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Large herbivorous mammals act as vectors of dispersal for many forbs and grasses through ingestion and excretion of seeds (endozoochory). Attributes from the plant, animal and landscape need to be integrated in order to study patterns of dispersal in the field, for instance, with respect to the spatial deposition of single plant species in heterogeneous landscapes (‘seed shadows’). Drawing on a set of empirical data, we investigated the dispersal of 25 plant species by cattle in a coastal dune area by means of a spatially explicit simulation model. Model output for the number of dispersed seeds matched observations from field-collected dung pats well. We then applied the model to quantify the seed shadow among the landscape's main vegetation types, focusing on whether the transfer of plants is directed towards suitable habitat. We herewith examined how changing habitat availability in the face of vegetation succession and management affects deposition patterns. A simple wind dispersal model was included for comparison. Simulation showed endozoochorous deposition to be most likely in grassland, but not when this habitat's surface area was low. Since the probability to end up in grassland was higher than expected from random dispersal, grassland plants were always provided with directed dispersal (but not always as strong). Our model illustrates the potential of grazers to contribute in directed seed transfer, apart from their role in long-distance dispersal. [Copyright &y& Elsevier]

Different species have different dispersal capabilities and in the field, species interact with each other within dynamic, heterogeneous and complex landscapes. While plants and certain herbivore species may disperse considerable distances by means of seed dispersal or flight, other herbivores (e.g. root-feeding nematodes or non-winged insect herbivores) are more limited in their dispersal capacities. This difference in dispersal capabilities results in mosaics of plant-herbivore interactions that shift over time and space leading to spatio-temporal variation in both the presence and absence of the species and their interactions. We developed an individual based simulation model in which we examined how multi-species interactions are affected by their mobility within structurally complex landscapes. The main objective was to address the consequences for the arms race between plant defence and herbivore resistance to changes in fundamental landscape and community attributes. We demonstrate that feedbacks between landscape structure, community structure and the specific dispersal rate of the species involved affect the evolutionary dynamics between plants and herbivore antagonists. While three-species interactions result in increased plant defence and herbivore resistance, effects of dispersal have diverse effects depending on the prevailing landscape structure. [ABSTRACT FROM AUTHOR]

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