Assessment of Wasmannia auropunctata invasion in three habitat types at Las Cruces Biological Station

The Little Fire Ant, Wasmannia auropunctata is an invasive species,inhabiting disturbed habitats, thriving, and negatively affecting forest biodiversity. Two previous studies have been done on presence of ant species at the Las Cruces Biological Station, Coto Brus, Costa Rica, neither which focused on W. auropunctata ant densities. it is of interest to ascertain 1) if there was a difference between populations of W. auropunctata in a disturbed area, Melissa’s Meadow, and that of the primary forest, 2) if there were trends between ant densities as a function of distance between the border of the 2 habitats, and 3) if W. auropunctata was spreading from the meadow into the adjacent primary forest. 27 samples of ants were collected along three transects starting in Melissa’s Meadow and ending in the adjacent primary forest, Five samples were also taken in an abandoned pastureland to establish presence of W. auropunctata. Sample area was measured to determine ants per unit area. It was concluded that populations of W. auropunctata were significantly different in Melissa’s Meadow and primary forest, no difference was found between the two habitats and the meadow/forest interface. The five additional samples showed presence of W. auropunctata in the pastureland, so it can be assumed that W. auropunctata was present in the area prior to reforestation efforts in Melissa’s Meadow, and not introduced through human import. It is probable that the diversity of other ant species and arthropods in the primary forest are preventing W. auropunctata from flourishing across the interface.