Effects of weevil larvae on acorn use by blue jays

Dixon, Mark D.; Johnson, William C.; Adkisson, Curtis S.

doi:10.1007/s004420050226

Cited by 40 publications

(27 citation statements)

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“…Nut foragers were able to discriminate seed infestation, preferring sound seeds to infested, in line with other studies about jays (Dixon et al, 1997) and rodents (Muñoz and Bonal, 2008b). Hence, sound seeds would have higher probability of being dispersed and they would be more likely to become established because sound seeds contain higher cotyledon mass (higher energy content).…”

Section: Discussionsupporting

confidence: 85%

“…rodents), which clearly preferred large and sound seeds over small and infested seeds (Steele et al, 1996;Muñoz and Bonal, 2008a,b). However, not all foragers show the same preferences for species or have the ability to discriminate some intrinsic seed properties (Cheng and Zhang, 2011;Dixon et al, 1997;Pons and Pausas, 2007b). Thus, different guilds of foragers may contribute differentially to the final seed removal due to dissimilarities in body size, habitat selection, seed preferences or foraging behavior.…”

Section: Introductionmentioning

confidence: 99%

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Flying vs. climbing: Factors controlling arboreal seed removal in oak–beech forests

Perea

Miguel

Gil

2011

Forest Ecology and Management

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Keywords:Seed size Seed infestation Foragers density Removal speed Fagus sylvatica QuercusNuts are heavy and nutritious seeds that need animals to be successfully dispersed. Most studies address nut removal by a single animal species once seeds fall onto the ground. However, nuts are also accessible before the seed drop and usually to a wide guild of seed foragers. This study examines the factors controlling arboreal seed removal in oak-beech forests within the whole guild of nut foragers. We found that seed-dispersing rodents (Apodemus sylvaticus) were the main acorn removers in the oaks (up to 3.75 m height), with a rapid seed encounter and a high removal rate. However, rodents did not climb the beech trees, probably due to their smoother bark in comparison to oak bark and/or the lower nutritional value of beechnuts with regard to acorns. Jays (Garrulus glandarius) were more abundant in oak stands (both dense and scattered) and clearly preferred acorns to beechnuts whereas nuthatches (Sitta europaea) were more abundant in beech stands and preferred beechnuts to acorns. Non-storing birds such as great tits (Pants major) also removed acorns and beechnuts, especially in the stands where oaks are dominant. Jays and rodents preferred sound seeds over insect-infested seeds but such a preference was not found for nuthatches. This study highlights that pure beech stands showed a reduced guild of arboreal nut foragers in comparison to oak stands. This different guild could probably affect the spatial patterns of seed dispersal, with a proportionally higher number of long dispersal events for acorns (mostly jay-dispersed) than for beechnuts (mostly nuthatch-dispersed). Long-distance dispersal of beechnuts (by jays) is determined by the presence of other preferred species (oaks) and their frequency of non-mast years. Seed location in different habitats strongly determines the contribution of different arboreal removers (including climbing rodents) and their removal speed, leading to a differential seed fate that will eventually affect tree regeneration. As nuthatches are sedentary birds, it is important to maintain old and dead trees where they can breed (crevices), forage (arthropods) and store seeds in order to favor beechnut dispersal and gene flow. By maintaining or favoring oak trees within beech stands we will ensure a wider guild of arboreal nut dispersers.

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Section: Discussionsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Flying vs. climbing: Factors controlling arboreal seed removal in oak–beech forests

Perea

Miguel

Gil

2011

Forest Ecology and Management

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“…In the case of acorns, few studies have reported predation on pre-dispersal granivorous insects by birds (e.g. Dixon et al 1997) or by small mammals (Steele et al 1996). With respect to them, the present study also includes ungulates, major acorn predators that had not been considered in this kind of multitrophic interaction to date.…”

Section: Discussionmentioning

confidence: 96%

Multi-trophic effects of ungulate intraguild predation on acorn weevils

Bonal

Muñoz

2007

Oecologia

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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.

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“…Insects may actively render seed or fruit unpalatable or unusable to vertebrates as a strategy to maximize the amount of food available to themselves (Janzen 1977). Nevertheless, vertebrates sometimes do not differentiate between sound and infested seeds or fruits (Dixon et al 1997, Weckerly et al 1989, or even prefer insect-infested seeds and fruits to sound ones (Sallabanks & Courtney 1992, Semel & Andersen 1988, Steele et al 1996, Valburg 1992. Possible reasons for vertebrates to prefer infested seeds include: (1) seeds with larvae having a higher nutritional value than sound ones, because larvae synthesize fat and/or proteins (Sallabanks & Courtney 1992, Valburg 1992 or other nutrients such as vitamins (Havera & Smith 1979, Semel & Andersen 1988, Steele et al 1996; (2) seeds with larvae tasting better than sound seeds (Borowicz 1988); and (3) seeds with larvae may be more easily opened and consumed than sound seeds (Borowicz 1988).…”

mentioning

confidence: 99%

Bruchid beetle infestation and the value of Attalea butyracea endocarps for neotropical rodents

Gálvez

Jansen

2007

J. Trop. Ecol.

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Frugivorous and granivorous vertebrates often discriminate against seeds and fruits infested by insects (Sallabanks & Courtney 1992). Insects may actively render seed or fruit unpalatable or unusable to vertebrates as a strategy to maximize the amount of food available to themselves (Janzen 1977). Nevertheless, vertebrates sometimes do not differentiate between sound and infested seeds or fruits (Dixon et al. 1997, Weckerly et al. 1989), or even prefer insect-infested seeds and fruits to sound ones (Sallabanks & Courtney 1992, Semel & Andersen 1988, Steele et al. 1996, Valburg 1992). Possible reasons for vertebrates to prefer infested seeds include: (1) seeds with larvae having a higher nutritional value than sound ones, because larvae synthesize fat and/or proteins (Sallabanks & Courtney 1992, Valburg 1992) or other nutrients such as vitamins (Havera & Smith 1979, Semel & Andersen 1988, Steele et al. 1996); (2) seeds with larvae tasting better than sound seeds (Borowicz 1988); and (3) seeds with larvae may be more easily opened and consumed than sound seeds (Borowicz 1988).

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Effects of weevil larvae on acorn use by blue jays

Cited by 40 publications

References 41 publications

Flying vs. climbing: Factors controlling arboreal seed removal in oak–beech forests

Flying vs. climbing: Factors controlling arboreal seed removal in oak–beech forests

Multi-trophic effects of ungulate intraguild predation on acorn weevils

Bruchid beetle infestation and the value of Attalea butyracea endocarps for neotropical rodents

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