Myrmecochory in Viola: Dynamics of Seed-Ant Interactions in Some West Virginia Species

SUMMARY (1) The interactions of ants and diplochorous Viola seeds were studied at four forest and forest-edge sites in Monongahela National Forest, West Virginia. Of the nine Viola species studied, seeds of six (V. blanda, V. papilionacea, V. pedata, V. pensylvanica, V. rostrata and V. triloba) were readily taken. (2) The most important seed transporters were Aphaenogaster spp., but Formica subsericea, Lasius alienus, Leptothorax spp., Myrmica punctiventris and Tapinoma sessile also took seeds. Unlike the situation in Europe, ants of the Formica rufa group displayed little interest in Viola seeds. There was no evidence of specialization of particular ant species on particular Viola species. (3) Cleistogamous seeds were taken much less frequently than chasmogamous seeds, even though cleistogamous seeds had larger elaiosomes. This difference is apparently due to diet shifts of the ants in summer. (4) Most seeds picked up by ants were carried to the nest. The distances seeds were moved averaged about 75 cm, which is less than the average ballistic dispersal distance. (5) The advantage of ant dispersal is relocation to a 'safe site' for germination, thus reducing predation, increasing germination stimuli, and increasing the available supply of nutrients.