Distinct gut bacterial communities across wild Trinidadian guppy populations

Background/Question/Methods

Prokaryotic organisms can have complex relationships with their eukaryotic hosts, which can, in turn, impact their ecology and evolution. We are studying the interplay among gut bacteria and diet within the Trinidadian guppy, Poecilia reticulata. Guppies from stream habitats with higher predation pressure exhibit faster growth rates and consume more invertebrates but fewer diatoms and detritus than guppies from low predation habitats. We hypothesize that there is a characteristic high- (HP) and low-predation (LP) guppy microbial community. Such a finding would implicate the gut microbiome as a potential source of genetic variation that could help shape the evolution of life histories and digestive physiology within guppies. To better understand the variation in natural guppy gut communities, we have utilized next generation, 454 pyrosequencing to analyze the gut bacteria of guppies from high and low predation environments from four different streams. We used the Qiime pipeline to analyze bacterial communities within guppy guts. We assigned taxonomic identities to the 454 pyrosequencing reads, grouped sequences into OTUs and constructed a phylogenetic tree, which was used calculate beta diversity using unweighted UniFrac and then compared using principal coordinate analysis.

Results/Conclusions

Proteobacteria dominated most guppy libraries, but Fusobacteria were particularly abundant bacteria in most individuals from one stream. Principal coordinate analyses showed that stream had a significant effect in shaping guppy microbial communities. Predation level appeared to moderately effect gut microbes and the interaction of stream and predation level was found to be significant. This research also revealed inter-individual gut microbial community variation among fish at a deep-sequencing level. Overall, there is marked similarity of communities between individuals from the same streams and the same sites. In light of the differences in bacterial communities between streams and predation levels, this finding suggests a functional and, potentially, adaptive significance of gut bacteria in diet and life history evolution. Organisms’ abilities to acquire energy from their surroundings are essential to their growth, reproduction and survival and have a significant impact on the evolutionary trajectories of populations. Given the known roles of gut bacteria in energy extraction and the variation in gut communities across host diets, they may have a significant role in the ecology and evolution of fish species.