Ant-seed mutualisms: can red imported fire ants sour the relationship?

Invasion by the red imported fire ant, Solenopsis invicta, has had negative impacts on individual animal and plant species, but little is known about how S. invicta affects complex mutualistic relationships. In some eastern f orests of North America, 30% of herbaceous species have ant-dispersed seeds . We conducted experiments to determine if fire ants are attracted to seeds of these plant species and assessed the amount of scarification or damage that results from handling by fire ants. Fire ants removed nearly 100% of s eeds of the ant-dispersed plants Trillium undulation, T. discolor, T. cates baei, Viola rotundifolia, and Sanguinaria canadensis. In recovered seeds fe d to ant colonies, fire ants scarified 80% of S. canadensis seeds and destr oyed 86% of V. rotundifolia seeds. Our study is the first to document that red imported fire ants are attracted to and remove seeds of species adapted for ant dispersal. Moreover, fire ants might damage these seeds and discar d them in sites unfavorable for germination and seedling establishment. (C) 2001 Elsevier Science Ltd. All rights reserved.