the model predicts that intermediate intensities of habitat compression and fragmentation could improve habitat utilization somewhat by facilitating population dispersal. Our model could be used to improve resource management of populations being increasingly impacted by anthropogenic alterations.