Vachellia collinsii
Vachellia collinsii is a thorny shrub or small tree in the pea family, Fabaceae, found in southern Mexico and Central America. Older botanical names include Acacia collinsii and Acacia costaricensis.[1] It is an ant-associated plant: ants occupy its hollow thorns and receive food from the tree, while helping to defend it against other organisms.[2]
Description
Trees may reach ten metres tall. The leaves are divided twice, with numerous pairs of oblong leaflets. Swollen, paired thorns occur at the leaf bases. Several small nectar-producing glands are clustered near the base of each leaf stalk. Yellowish flowers form narrow cylindrical spikes, rather than the round flower heads of some other thorn trees.[3]
The dark, leathery seed pods are usually 3–6 cm long, with a short beak at the tip. They split along both seams and contain brown seeds surrounded by yellow tissue. The taxonomic account records flowering between January and August across the material it covers.[3]
Distribution and habitat
Kew's distribution records list native occurrences from southern Mexico through Central America to Panama, including Belize, Guatemala, El Salvador, Honduras, Nicaragua and Costa Rica. Its country-level table treats Colombia as introduced, although its brief range summary includes Colombia. The older taxonomic factsheet also documents Colombian specimens; the occurrence and its native status should therefore be distinguished.[1][3]
The species grows in open scrub, pastures, abandoned fields, roadsides and rocky places. It can be abundant during the early stages of vegetation regrowth and occurs in both relatively dry and wetter settings.[3]
Ant partners
The tree supplies ants with sugary nectar from glands outside its flowers and small, nutrient-rich structures on the leaflets called Beltian bodies. The hollow thorns provide nest chambers. One well-studied partner is Pseudomyrmex spinicola. Its workers defend their host and can remove competing vegetation nearby.[2]
These structures are not fully developed when the seedling first emerges. In controlled growth experiments, V. collinsii and a related ant-acacia developed enlarged nectar glands, swollen thorns and Beltian bodies in a sequence after germination. A 2019 study linked this developmental change to age-related changes in gene regulation. Reduced light delayed the development of the structures in the experimental plants.[4]
Herbivores and defence
Ant protection does not exclude every plant-feeding insect. The sap-feeding bug Piezogaster reclusus can feed on young leaves despite the resident ants. Experiments published in 2014 found that chemicals on the bug's outer surface helped it avoid attack. Bugs moved between ant colonies were attacked more often, supporting the explanation that their chemical disguise is associated with the particular colony or host plant.[2]
Botanical names
Kew accepts Vachellia collinsii and records the combination as published in a journal volume dated 2005 but issued in 2006. It treats Acacia costaricensis, described in 1913, as a synonym of the same species.[1]
References
- ↑ 1.0 1.1 1.2 Royal Botanic Gardens, Kew. “Vachellia collinsii”. Plants of the World Online. Accessed 9 October 2026.
- ↑ 2.0 2.1 2.2 Whitehead, S. R., and colleagues (2014). “A Specialist Herbivore Uses Chemical Camouflage to Overcome the Defenses of an Ant-Plant Mutualism”. PLOS ONE 9(7): e102604. doi:10.1371/journal.pone.0102604. Accessed 9 October 2026.
- ↑ 3.0 3.1 3.2 3.3 Centre for Plant Biodiversity Research. “Vachellia collinsii”: taxonomic factsheet, drawing on Seigler and Ebinger and Janzen. Accessed 9 October 2026.
- ↑ Leichty, A. R.; Poethig, R. S. (2019). “Development and evolution of age-dependent defenses in ant-acacias”. PNAS 116(31): 15596–15601. doi:10.1073/pnas.1900644116. Accessed 9 October 2026.