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Effects of forest fragmentation on natural pollination, reproductive success and progeny vigor of Ceiba grandiflora .
Quesada, Mauricio*,1, Stoner, Kathryn1, Lobo, Jorge2, Palacios-Guevarra, Carolina1, Herreras, Yvonne1, 1 Instituto de Ecologia, UNAM, Morelia, Michoacan, MEXICO2 Universidad de Costa Rica, San Pedro, COSTA RICA
ABSTRACT- In this study we determined the effects of forest fragmentation on natural pollination, reproductive success and vigor of the offspring produced by the tree Ceiba grandiflora. First, we determined the mating system of C. grandiflora using hand pollinations and genetic analysis. Second, we evaluated the relationship between the natural deposition of pollen with respect to the production of fruits and seeds in isolated trees located in disturbed areas and with respect to trees in continuous forest. Finally, we compared survivorship and vigor parameters of the offspring of C. grandiflora produced by isolated trees with respect to trees in continuous forest. The study was conducted in tropical dry forest within and surrounding the Chamela-Cuixmala Biosphere Reserve, Mexico. Our results indicate that 1.3% of the flowers developed into fruit from the continuous populations whereas 0.8% developed into fruit from isolated trees. The population of C. grandiflora studied was predominantly outcrossing and fruits sired by several donors were more likely to develop to maturity. Flowers that set fruit received significantly more pollen grains in continuous populations than in isolated trees, an average of 450 and 216 pollen grains, respectively. Similarly, flowers that received less than 200 pollen grains were more likely to abort fruits in both tree conditions. The production of seeds was positively correlated to the amount of pollen received on the flower stigmas. The amount of pollen received by the flowers from trees in continuous populations produced progeny with greater leaf area and biomass as seedlings than the progeny produced from flowers with less pollen from isolated trees.
KEY WORDS: Forest fragmentation, Pollination ecology, Tropical dry forest, Plant reproductive success