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Contrasting seasonal niche separation between rare and abundant taxa conceals the extent of protist diversity.

ABSTRACT: With the advent of molecular methods, it became clear that microbial biodiversity had been vastly underestimated. Since then, species abundance patterns were determined for several environments, but temporal changes in species composition were not studied to the same level of resolution. Using massively parallel sequencing on the 454 GS FLX platform we identified a highly dynamic turnover of the seasonal abundance of protists in the Austrian lake Fuschlsee. We show that seasonal abundance patterns of protists closely match their biogeographic distribution. The stable predominance of few highly abundant taxa, which previously led to the suggestion of a low global protist species richness, is contrasted by a highly dynamic turnover of rare species. We suggest that differential seasonality of rare and abundant protist taxa explains the--so far--conflicting evidence in the 'everything is everywhere' dispute. Consequently temporal sampling is basic for adequate diversity and species richness estimates.

SUBMITTER: Nolte V

PROVIDER: S-EPMC2916215 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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Contrasting seasonal niche separation between rare and abundant taxa conceals the extent of protist diversity.

Nolte Viola V Pandey Ram Vinay RV Jost Steffen S Medinger Ralph R Ottenwälder Birgit B Boenigk Jens J Schlötterer Christian C

Molecular ecology 20100701 14

With the advent of molecular methods, it became clear that microbial biodiversity had been vastly underestimated. Since then, species abundance patterns were determined for several environments, but temporal changes in species composition were not studied to the same level of resolution. Using massively parallel sequencing on the 454 GS FLX platform we identified a highly dynamic turnover of the seasonal abundance of protists in the Austrian lake Fuschlsee. We show that seasonal abundance patter ...[more]

PMID: 20609083

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Project description:Global climate change has emerged as a critical environmental problem. Different types of climate extremes drive soil microbial communities to alternative states, leading to a series of consequences for soil microbial ecosystems and related functions. An effective method is urgently needed for buffering microbial communities to tackle environmental disturbances. Here, we conducted a series of mesocosm experiments in which the organic (NOF) and chemical fertilizer (NCF) long-term-amended soil microbiotas were subjected to environmental disturbances that included drought, flooding, freeze-thaw cycles, and heat. We subsequently tracked the temporal dynamics of rare and abundant bacterial taxa in NOF and NCF treatment soils to assess the efficiencies of organic amendments in recovery of soil microbiome. Our results revealed that freeze-thaw cycles and drought treatments showed weaker effects on bacterial communities than flooding and heat. The turnover between rare and abundant taxa occurred in postdisturbance succession of flooding and heat treatments, indicating that new equilibria were tightly related to the rare taxa in both NCF and NOF treatment soils. The Bayesian fits of modeling for the microbiome recovery process revealed that the stability of abundant taxa in NOF was higher than that in NCF soil. In particular, the NOF treatment soil reduced the divergence from the initial bacterial community after weak perturbations occurred. Together, we demonstrated that long-term organic input is an effective strategy to enhance the thresholds for transition to alternative states via enhancing the stability of abundant bacterial species. These findings provide a basis for the sustainable development of agricultural ecosystems in response to changing climates. IMPORTANCE Different climate extremes are expected to be a major threat to crop production, and the soil microbiome has been known to play a crucial role in agricultural ecosystems. In recent years, we have known that organic amendments are an effective method for optimizing the composition and functioning of the soil microbial community and maintaining the health of the soil ecosystem. However, the effects of organic fertilization on buffering bacterial communities against environmental disturbances and the underlying mechanisms are still unclear. We conducted a series of mesocosm experiments and showed that organic fertilizers had additional capacities in promoting the soil microbiome to withstand climate change effects. Our study provides both mechanistic insights as well as a direct guide for the sustainable development of agricultural ecosystems in response to climate change.

Project description:BackgroundOur knowledge of the phylogeny and diversity of aquatic protists is rapidly increasing due to molecular surveys and next-generation sequencing approaches. This has led to a considerable discrepancy between the taxa known from cultures and those known from environmental 18S rRNA gene sequences. Hence, it is generally difficult to assign ecological functions to new taxa detected by culture-independent molecular approaches.Methodology/principal findingsA combination of unamended dark incubations and 18S rRNA sequencing was chosen to link molecular diversity data of uncultured protists with heterotrophic, presumably bacterivorous, growth. The incubations, conducted with Baltic Sea brackish water, resulted in a consistent shift from a protistan community dominated by phototrophs to one in which heterotrophs predominated. This was determined on the basis of cell abundance and 18S rRNA sequences derived from fingerprint analysis and clone libraries. The bulk of enriched phylotypes after incubation were related to hitherto uncultured marine taxa within chrysophytes, ochrophytes, choanoflagellates, cercozoans, and picobiliphytes, mostly represented in recently established or here defined environmental clades. Their growth in the dark, together with coinciding results from studies with a similar objective, provides evidence that these uncultured taxa represent heterotrophic or mixotrophic species.Conclusions/significanceThese findings shed some light into the trophic role of diverse uncultured protists especially within functionally heterogeneous groups (e.g., chrysophytes, ochrophytes) and groups that appear to be puzzling with regard to their nutrition (picobiliphytes). Additionally, our results indicate that the heterotrophic flagellate community in the southwestern Baltic Sea is dominated by species of marine origin. The combination of unamended incubations with molecular diversity analysis is thus confirmed as a promising approach to explore the trophic mode of environmentally relevant protist taxa for which only sequence data are currently available.

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Contrasting seasonal niche separation between rare and abundant taxa conceals the extent of protist diversity.

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Contrasting seasonal niche separation between rare and abundant taxa conceals the extent of protist diversity.

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