Seeds may have more than one opportunity of being dispersed. After a first phase consisting of the initial movement of seeds away from mother plant (primary dispersal), there may be a second phase (secondary dispersal) in which seeds are further dispersed, usually by another mechanism or agent. This is common in plants which are first dispersed by endozoochory or ballistically and are subsequently moved by ants, dung beetles, rodents, birds, or even predators of such frugivores that carry seeds in their digestive tracts (the latter has been reported, for instance, for several species in the Canary Islands that are primarily dispersed by reptiles and secondarily dispersed by shrikes and raptors; Figure 2). There are cases where seeds have reward structures to attract ants, such as elaiosomes or flesh appendages, which are removed once the seeds are dispersed (in Rhamnus, Euphorbia, etc.). In other species, however, primarily dispersed seeds are removed by seed predators (rodents, granivorous ants, etc.) that store a fraction of them in sites like holes in trees or in soil, ant nests, etc., and later 'forget' to collect them; in some cases, these sites are especially suitable for further seedling emergence and establishment.
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