Vachellia Collinsii: Assessing the Below-Ground Dynamics in an Ant-Plant Relationship (UROP)

Abstract

The mutualistic interaction between the bullhorn acacia (Vachellia collinsii) and its resident ants (Pseudomyrmex) is well-documented for its above-ground dynamics, where the plant provides food and shelter to the ants in exchange for protection and vegetation clearance. This study explores the under-studied below-ground impacts of this mutualism, hypothesizing that the ants’ above-ground clearing activities affect fine root mass beneath V. collinsii canopies. Conducted in June 2024 at Estacion Experimental Horizontes in the tropical dry forest of northwestern Costa Rica, this study compares fine root mass within V. collinsii clearings to that in adjacent control sites without V. collinsii. Fine root samples were collected from six cores per site in ten experimental sites. Statistical analyses revealed no significant difference in fine root mass between V. collinsii and control sites (p = 0.246). However, a significant positive relationship was found between clearing size and the difference in root mass (R² = 0.64, p = 0.013), suggesting that larger clearings are associated with greater differences in fine root mass. These results indicate that while V. collinsii clearings do impact below-ground dynamics, the effects are more pronounced with larger clearing sizes.