The mechanisms behind the coexistence of competitor species is one the major questions of community ecology. One of the proposed mechanisms are trade-offs, such as the colonization-competition trade-off, in which species highly efficient in finding new resources are not able to fend off competitors, and species highly efficient in monopolizing resources are not efficient in finding them.

The colonization-competition trade-off seems to be the mechanism behind the coexistence of four ant species that inhabit acacia trees (Stanton et al. 2002). Acacia trees offer food and shelter for ants, which in turn defend the tree against herbivores, forming a mutualistic association. Young acacias can be colonized either by expanding ant colonies or by lone foundress queens, older trees can be seized by more competitive ants, and there is evidence for a colonization-competition trade-off in this system. Also, mature trees can lose their ants via droughts or fires, and these mature trees are high quality resources for new foundress queens. Even though colonization-competition trade-offs have been extensively modeled in different ways, this is an especially interesting case because the resource (acacia trees) has population dynamics of its own.

Propose a model that reproduces the community of acacia-ants described by Stanton et al. (2002) and that includes acacia tree population dynamics.

1) Can acacia tree dynamics facilitate or hamper ant species coexistence?
2) Is there an upper limit to the number of ant species that can coexist in this community?

Stanton, M. L., T. M. Palmer, and T. P. Young. Competition-colonization trade-offs in a guild of African Acacia-ants. Ecological Monographs 72.3 (2002): 347-363. LINK.