Directed drift selected different movement strategy in heterogeneous habitats

Habitat fragmentation is a significant threat to biodiversity because splitting habitats apart can prevent some species from accessing multiple patches across the landscape. Biologists have long debated the role that stochastic processes, environmental disturbances, and advection play in structuring the diversity and composition of species in fragmented environments. Locomotion is another driving factor in which species can adapt differently to fragmented environments contingent to the direction of advection, e.g., advection could be beneficial in allowing immobile species access to distant patches or detrimental as a way of preventing mobile species from accessing resources. However, such predictions have not been tested due to the limited amount of fieldwork available. Hence, more empirical work is needed to identify the role of dispersal on species responses to fragmentation along different directions of advection, to ultimately develop a more realistic movement ecology theory. In this study, we combined mathematical modeling and laboratory experiments to study how advection can affect species with different dispersal rates within fragmented environments. Our theoretical and empirical results showed consistently that fast dispersers were more affected by advection than slow dispersers, especially when the environment was extremely fragmented. Additionally, high dispersers showed larger changes among different habitat configurations, with the optimal environment being when the resources were spread apart moderately, which highlights the potential for heterogeneous habitats to offer refuge locations for fast moving individuals when they were able to reach the unaffected patches. Our findings shed new light on how external forces can affect how species perform in fragmented environments.