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Context-dependent recruitment of Guettarda viburnoides in a Neotropical forest-savanna mosaic

Abstract:

Premise of the Study: Seed dispersal is a key process for plant regeneration in tropical areas. Differences in disperser behavior result in a nonrandom distribution of seeds among habitats. Patterns of seed dispersal may cascade through the entire recruitment phase or uncoupling between developmental stages may occur such that patterns of seed dispersal are discordant with patterns of recruitment. Here, we analyzed how habitat and interannual variability affect the recruitment dynamics of a birddispersed tree, Guettarda viburnoides (RUB.). Methods: Over 3 years, we determined the habitats where seeds of G. viburnoides are dispersed, and we experimentally quantified postdispersal seed predation, seedling emergence, and survival in four habitats of a forest - savanna mosaic in Bolivia. Key Results: Habitat affected seed dispersal, seed predation, and seedling emergence. The strength of postdispersal processes, however, varied between years and no consistent within-habitat pattern emerged. Uncoupling among different life-stages was observed across habitats, and spatial concordance was found between seed rain and sapling recruitment patterns. Conclusions: Habitat can affect seed dispersal, postdispersal processes and the recruitment dynamics of a Neotropical tree in a heterogeneous landscape. Additionally, our results show interannual variability in the strength of postdispersal processes, which leads to shifts in habitat suitability between years. Therefore, to better understand the role of site suitability for recruitment, we need to explicitly consider not only variation in habitat-specificity for dispersal and postdispersal processes, but also how this variation can shift under different environmental conditions - that is, the context dependence of suitability. © 2011 Botanical Society of America.