Effectiveness of Spider Monkeys (Ateles geoffroyi vellerosus) as Seed Dispersers in Continuous and Fragmented Rain Forests in Southern Mexico
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Seed dispersal is considered a key process determining spatial structure and dynamics of plant populations, and has crucial implications for forest regeneration. We evaluated the effectiveness of spider monkeys (Ateles geoffroyi) as seed dispersers in continuous and fragmented habitats to test if this interaction is altered in forest fragments. We documented fruit and seed handling, defecation patterns, diversity and composition of seeds in feces, and seed germination of defecated and control seeds in the Lacandona rainforest, Mexico. For most species contributing to 80% of total fruit feeding time, monkeys swallowed and spat seeds, but swallowing was the most frequent seed handling category in continuous and fragmented forests. However, the proportion of feeding records of swallowed seeds was higher in continuous forest (0.59) than in fragments (0.46), whereas the opposite was true for proportion of dropped seeds (0.16 vs. 0.31). This pattern was reflected in the number of fecal samples containing seeds, which was greater in continuous (95.5%) than in fragmented forests (82.5%). Seeds in fecal samples included a total of 71 species from 23 plant families. The numbers of defecated seed species were similar between forest conditions, and in both cases most seeds (>86%) were undamaged. Defecated seeds showed greater germination percentages than control seeds in all of the five species evaluated. Although we identified some differences in seed handling and the percentage of feces with seeds between continuous forest and fragments, our results indicate that, in general terms, spider monkeys are effective seed dispersers in both forest conditions.
KeywordsForest regeneration Fragmentation Frugivorous primates Seed dispersal
This research was supported by grants from the Consejo Nacional de Ciencia y Tecnología, México (CONACyT Grant CB-2005-51043 and CB-2006-56799). This article constitutes a partial fulfillment of the Graduate Program in Biological Sciences of the National Autonomous University of México (UNAM). The organization Idea Wild provided equipment. This study would not have been possible without the collaboration of the local people in Loma Bonita, Chajul, Reforma Agraria, and Zamora Pico de Oro ejidos. V. Sork, D. Scofield, P. Thompson, and M. Quesada provided useful comments and suggestions in advanced drafts of this article. We thank C. Hauglustaine, C. Balderas, S. Martínez, J. Herrera, A. González-Di Pierro, and R. Lombera for field assistance. J. Rodríguez collaborated in the identification of seeds, and J. M. Lobato, G. Sánchez, H. Ferreira, and A. Valencia provided technical support. We also thank J. M. Setchell, E. W. Schupp, and 1 anonymous reviewer for valuable criticisms and suggestions that improved the manuscript.
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