Oecologia

, Volume 156, Issue 1, pp 137–145 | Cite as

Fruit tracking, frugivore satiation, and their consequences for seed dispersal

Plant-Animal Interactions - Orignal Paper

Abstract

Vertebrate frugivore communities are easily satiated by abundant fruit supplies and, contrary to abiotic dispersal agents, typically disperse only part of the available seed pool. This frugivore satiation is likely to be a widespread phenomenon and should be an influential predictor of plants’ ability to disperse their offspring to suitable establishment sites; yet it has never been systematically quantified. Here I investigate patterns of fruit abundance, frugivore activity and frugivore satiation, and their consequences for seed dispersal in the fleshy-fruited tree Frangula alnus. Based on constant-effort seed trapping conducted over 3 years, I assess densities of total and frugivore-consumed seedfall across two spatial (within/between populations) and two temporal (within/between ripening seasons) scales. Furthermore, I examine relationships between fruit abundance and the amount of seeds that are actually dispersed away from fruiting trees. Frugivore activity tightly matched fruit abundance, although some differences existed between scales. This marked fruit tracking did not prevent a significant frugivore satiation, however, and only 53% of the available fruit crops were actually consumed. The extent of satiation varied most at the within-population level, likely due to the territorial behaviour of important frugivore species. In contrast, levels of satiation remained remarkably invariable through time, suggesting that frugivores behave as opportunists and closely adjust the composition of their diet to the available food supply. Overall, greater fruit abundance resulted in a higher proportion of seeds falling beneath fruiting trees, but it also helped increase the (absolute) number of seeds dispersed. This study shows that frugivore satiation can be an important phenomenon even when frugivores tightly track fruit abundance. Its negative effects on recruitment may be attenuated, however, if greater fruit crops help increase population-wide frugivore activity and the amount of seeds being dispersed to suitable establishment sites.

Keywords

Crop size Dispersal limitation Frugivory Resource tracking Seed rain 

Notes

Acknowledgements

I thank the staff of the Los Alcornocales Natural Park for the permission and logistic support I received during fieldwork. Enrico Rezende and Pedro Jordano provided valuable help with some of the statistical analyses and thoughtful comments from Luc Barbaro, Kevin Burns, Jacqui Shykoff, and an anonymous reviewer helped improve a previous version of the text. Fieldwork was funded by the Spanish Ministry of Science and Technology (grants PB98-1144, BOS2002-01162 and REN2003-00273) and final elaboration by a Marie Curie postdoctoral fellowship of the European Union (grant MEIF-CT-2006-025383). Thus study was conducted in compliance with Spanish legislation.

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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.INRAUMR 1202 Biodiversity, Genes and Communities (BIOGECO)Cestas CedexFrance
  2. 2.Integrative Ecology GroupEstación Biológica de Doñana, CSICSevillaSpain

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