Diversity and structure of soil bacterial communities associated with vultures in an African savanna

Abstract

Bird guano has been shown to alter the structure and function of ecological communities. Here we characterize the effects of vulture guano on the phylogenetic structure, taxa richness, and abundance in soil bacterial communities within an African savanna. By altering soil chemistry and nutrient status, vulture guano appears to play a role in influencing the structure of soil bacterial communities. DNA was extracted from soil collected under twenty trees: five African white‐backed vulture (Gyps africanus, WBV) nesting sites, five lappet‐faced vulture (Torgos tracheliotos, LFV) nesting sites and ten control sites where no sign of vulture activity was detected. Using a high‐density phylogenetic microarray (PhyloChip G2), we identified 1,803 bacterial Operational Taxonomic Units (OTUs) in the twenty samples. Analysis of beta‐diversity using the Unifrac distance metric demonstrated that WBV nesting sites were phylogenetically distinct from both control trees and LFV nesting sites. We detected a higher degree of phylogenetic clustering in soil bacterial communities associated with both WBV and LFV nesting sites compared to control sites, suggesting that the deposition of guano increases the strength of habitat filtering in these communities. Canonical correspondence analysis revealed that variation in OTU intensity (a measure of relative abundance) could be related to variations in pH, electrical conductivity and total nitrogen content. WBV sites explained 10% to 22% of the variation in OTU intensity. The elevated total nitrogen and lower pH characteristic of soils associated with vultures may favor Proteobacteria and suppress Firmicutes, particularly Clostridia and Bacilli. Acidic aggregations of vulture guano may be unlikely to support long‐term survival of spore‐forming Firmicute pathogens and thus may limit the role that vultures play as potential disease vectors.