Richard S. Ostfeld, Charles D. Canham, Felicia Keesing
This research will link two key ecological processes that until now have been treated as conceptually distinct phenomena: dispersal dynamics of mobile animals in a patchy landscape, and the effects of seed consumers on tree regeneration in forested landscapes. The primary goals are to (1) determine whether populations of white-footed mice (Peromyscus leucopus) demonstrate source-sink dynamics in the patchy, postagricultural landscapes of northeastern U.S. and (2) reveal the consequences of dispersal patterns by mice (whether source-sink or an alternative model) for the survival of tree seeds and ultimately for forest regeneration. This will allow for linkage of animal dispersal dynamics with community dynamics of plants. Three landscape patch types will be studied: oak-dominated forests, maple-dominated forests, and shrub- and herb-dominated oldfields. All three patch types are connected to one another along extensive, sharp edges, and mice occupy all three patch types. It is hypothesized that oak patches support source populations in post-acorn-mast years, during which maple and oldfield patches are sinks and the PIs will: (1) measure the net direction of dispersal between patch types; (2) estimate the mean fitness within populations in each patch type, using direct measurements of mortality and natality; and (3) enclose populations and follow growth trajectories in the patch type (oldfield). Together, these approaches will distinguish source-sink dynamics from alternative models.
