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Fruit production in iteroparous flowering plants can be limited by a variety of conditions that need not be mutually exclusive nor immediately evident. We examined short- and long-term constraints to fruit production in a Puerto Rican population of the infrequently pollinated orchid Epidendrum ciliare. Average natural fruit maturation rate ranged from 5 to 15% over 4 yr. To evaluate limitations to fruit production, pollinations were augmented for a randomly chosen experimental portion of a population for two consecutive years. During this period, only 10 and 15% of flowers on control plants were naturally pollinated. Hand-pollinations of nearly all flowers produced by experimental plants increased fruit production to 33 and 49%, compared to 5 and 8% for controls. Thus, fruit production within seasons was partially limited by pollinations. Fruit predation also was heavy for both control (28 and 29% of fruits initiated) and pollination-augmented (20 and 32%) groups. No clear relationship existed between treatment and predation frequency. Furthermore, undamaged fruits often aborted (controls 11 and 37%, experimentals 15 and 28%), but frequencies were independent of self vs. outcrossed pollination and treatment. Seed crop mass declined as fruit set increased, suggesting that resources were limited. Long- term effects of heavy fruit loads were evident. Over 2 yr, the number of inflorescences, flowers, and flowers per inflorescence declined for experimentals relative to the controls. Moreover, plant size and vegetative proliferation decreased for experimentals relative to controls. Thus, through elevated fruit production the plant incurs future costs and lifetime fitness of E. ciliare might be more affected by resource constraints than by the other factors studied. |
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