Journal
ECOLOGY
Volume 91, Issue 1, Pages 155-165Publisher
WILEY
DOI: 10.1890/08-2115.1
Keywords
autonomous self-pollination; Dominican Republic; generalized pollination; Gesneriaceae; pollen limitation; Puerto Rico; reproductive assurance; specialized pollination
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Funding
- American Gloxinia and Gesneria Society
- Explorers Club-Washington Group
- Graduate Woman in Science
- Sigma Xi
- University of Maryland
- NSF [DDIG 0710196]
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Pollen limitation of female fecundity is widespread among angiosperms, a signal that pollinators frequently fail to transfer pollen to fertilize all ovules. Recent surveys have suggested that pollen limitation is associated with floral specialization. This Study uses a group of Antillean Gesneriaceae with contrasting pollination systems (bat, hummingbird, and generalist) to assess the premise that plants with specialized pollination systems and infrequent pollinator Visitation experience greater pollen limitation Of fruit and seed set than their generalist congeners. Alternatively, specialists may possess mechanisms that reduce pollen limitation such as autonomous self-pollination. A survey of autonomous Self-pollination conducted on 13 Gesneria and Rhytidophyllum species during 2006-2008 revealed no significant association between reproductive assurance mechanisms and pollination system specialization. However, high levels of potential autonomous self-pollination were Only found among specialized hummingbird-pollinated species. A comparison of fruit and seed set between emasculated and unmanipulated flowers provided evidence for autonomous selfing acting as I reproductive assurance mechanism in three out of four ornithophilous species. Furthermore. the Puerto Rican population of G. reticulata relies almost exclusively on self-pollination for reproduction. Two-year pollen supplementation experiments conducted on nine Gesnerieae species from the Dominican Republic and Puerto Rico provided evidence for significant pollen limitation associated with pollination specialization including both bat- and hummingbird-pollinated Gesnerieae, no pollen limitation was detected in any of the four generalist species. No pollen limitation was detected either in two ornithophilous Gesneria species with low hummingbird visitation and high levels of autonomous self-pollination. This Study provides Support for the idea that generalized pollination systems may, in some cases. buffer against fluctuations in the pollinator environment. However, the use of reproductive assurance mechanisms allows the maintenance of highly specialized pollination systems ill pollinator depauperate environments.
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