Gastrointestinal Microbial Community Composition and Habitat Structure in Howler Monkeys (Alouatta pigra)

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Howler monkeys (Alouatta sp.) are among the most folivorous of the New World monkeys and have highly flexible diets.  However, despite the fact that groups of howlers exhibit distinct diets depending on spatial and temporal patterns of resource availability, activity patterns are consistent across howler groups and species.

High levels of fiber and toxins in leaves make gut microbial fermentative activity essential to howler nutrition, and based on studies with other mammals, it is possible that differences in gut microbial community composition allow groups of howlers in different habitats to take advantage of distinct resources to fuel the same activities.

To investigate variation in gut microbial community composition within a species, we collected fecal samples from five groups of black howler monkeys (Alouatta pigra) in Mexico over an eight-week period (May-July 2009). Two of these groups inhabited a continuous, tall rainforest. The other three inhabited a fragmented, tall rainforest; a continuous, semi-deciduous seasonal forest; and a rehabilitation center.

Following the isolation and purification of microbial DNA from all samples, we used community fingerprinting (ARISA) and high-throughput sequencing of the 16s ribosomal RNA gene (V1-V3) to describe the microbial community structure in each group. Our sequencing resulted in >2.6 million reads from 33 individuals, giving us unprecedented sequencing depth.

Preliminary analyses indicate that differences in gut microbial community composition are related to the environment each group inhabits. Basic ecological data suggest that these differences are a result of diet composition. Differences in host monkey microbial communities may have important implications for primate adaptation, evolution, and conservation.

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This project was funded through National Science Foundation (NSF) grant #0935347.