Like many seed-harvesting ants, the western harvester ant (Pogonomyrmex occidentalis) can act as both a predator and a seed disperser. Dispersal results when seeds are dropped en route to the nest, are left in nest granaries when colonies die or are abandoned, or are removed from granaries and discarded in nest middens. This study examined the density and species identity of seeds discarded in harvester ant nest middens and compared them with those found in nearby soils. Nineteen species of seeds were recovered from middens, compared with 13 species in 5-m reference areas and 9 species in adjacent disk areas. Total density of sound seeds was nearly 3 times higher in middens than at 5 m from the nest and nearly 50 times higher than in disk soils. Moreover, 4 of the 6 most common species overall were significantly more abundant in middens. One species, Munro globemallow (Sphaeralcea munroana), was recovered from nearly 50% of middens but was not found in the other 2 areas. These findings suggest that the western harvester ant is a potentially important disperser of some sagebrush-steppe plant species.
Mull, John F.
"Dispersal of sagebrush-steppe seeds by the western harvester ant (Pogonomyrmex occidentalis),"
Western North American Naturalist: Vol. 63
, Article 9.
Available at: http://scholarsarchive.byu.edu/wnan/vol63/iss3/9