, Volume 152, Issue 3, pp 533–540 | Cite as

Multi-trophic effects of ungulate intraguild predation on acorn weevils

Plant Animal Interactions


Predators and parasitoids may contribute to controlling the population sizes of phytophagous insects, and this has been shown to benefit plants. Phytophagous insects may also be killed by other herbivores (intraguild predation), usually larger-sized vertebrates that ingest insects accidentally while feeding on common food sources. We studied the intraguild predation on acorn weevils by ungulates and assessed the consequences for weevil populations. Infested acorns are prematurely abscised and the weevil larvae finish their development inside the acorns after being dropped. Our results show that weevil larvae were killed by ungulates eating the infested acorns on the ground. Ungulates did not discriminate between infested and sound acorns, and the probability of a larva being incidentally eaten was inversely related to acorn availability. Thus, predation risk was enhanced by the premature drop of infested acorns when acorn availability on the ground was low. Predation rates on infested acorns were much higher where ungulates were present, and acorn infestation rates were significantly lower. However, ungulates did not provide the oaks any net benefit, since the reduction of infestation rates was not enough to compensate for the large amounts of sound acorns eaten by ungulates. Seed predation is usually studied as a progressive loss of seeds by pre- and post-dispersal predators, but the interactions between them are usually not considered. We show that intraguild predation on insects by large ungulates had an effect on the structure of the foraging guild, as the proportion of acorns predated by insects decreased; however, replicating the same experimental design in different ecological scenarios would increase the strength of these results. In conclusion, the present study shows the importance of considering the multi-trophic interactions between seed predators in order to have a complete picture of granivory.


Intraguild predation Multi-trophic interactions Seed abscission Pre-dispersal seed predation Acorn 



Comments of M. Diaz, C. Smit, J. M. Aparicio and M. T. Monaghan improved previous versions of this manuscript. L. Arroyo, B. A. Nicolau and N. Fermin helped with the fieldwork. J. Jimenez allowed and provided facilities for fieldwork at Cabañeros National Park. This study was supported by the projects REN2003-07048/GLO of the Ministerio de Ciencia y Tecnología, PAC-02-008 of the Junta de Comunidades de Castilla-La Mancha and 096/2002 of the Ministerio de Medio Ambiente. R. B. and A. M. were supported by fellowships from La Junta de Comunidades de Castilla La Mancha.


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Departamento de Ciencias Ambientales, Facultad de Ciencias del Medio AmbienteUniversidad de Castilla–La ManchaToledoSpain
  2. 2.Department of EntomologyNatural History Museum LondonUK

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