Sequencher path bio upenn drivers#

Geographic distance contributed the largest partial regression coefficient ( b = 0.40, P < 0.0001), with sediment moisture, nitrate concentration, plant cover, salinity, and air and water temperature contributing to smaller, but significant, partial regression coefficients ( b = 0.09вЂ“0.17, P < 0.05) ( Table 1). Over all scales, the MRM model explained a large and significant proportion ( R 2 = 46% P < 0.0001) of the variability in Nitrosomonadales community similarity. The partial regression coefficients of an MRM model give a measure of the rate of change in community similarity per standardized unit of similarity for the variable of interest all other explanatory variables are held constant ( 22). To further identify the relative importance of factors contributing to these correlations, we used a multiple regression on matrices (MRM). This approach constrained the pool of total diversity (richness) and kept the environmental and plant variation relatively constant, increasing our ability to identify if dispersal limitation influences AOB composition. We limited our sampling to a monophyletic group of bacteria, the AOB within the ОІ-Proteobacteria, and one habitat, salt marshes primarily dominated by cordgrass ( Spartina spp.). A partially nested sampling design achieved a relatively balanced distribution of pairwise distance classes over nine orders of magnitude, from 3 cm to 12,500 km ( Fig. We compared AOB community composition in 106 sediment samples from 12 salt marshes on three continents. We chose to focus on the ammonia-oxidizing bacteria (AOB), which along with the ammonia-oxidizing archaea ( 14), perform the rate-limiting step of nitrification and thus play a key role in nitrogen dynamics. Here we investigate whether the mechanisms underlying ОІ-diversity in bacteria also vary by spatial scale. These results highlight the importance of considering multiple spatial scales for understanding microbial biogeography. Our data are consistent with the idea that dispersal limitation at local scales can contribute to ОІ-diversity, even though the 16S rRNA genes of the relatively common taxa are globally distributed. In contrast to macroorganism studies, however, we found no evidence of evolutionary diversification of ammonia-oxidizing bacteria taxa at the continental scale, despite an overall relationship between geographic distance and community similarity.

Sequencher path bio upenn drivers#

As observed in studies of macroorganisms, the drivers of salt marsh bacterial ОІ-diversity depend on spatial scale. Here we tested whether the mechanisms that underlie bacterial ОІ-diversity vary over centimeters to continental spatial scales by comparing the composition of ammonia-oxidizing bacteria communities in salt marsh sediments.

The factors driving ОІ-diversity (variation in community composition) yield insights into the maintenance of biodiversity on the planet.