Food competition as catalyst of a seed-dispersal mutualism:conditional interactions among Wild Boar, Wood Mouse and Pedunculate Oak.
10 / 2009 - 09 / 2013
The importance of conditionality ? dependence on external circumstances ? is increasingly recognized across species mutualisms, but has rarely been quantified, and its broader ecological and evolutionary consequences remain largely unexplored. Here, we propose to study how the outcome of a plant-animal interaction is affected by food competition.
We will experimentally investigate the role of a seed-hoarding rodent ? Wood mouse (Apodemus sylvaticus) ? as seed disperser and seed predator of a large-seeded tree species ? Pedunculate oak (Quercus robur) ? in a multi-trophic system. Our hypothesis is that the rodents will behave more as mutualists as they experience more food competition from conspecifics and a third species ? Wild boar (Sus scrofa): they will hoard more acorns, and ?scatter-hoard? these in more widely spaced shallow caches with one or few seeds each, some of which will produce seedlings. Under low food competition, in contrast, the rodents will tend to ?larder-hoard? seeds in burrows where all seeds die.
To test this hypothesis, we will compare the hoarding behaviour of mice between forests with and without presence of wild boar, and between years with high and low acorn production. We will carry out field experiments at locations along impassable highways at the Veluwe in the Netherlands with high populations of wild boar on one side and none on the other side, and do so in multiple years with contrasting seed production. At all locations, we will individually tag acorns with inserted transponders, video-record acorn removal, relocate the dispersed acorns with a customized transponder reader to determine how and where the acorns have been hoarded, and follow acorn fates till death or germination. Four parallel experiments we will unravel the factors underlying observed patterns.
The results of this study will increase the fundamental insight in the dynamics of species interactions and the circumstances that can influence the outcome of these interactions. Moreover, the results will increase our knowledge on the ecological roles of wood mouse and wild boar, which may contribute to a more sound management of forest and wildlife.