Spatial patterns of seed dispersal and the unification of plant population ecology

Seed dispersal determines the conditions that seeds, seedlings, and saplings confront, and thus potentially provides a unifying theme for plant population ecology. This potential is seldom realized, however, because dispersal is infrequently linked effectively with its consequences. We advocate the importance of explicitly designing studies quantifying spatial patterns of dispersal at a variety of scales, causes of those spatial patterns, and consequences of alternative patterns of dispersal for all stages from seed to new adult. It is critical to link this chain of events with thorough investigations of individual dispersal systems rather than continuing to collect small pieces of the story from a multitude of systems. We first present a brief overview of spatial patterns, causes, and consequences of dispersal. We then develop the argument that a correspondence, or lack of correspondence, between patterns of seed arrival and adult recruitment tells little about causal relationships between the two. Finally, we suggest that a combination of observational and experimental approaches taking into account the complexities of recruitment processes will better link dispersal with its consequences. Experimental manipulations of patterns of seed arrival and causal modelling are potentially powerful approaches, but may be limited in application to easily manageable species.