Complexity and contingency frame much of current thinking in population and community ecology. The coffee pest, Leucoptera coffeella, is particularly problematical in Puerto Rico, but is usually held under control in Mexico. A variety of arboreal ants are effective predators in Mexico, but are limited in an indirect fashion by the common aggressive arboreal ant, Azteca sericeasur. In Puerto Rico this species does not occur, suggesting that the small arboreal ants might be more effective predators there than in Mexico. However, the contingency of large population densities of Anoline lizards is well-known as a major biological control force for the leaf miner. Ants, especially the non-native Wasmannia auropunctata, have a negative effect on the lizards. Surveying ants and coffee leaf miners in 25 coffee farms in Puerto Rico, we investigate the effect of ants, in particular W. auropunctata, on the coffee leaf miner, and find that this ant species has a positive relationship with the miner. In a more detailed spatial study of two farms, surveys of anoline lizards show no significant negative relationship between the lizards and W. auropunctata on a per plant basis. However, we found a significantly lower abundance of lizards on patches dominated by this ant, suggesting that W. auropunctata indirectly protects the coffee leaf miner against this potential lizard predator. Thus, the structural complexity of a trait-mediated indirect effect occurs both in Mexico and Puerto Rico and potentially limits the effectiveness of biological control elements, but the contingencies are distinct in the two sites.
November 13, 2020