Seed dispersal in the myrmecochorous herb, Trillium grandiflorum.

Abstract

Myrmecochory (ant-dispersal) may have evolved in response to seed predation by small mammals. A myrmecochorous species, Trillium grandiflorum, was studied in northern Michigan, to test the prediction that the presence of ants reduces the rate of seed predation by rodents. Seed removal rates were recorded on four different treatments; (a) ant only access, (b) rodent only access, (c) ant/rodent combined access, (d) no ant/no rodent access in two separate trials. The proportion of T. grandiflorum lost to seed predators varied between trials, but differences in removal rates were not significantly different between the treatments. Trends emerged indicating that ants remove more seeds than rodents. When ants and rodents had access to seeds on the same treatment, there was a lower rate of removal than anticipated when removal rates for separate ant and rodent treatments were combined. Overall seed removal was much lower than expected but the data were suggestive of ant presence resulting in reduction of rodent seed predation.