Fragmentation modifies seed trait effects on scatter-hoarders’ foraging decisions

DÍAZ, M.; TIRIBELLI, F.; TRAVESET, A.; PÉREZ-SEPÚLVEDA, J. E.; VALLADARES, F.; MORÁN-LÓPEZ, T.

PLANT ECOLOGY

SPRINGER

Lugar: Berlin; Año: 2018 vol. 219 p. 325 - 342

1385-0237

Scatter-hoarding animals are crucial inseed dispersal of nut-bearing plants. We used the holmoak Quercus ilex?wood mouse Apodemus sylvaticusmutualism as a model system to evaluate the relativeimportance of seed size and fat content on scatterhoarders?foraging decisions influencing oak dispersaland potential recruitment. We performed a fieldexperiment in which we offered holm oak acorns withcontrasting seed size (2 vs 5 g) and fat content (3 vs11%). Moreover, to test if the strength of these seedtrait effects was context-dependent, experimentalacorns were placed in small fragments, where naturalregeneration is scarce or absent, and forest habitats. Insmall fragments, rodents had to face increasedintraspecific competition for acorns and reducedanti-predator cover during transportation. As a result,they became more selective to ensure rapid acquisitionof most valuable food items but, in turn, transportedseeds closer to avoid unaffordable predation risks.During harvesting and caching, larger acorns wereprioritized and preferentially cached. Fat content onlyhad a minor effect in harvesting preferences. Incontrast, in forest sites, where rodent abundance wasfour times lower and understory cover was welldeveloped,rodents were not selective but providedenhanced dispersal services to oaks (caching rateswere 75% higher). From the plants? perspective, ourresults imply that the benefits of producing costlyseeds are context-dependent. Seed traits modifiedharvesting and caching rates only when rodents wereforced to forage more efficiently in response toincreased intraspecific competition. However, whenlandscape traits limited cache protection strategies, amore selective foraging behavior by scatter-hoardersdid not result in enhanced dispersal services. Overall,our result shows that successful dispersal of acornsdepends on how specific traits modulate their valueand how landscape properties affect rodents? ability tosafeguard them for later consumption.