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Changes in Sexual Expression as Result of Defoliation and Environment in a Monoecious Shrub in Mexico: Implications for Pollination

Arceo-Gómez, Gerardo, Parra-Tabla, Víctor, Navarro, Jorge
Biotropica 2009 v.41 no.4 pp. 435-441
Cnidoscolus aconitifolius, deciduous forests, defoliation, female flowers, females, herbivores, male flowers, males, pastures, pollination, shrubs, Mexico
Folivory may indirectly impact plant reproduction through changes in sexual expression (i.e., number or proportion of male and female flowers produced), which influence plant-pollinator interactions via changes in pollinator preference or efficiency. This study is an experimental evaluation of the effect that defoliation has on sex expression in the monoecious shrub Cnidoscolus aconitifolius, how such effect varies across sites, as well as how such changes indirectly affect pollinator visitation rates. The present study used three populations of C. aconitifolius, each one located in a different site in Yucatán (México): pasture, deciduous forest and subdeciduous medium height forest and three levels of defoliation: 50 percent, 100 percent, and a control (no damage). Results showed that defoliation reduced significantly the total number of male flowers produced in two of the sites. Defoliation did not impact female flower production or the proportion of female flowers produced. Finally, floral visit rates were not affected by defoliation via changes in sexual expression and neither by site or by the interaction site x defoliation. Findings showed that defoliation had an effect on sex expression in C. aconitifolius, although apparently this change did not affect the plant-pollinator interactions.