Fruit Flags: Two Hypotheses

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Abstract
Signals that identify the presence and availability of fruits ready for dispersal probably increase the rates of seed dissemination for bird-dispersed seeds. The 2 hypotheses presented illustrate how fruit flags may increase conspicuousness of fruiting species thereby increasing visitation by frugivorous birds. In temperate deciduous forests, foliar fruit flagging species lose energy from photosynthesis by changing leaf color early, but create a large contrasting signal. The contrasting leaves may attract migrant frugivores that are unfamiliar with resource locations at any given stopover point along their migratory route. Contrasting long-distance fruit flags may also be important for some tropical plant species. Preripening fruit flags do not create a long-distance signal but rather alert resident frugivores to the presence of fruit that will soon ripen. This increases the probability that resident frugivores will remove the fruit and disseminate the seeds before the fruits are rendered unacceptable through microbial attack. This pattern is found in both tropical and temperate systems.