Context-dependent seed dispersal determines acorn survival of sympatric oak species

Abstract

Seed traits play an important role in seed dispersal and possibly in eventual plant community structure and dynamics. Though seed traits have been shown to influence seed dispersal of one given tree species, it is not clear if and how seed dispersal and seed survival of one tree species are affected by neighboring tree species at inter-specific level. In the present study, we investigated acorn dispersal of two oak species Q. variabilis (bearing large acorn) and Q. serrata var. brevipetiolata (bearing small acorn) in the presence of sympatric Q. aliena acorns (medium size), to test the ‘context-dependent’ hypothesis, which states that seed dispersal patterns of one tree species can be affected by sympatric tree species at inter-specific level. Our results showed that the probability of acorn removal of Q. variabilis was higher in the presence of Q. aliena acorns. However, the presence of Q. aliena acorns significantly decreased acorn removal rates of Q. serrata var. brevipetiolata. Acorns of Q. serrata var. brevipetiolata were less likely to be cached by small rodents in the presence of Q. aliena acorns, whereas, acorns of Q. variabilis tended to be scatter-hoarded in the presence of Q. aliena acorns. The presence of Q. aliena acorns promoted Q. variabilis acorns to establish seedlings, but arrested seed-seedling transition in Q. serrata var. brevipetiolata. Our study verifies the interspecific interactions of seed dispersal systems of sympatric oak species, showing the ‘context-dependent’ hypothesis that seed dispersal of one given tree species can be regulated by another or more sympatric tree species bearing seeds with contrasting traits.