Making dispersal syndromes and networks useful in tropical conservation and restoration
Howe, Henry F.
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Dispersal syndromes and networks must be used cautiously in conserving and restoring seed-dispersal processes. In many tropical forests most tree and shrub species require dispersal by animals for local persistence and for migration in response to environmental change. The most important errors to avoid in practical use of both dispersal syndromes (suites of fruit and seed characteristics that attract different dispersal agents) and network modules (groups of interacting dispersal agents and plants bearing fruits or seeds that they eat) are: (1) assuming that use of fruit resources by fruit-eating animals implies effective seed dispersal; (2) assuming that superficially similar fruits imply equally effective dispersal by similar animals, and (3) assuming that fruit resources at issue support animal populations. This essay explores strengths and weaknesses of uses of dispersal syndromes and disperser networks modules in conservation and restoration. Examples include some that are consistent with expectations from syndrome categorization and some that are not. An unappreciated weakness in using either dispersal syndromes or network modules is that contingent foraging by animals in highly disturbed habitats, now comprising 60%-70% of tropical land biomes, may not resemble foraging choices or consequences in protected closed forests, where most research on tropical seed dispersal is done. General prescriptions for the future include maintaining or creating habitat heterogeneity in largely deforested landscapes where remnant closed forests still exist, and active restoration in landscapes where little heterogeneity remains. In both cases, adaptations of multiple frame-work tree approaches have the best chance of preserving or enhancing populations of animal-dispersed trees and their seed vectors, and in opening migration paths in response to climate change.
Restoring dispersal processes