Synzoochory selects for interannual variation in reproduction in perennial plants

Reproduction in perennial plants varies from relatively constant among years to production of massive and synchronousseed crops at irregular intervals, a reproductive strategy called mast seeding. The sources of that interspecific differences in the extent of interannual variation in seed production are largely unknown. We conducted a global meta-analysis of 706 studies across 407 species quantifying the interannual variability of seed crops of plants that differed in dispersal modes. Phylogenetic analysis indicated that interannual variation in seed production tends to be similar in related species owing to their shared evolutionary. Interannual variation in seed production was 1.21 times higher in synzoochorous compared to endozoochorous species. Moreover, production of small seeds was associated with higher interannual variation in seed production. In consequence, synzoochorous species producing small seeds are those characterized by largest interannual variation in seed production. Our study lends support to a long-standing notion that interspecific variation in masting intensity is largely shaped by the interactions of plants with animals. Masting is avoided when interannual variation in seed production can harm mutualists and promoted when satiation can decrease predation and increase seed dispersal.