Differential Abundance of Microbial Functional Groups along the Elevation Gradient from the Luquillo Mountains to the Coast

TitleDifferential Abundance of Microbial Functional Groups along the Elevation Gradient from the Luquillo Mountains to the Coast
Publication TypeJournal Article
Year of Publication2012
AuthorsCantrell, SA, Lodge, DJ, Cruz, V, Garcia, LM, Perez-Jimenez, JR, Molina, M
JournalEcological Bulletins
IssueElevation Gradient in the Luquillo Mountains of Puerto Rico (2012)
Accession NumberLUQ.1051
Other Numbers1051
Keywordsabundance, basidiomycete fungi, nitrogen-fixing activity

Microbial communities respond to multiple abiotic and biotic factors that change along elevation gradients. We compare changes in microbial community composition in soil and review previous research on differential abundance of microbial functional groups along an elevation gradient in eastern Puerto Rico. Previous studies within the Luquillo Mountains showed that activity of methanogenic bacteria increased significantly with elevation, whereas diversity, abundance or activity decreased with elevation in 'slime molds', microbial nitrogen-fixing activity (nitrogenase), and abundance of basidiomycete fungi that degrade lignin in leaf litter. Our results, based on fatty acid (FA) composition and TRFLP analyses from a longer gradient (dry coastal forest to elfin rainforest) produced humped distributions for Shannon diversity of FA, fungal to bacteria (F:B) ratios, fungi, Myxomycetes, G- FA cy19:0 and sulfate reducing bacteria (SRB) 10Me18:0. Soil microbial communities differed significantly among forest types using ANCOVA. TRFLP were more frequently unique to forest types in fungi than bacteria, but we found unique and diverse sulfidogenic and crenarchaeal assemblages in some forest types, with highest diversity in high elevation palm and elfin forests. In multiple linear regression (MLR) models, soil moisture was predictive for all but Actinomycete FA abundance, and forest type contributed significantly to these same models for F:B ratios and all FA fractions except for G- SRB 10Me18:0, and G+ bacteria 15:0. F:B ratio peaked at mid-elevation, then declined with increasing moisture at higher elevation. Since most G- and G+ bacterial FA were positively related to soil pH in MLR models, lower pH in mid-elevation tabonuco forest soil may suppress bacteria and contribute to higher F:B ratios in this forest type.