Regional and global elevational patterns of microbial species richness and evenness

Abstract

Although elevational gradients in microbial biodiversity have attracted increasing attention recently, the generality in the patterns and underlying mechanisms are still poorly resolved. Further, previous studies focused mostly on species richness, while left understudied evenness, another important aspect of biodiversity. Here, we studied the elevational patterns in species richness and evenness of stream biofilm bacteria and diatoms in six mountains in Asia and Europe. We also reviewed published results for elevational richness patterns for soil and stream microbes in a literature analysis. Our results revealed that even within the same ecosystem type (that is, stream) or geographical region, bacteria and diatoms showed contrasting patterns in diversity. Stream microbes, including present stream data, tend to show significantly increasing or decreasing elevational patterns in richness, contrasting the findings for soil microbes that typically showed nonsignificant or significantly decreasing patterns. In all six mountains for bacteria and in four mountains for diatoms, species richness and evenness were positively correlated. The variation in bacteria and diatom richness and evenness were substantially explained by anthropogenic driven factors, such as total phosphorus (TP). However, diatom richness and evenness were also related to different main drivers as richness was mostly related to pH, while evenness was most explained by TP. Our results highlight the lack of consistent elevational biodiversity patterns of microbes and further indicate that the two facets of biodiversity may respond differently to environmental gradients.

Nutrient enrichment modifies temperature-biodiversity relationships in large-scale field experiments

“…), and in a subtropical region, Laojun Mountain in China (2,280–3,820 m a.s.l. )28, in July and September–October 2013, respectively (Fig. 1a).…”

“…Sediment Chl a was extracted with 90% acetone49. Sediment genomic DNA was extracted using the phenol chloroform method, and bacterial 16S rRNA genes were amplified in triplicate using universal bacterial primers28. Real-time qPCR quantification of bacterial 16S rRNA genes was performed on an iCycler iQ5 thermocycler (Bio-Rad, Hercules, CA) as described previously60.…”

“…PCR products were sequenced with MiSeq (Illumina, San Diego, CA). The sequences were processed in QIIME (v1.8)2861. OTUs were defined at 97% sequence similarity.…”

“…Bacterial communities allow us to examine patterns of diversity with a high degree of experimental control and replication in natural field conditions that are subject to real species pool effects, experiments that cannot be conducted under laboratory conditions or with larger organisms within feasible time periods2627. Moreover, our recent field survey on the study mountains indicated that nutrients were one of the main drivers of aquatic bacterial diversity28.…”

Towards a Microbial Conservation Perspective in High Mountain Lakes

“…Again, the higher than expected habitat richness provides a rich background for diverse planktonic bacterial communities. Bacteria are also highly abundant and diverse in the epilithic biofilms of streams and lakes, although no consistent global elevational patterns in biodiversity for stream bacteria exist (Wang et al 2017). These biofilms play, however, a relevant and specific biogeochemical role in mountain lakes (Vila-Costa et al 2014).…”