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

Abstract

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 longterm survival of spore-forming Firmicute pathogens and thus may limit the role that vultures play as potential disease vectors.

Abiotic stress tolerance and competition‐related traits underlie phylogenetic clustering in soil bacterial communities

“…Proteobacteria dominated both environments as is common for soils worldwide (Janssen 2006), but were significantly overrepresented in patches with their high resource availability. This correlates well with the observation that Proteobacterial abundance increases with total organic carbon from the local to the global scales (Fierer et al 2007;Ganz et al 2012). Furthermore, the overrepresentation of Proteobacteria in carbon-rich soils was associated with the underrepresentation of four major phyla (Fig.…”

“…Soil bacterial communities were phylogenetically clustered, as has been repeatedly reported in the literature across biomes (Horner-Devine & Bohannan 2006;Bryant et al 2008;Costello et al 2009;Chong et al 2012;Ganz et al 2012). Using a trait-based approach, here we provide evidence supporting that phylogenetic clustering in soil bacteria can arise from the environmental selection of conserved functional traits either conferring tolerance to environmental stress or competitive abilities.…”

“…This observation relates to the notion that soil bacteria typically co-occur with evolutionarily related organisms more often than expected by chance, a process that results in phylogenetic clustering (Horner-Devine & Bohannan 2006;Bryant et al 2008). Based on classical community phylogenetics, such clustered patterns have been assigned to the environmental selection of taxa sharing conserved traits that allow them to surpass an abiotic filter (Webb et al 2002;Horner-Devine & Bohannan 2006;Costello et al 2009;Ganz et al 2012). Under this traditional framework, biotic interactionsmainly competition, the other major force driving community assemblylead to the co-existence of phylogenetically distant organisms and hence create overdispersed patterns.…”

Spores and soil from six sides: interdisciplinarity and the environmental biology of anthrax (Bacillus anthracis)

“…Previous theory had suggested that white‐backed vultures ( Gyps africanus ) and lappet‐faced vultures ( Torgos tracheliotos ) might disperse bacteria from carcass sites to their nesting sites and thereby help spread disease, based on anecdotal evidence (Bullock, ), examination of faeces and contaminated water (Lindeque & Turnbull, ; Hugh‐Jones & De Vos, ), and experimental work on anthrax spore passage through vulture digestive tracts (Urbain & Novel, ; Houston & Cooper, ). However, research in Etosha failed to find higher B. anthracis concentrations at vulture nests, perhaps because vultures' acidic droppings produce soil unsuitable for anthrax spores (Ganz et al ., ). Furthermore, during the first 72 h after carcass deposition, if a carcass remains unopened, vegetative cells fail to sporulate, ending the life cycle (Davies, ; Lindeque & Turnbull, ; Hugh‐Jones & De Vos, ).…”

Diversity and Function of Bacterial Assemblages in Savanna Vegetation Soils

“…Although several papers did not describe these parameters, where reported these values were similar across the analyzed sites (protected or modified), indicating a predominance of clayey soils (Table 6.3). the median values of the included studies (Pinto et al 2006;Carvalho et al 2007;Quirino et al 2009;Bresolin et al 2010;Frazão et al 2010;Peixoto et al 2010;Viana et al 2011;Araujo et al 2012;Ganz et al 2012;Mendes et al 2012;Vinhal-Freitas et al 2013;Rachid et al 2013;Rampelotto et al 2013;Rossi et al 2013;Souza et al 2013 …”