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Résumé :
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P>1. Many plant species depend upon animals for seed dispersal, yet animals disperse seeds in pursuit of their own social and behavioural agendas. Animal social behaviour affects where and how they forage, so it must also shape patterns of seed dispersal. 2. At Sedgwick Reserve, California, USA, we established a study population of Quercus agrifolia to determine patterns of acorn foraging by the acorn woodpecker (Melanerpes formicivorous). This cooperative breeder lives in social groups that defend territories surrounding arboreal seed caches (granaries), foraging communally within these territories. 3. We genotyped pericarp tissue of 568 acorns, as well as 285 adult Q. agrifolia trees, including all adults within 150 m of 16 focal granaries. After quantifying genotyping error, we identified a genetically reliable subset of 524 acorns. We assigned a source tree to each acorn and estimated the number of seed sources per granary and seed source sharing among granaries. 4. We found one to eight distinct seed-source genotypes per granary, and an effective source diversity ranging from 1.0 to 6.6 seed sources. Of all transport events, 96.5% involve source trees within 150 m of the granaries. For one granary, all sampled acorns were transported from five trees located more than 1.3 km away, with all source trees within
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