A role for indirect facilitation in maintaining diversity in a guild of African acacia ants

• Published in: Ecology (Durham) 2013-07, Vol.94 (7), p.1531-1539
• Main Authors: Palmer, Todd M., Stanton, Maureen L., Young, Truman P., Lemboi, John S., Goheen, Jacob R., Pringle, Robert M.
• Format: Article
• Language: English
• Subjects: Acacia; Acacia - physiology; acacia ants; Acacia drepanolobium; Africa; Animal and plant ecology; Animal, plant and microbial ecology; Animals; ant-plant interactions; Ants; Ants - classification; Ants - physiology; Biodiversity; Biological and medical sciences; competition; Competitive Behavior; Ecological competition; Female; field experimentation; Flowers & plants; Formicidae; Fundamental and applied biological sciences. Psychology; General aspects; Habitats; Host plants; indirect facilitation; Insect colonies; Insect ecology; Insects; nesting; Plant spines; Plants; Population Dynamics; Queen insects; Saplings; Species; species coexistence; trees
• ISSN: 0012-9658; 1939-9170
• DOI: 10.1890/12-1873.1

Determining how competing species coexist is essential to understanding patterns of biodiversity. Indirect facilitation, in which a competitively dominant species exerts a positive effect on one competitor by more strongly suppressing a third, shared competitor, is a potentially potent yet understudied mechanism for competitive coexistence. Here we provide evidence for indirect facilitation in a guild of four African Acacia ant species that compete for nesting space on the host plant Acacia drepanolobium , showing that a competitively dominant acacia ant species indirectly creates establishment opportunities for the most subordinate species that may help to maintain diversity. Using long-term observational data and field experiments, we demonstrate that the competitively dominant ant species outcompetes two competitively intermediate species, while tolerating colonies of the subordinate competitor; this creates opportunities for local colonization and establishment of colonies of the subordinate species within the dominant species' territories. Host plants occupied by this subordinate species are then more likely to be colonized by the intermediate species, which in turn are more likely to be displaced by the dominant species. This process has the potential to generate a cyclical succession of ant species on host trees, contributing to stable coexistence within this highly competitive community.