Host specificity of parasite manipulation: Zombie ant death location in Thailand vs. Brazil

Abstract

Recently we presented how Camponotus ants in Thailand infected with the fungus Ophiocordyceps unilateralis are behaviorally manipulated into dying where the conditions are optimal for fungal development. Death incurred in a very narrow zone of space and here we compare this highly specific manipulation with a related system in Brazil. We show that the behavioral manipulation is less fine-tuned and discuss the potential explanations for this by examining differences in ant host and environmental characteristics.

Keywords: Parasite manipulation; host specificity; zombie ants.

Figure 1. The height above ground of dead infected ants. (A) shows that there were no significant differences between the height of dead ants in four different life stages in Brazil (fresh, stroma, mature and hyperparasitized (HP); mean height cm ± SD). The death height therefore does not affect which parasites reach maturity and which succumb to hyperparasitic fungi. (B) shows the difference between the height at which dead infected ants are found in Brazil and Thailand, where the ants die at a greater height in Brazil with a greater variance around the mean (mean height cm ± SD).

Figure 2. The direction of the heads of dead infected ants in Brazil and Thailand. In Brazil there was no pattern in the direction while the dead ants pointed toward South in Thailand. The blue slices show the number of dead ants in a given direction while the red lines indicate the mean head direction and the 95% confidence interval.