Asymmetric effects of rodent-mediated seed dispersal on co-existence of tree species via seed–seed interactions

Abstract Asynchronous mast seeding of sympatric tree species can affect seed dispersal, but it is not clear how the relative abundances of seeds might influence indirect seed–seed interaction mediated by seed dispersal agents. In this study, we investigated how seed abundance variations of the two sympatric tree species (Quercus variabilis and Pinus armandii) with asynchronous masting events influenced seed dispersal in the eastern Qinling Mountains, China. Although seed removal and seed consumption were influenced by both seed abundance and seed species, seed caching was only species-dependent, i.e., Q. variabilis acorns were more likely to be cached than P. armandii seeds irrespective of seed abundance. The proportion of scatter-hoarded P. armandii seeds depended on the abundance of Q. variabilis acorns. Regardless of seed abundance, Q. variabilis acorns were dispersed further than P. armandii seeds. Our results collectively indicate that the ecological effects of indirect seed–seed interaction mediated by seed dispersers on seed dispersal are asymmetrical and are potentially regulated by seed abundance as well as seed species (or seed traits). We recommend future studies focus on indirect seed–seed interactions among multiple species with contrasting seed traits, to better understand how they influence seed dispersal, plant regeneration and dynamics.