Linking Seed Dispersal Patterns with Seedling Establishment

Dispersal is the first of a series of stages that affects the subsequent plant regeneration process (Figure 5), determining the spatial arrangement and, consequently, the population dynamics of most plant species. In the case of fleshy-fruited plants, the facilitation effect of nurse or shelter plants is in turn enhanced by the fact that most seeds are deposited under shrubs that act as feeding source and shelter for frugivores (the so-called perching effect). The effect of nurse plants seems to be crucial in many ecosystems because they ameliorate the negative effect of summer drought in seedling survival, at least when resources are limiting, as it occurs in arid ecosystems.

However, in most cases, the recruitment dynamics is usually very complex, being the seed template produced by seed dispersal subsequently modified by other regeneration stages (from seed dispersal to seedling establishment). This is because processes acting at different stages are usually independent and 'uncoupled', and promote subsequently seed-seedling conflicts. For example, the deposition of large amounts of seeds by frugivores in a given microhabitat may be subjected to intense post-dispersal seed predation and/or be unsuitable for emergence or recruitment of seedlings. Moreover, such uncoupling among regeneration stages may be also variable across spatial and temporal scales and an increase of

Figure 5 Diagram representing the different stages (in circles) and processes (in squares) affecting them along the plant regeneration cycle. The overall probability of recruitment is obtained from the product of the partial probabilities of recruitment of each stage.

variability in a given stage may produce spatiotemporal mosaics through the plant regeneration process. Still, another possible source of conflict in the plant regeneration process is seed size. In general, larger seeds tend to have a higher chance of seedling emergence or establishment but may also have a lower probability of being ingested by frugivores or escaping from postdispersal seed predators. These conflictive pressures will consequently affect the optimal value of seed size in many species to maximize the fitness through the overall regeneration process.

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