Selective Advantages to Hemi-Parasitic Annuals, Genus Melampyrum, of a Seed-Dispersal Mutualism Involving Ants: II. Seed-Predator Avoidance

Abstract

Field experiments were used to assess the importance of third species antagonists, in this case rodent seed-predators, in driving the evolution of seed dispersal by ants in the genus Melampyrum. Daytime and nighttime seed-removal frequencies were determined by placing seeds so that 1) ants and rodents had access, 2) only ants had access, 3) only rodents had access, and 4) neither ants nor rodents had access. Experiments were conducted with Melampyrum populations of three different species at four sites, two in the U.S. (M. lineare in Maine and Michigan) and two in Switzerland (M. arvense and M. silvaticum). Morning versus evening fruit dehiscence and the effect of elaiosome removal on seed-attractiveness to ants were also investigated