Acacia-ant symbiosis
Acacia-ant symbiosis is the interaction between myrmecophilous Vachellia trees and ants that nest on them. Obligate acacia ants dwell in the gall-like domatia within the swollen stipular spines, and prickles|spines] of African or Central American ant acacia species, and they also take the food offered by the tree. Some of them protect ant acacias from herbivores in return, hence mutualism; the others provide inadequate protection or none at all, hence weaker or non-mutualism. Facultative acacia ants often nest on stems instead of in gall-like domatia, and tend to be non-mutualistic.
Africa
Four acacia ant species are symbiotic with Vachellia drepanolobium: Crematogaster mimosae, C. nigriceps, and Tetraponera penzigi are obligate and mustualistic symbionts, whereas C. sjostedti is facultative and the least mustualistic, and it even facilitates attack on the tree by beetles.Vachellia bullockii, V. burttii, V. bussei, V. elatior, V. erioloba, V. erythrophloea, V. luederitzii var. retinens, V. malacocephala, V. mbuluensis, V. myrmecophila, V. pseudofistula, V. seyal var. fistula, and V. zanzibarica are also known to have gall-like domatia, but their symbiotic ants are yet to be studied.
Central America
The following are 10 obligate and mutualistic acacia ants and their reported host plants in Central America:- Pseudomyrmex ferruginea: Vachellia allenii, V. chiapensis, V. collinsii, V. cookii, V. cornigera, V. gentlei, V. globulifera, V. hindsii, V. janzenii, V. mayana, and V. sphaerocephala
- P. flavicornis and P. nigrocinctus: V. collinsii, V. cornigera, and V. hindsii
- P. janzeni: ''V. hindsii
- P. mixtecus and P. veneficus: V. collinsii and V. hindsii
- P. particeps: V. allenii
- P. peperi: V. chiapensis, V. collinsii, V. cornigera, V. gentlei, V. globulifera, and V. hindsii
- P. satanicus: V. melanoceras
- P. spinicola: V. collinsii, V. cornigera, and V. allenii
Facultative acacia ants in Central America include P. boopis, P. gracilis, P. hesperius, P. ita, P. kuenckeli, P. opaciceps, Crematogaster and Camponotus species.
Some swollen-spine acacias in Central America are less dependent on acacia-ant mutualism and often unocuppied by obligate acacia ants without being significantly damaged by herbivores, e.g. V. cookii, V. globulifera, and V. ruddiae''.