Seed dispersal in the Iberian pear, Pyrus bourgaeana: A role for infrequent mutualists

Seed dispersal by animals is a key interaction, with effects on the population ecology and evolution of many plant lineages. Despite the fact that infrequent seed dispersers can potentially provide important services to plant populations, little attention has been paid so far to scarce mutualists. We assessed different aspects of quantity and quality of seed dispersal from fruit removal to seed germination in the Iberian pear, Pyrus bourgaeana, finding that fruit consumers markedly differed in the nature of their interaction with the tree. Whereas the abundant rodents, rabbits, and deer damaged all seeds eaten, the uncommon carnivores badger and fox and the abundant boars dispersed a large fraction of ingested seeds as viable propagules, acting as legitimate seed dispersers. Despite low rates of visitation by badgers to fruiting trees, they transported more viable seeds than the abundant boars, due to better seed treatment and a higher feeding rate on pears. Seed dispersal by all 3 legitimate dispersers, especially the badger, enhanced post-dispersal P. bourgaeana seed survival, supporting the escape predation hypothesis. Pyrus bourgaeana showed relatively high frequencies of visits by a myriad of frugivores; however, it relied on the dispersal service provided by an infrequent carnivore, the badger, rather than on those provided by the abundant mammalian herbivores. Therefore, under some circumstances, uncommon animal counterparts play major roles in their mutualistic interactions with flowering plants.