Monday, August 2, 2010 - 1:50 PM

COS 4-2: Investigating trophic interactions with molecular methods: Insectivory by bats in the coffee agroecosystem

Kimberly Williams-Guillén, University of Washington and Ivette Perfecto, University of Michigan.

Although bats are diverse and abundant vertebrate insectivores, their role in controlling arthropods has been overlooked.  Bats may have similar impacts on agricultural pests as those attributed to birds; however, their cryptic habits have impeded studies of their diets.  To determine if bats consume arthropod crop pests in a tropical agroecosystem, we applied molecular techniques amplify and identify insect DNA sequences from bat fecal samples.  Between November 2006 and July 2008, we collected fecal samples from 240 insectivorous bats captured in coffee plantations and forest fragments in the Soconusco region of Chiapas, Mexico.  We extracted insect DNA from fecal samples and then tested for the presence of DNA from arthropod pests of coffee (coffee berry borer: Hypothenemus hampei; and a tettigonid pest known locally as “chacuatete,” Idiarthron subquadratum) by conducting a PCR reaction using a series of species-specific primers for a portion of the mitochondrial COI gene.  

Of the 124 samples screened to date, 5 tested positive for coffee berry borer, and 7 for the tettigonid pest.  All positives have come either from a foliage-gleaning insectivorous bat (Micronycteris mictrotis) or from an aerial-hawking insectivore (Pteronotus parnelli) whose specialized echolocation behavior that facilitates foraging in high-clutter habitats.  Both these bat species have wing morphologies that allow highly maneuverable flight through dense vegetation.  We suggest that because the coffee berry borer and chacuatete are infrequent fliers, they are vulnerable to predation by bats that are able to take these insects when they are close to, or directly on, coffee plants.  All bats that tested positive for coffee berry borer and chacuatete were captured in diverse shade coffee plantations with well-developed tree canopies, or in small forest fragments adjacent to shade coffee; none of the bats captured in low-shade coffee monocultures tested positive for consumption of these two insect pests, even though both are known to occur in plantations throughout the region.  Because insectivorous bats are more abundant in the more biodiverse, high-shade coffee plantations, these areas may benefit more from bat predation on coffee pests.  We are currently developing species specific primers for a number of additional insect pests of coffee, including the coffee leaf miner (Leucoptera coffeella); the brown coffee twig beetle (Xylosandrus morigerus); and a chrysomelid known locally as the “tortuguilla” (Rhabdopterus jansoni).  Results from screening for these pests will also be discussed in the context of bat foraging adaptations and intensity of agricultural management.