Microbial eukaryote plankton communities of high‐mountain lakes from three continents exhibit strong biogeographic patterns

Abstract

Microbial eukaryotes hold a key role in aquatic ecosystem functioning. Yet, their diversity in freshwater lakes, particularly in high-mountain lakes, is relatively unknown compared with the marine environment. Low nutrient availability, low water temperature and high ultraviolet radiation make most high-mountain lakes extremely challenging habitats for life and require specific molecular and physiological adaptations. We therefore expected that these ecosystems support a plankton diversity that differs notably from other freshwater lakes. In addition, we hypothesized that the communities under study exhibit geographic structuring. Our rationale was that geographic dispersal of small-sized eukaryotes in high-mountain lakes over continental distances seems difficult. We analysed hypervariable V4 fragments of the SSU rRNA gene to compare the genetic microbial eukaryote diversity in high-mountain lakes located in the European Alps, the Chilean Altiplano and the Ethiopian Bale Mountains. Microbial eukaryotes were not globally distributed corroborating patterns found for bacteria, multicellular animals and plants. Instead, the plankton community composition emerged as a highly specific fingerprint of a geographic region even on higher taxonomic levels. The intraregional heterogeneity of the investigated lakes was mirrored in shifts in microbial eukaryote community structure, which, however, was much less pronounced compared with interregional beta-diversity. Statistical analyses revealed that on a regional scale, environmental factors are strong predictors for plankton community structures in high-mountain lakes. While on long-distance scales (>10 000 km), isolation by distance is the most plausible scenario, on intermediate scales (up to 6000 km), both contemporary environmental factors and historical contingencies interact to shift plankton community structures.

Geographic distance and mountain ranges structure freshwater protist communities on a European scalе

“…In fact, we found a low taxon overlap between lakes and a correspondingly high contribution to beta-diversity of individual habitats. In accordance with our findings, a large genetic divergence between distinct lake microbial communities has been reported in recent deep-sequencing campaigns, in particular for the rare biosphere (Filker et al 2016, Grossmann et al 2016b, Triadó-Margarit and Casamayor 2012. In particular, distribution patterns of rare taxa seem to vary widely and to deviate from the rather uniform patterns in abundant protists (Grossmann et al 2016a, Schiaffino et al 2016).…”

“…Considerable research effort has been focused on marine diversity (Countway et al 2005,Countway et al 2007, Campo et al 2016, Lovejoy et al 2006, López-García et al 2001, Massana and Pedrós-Alió 2008, Worden et al 2006. Despite the global importance of freshwater resources and the heterogeneity of freshwater systems, their biological diversity has been comparatively neglected (Filker et al 2016, Grossmann et al 2016a, Kammerlander et al 2015, Lepère et al 2007, Taib et al 2013, Triadó-Margarit and Casamayor 2012, Slapeta et al 2005. Our study revealed a high diversity of microbial freshwater eukaryotes and a high level of regional separation.…”

“…Most, if not all, microbial ecologists meanwhile agree that at least some single-celled organisms have limited distribution patterns (Filker et al 2016, Kammerlander et al 2015, van der Gast 2014, Wu et al 2009) and that on a larger scale, historical and geographic factors may also affect protist distribution and dispersal (Filker et al 2016, Izaguirre et al 2015. However, despite indications of large-scale variation between protist communities, geographical factors are considered to be of minor importance at short to intermediate distances (Beisner et al 2006, Filker et al 2016.…”

“…However, despite indications of large-scale variation between protist communities, geographical factors are considered to be of minor importance at short to intermediate distances (Beisner et al 2006, Filker et al 2016. If this turns out to be true, protist distribution patterns would clearly deviate from those of macroorgansims, in particular in Europe due to the recent geological past of this continent: In the quarternary, Europe underwent several cycles of glaciations which strongly structured biological communities -at least of macroorganisms.…”

Novel Diversity of Deeply Branching Holomycota and Unicellular Holozoans Revealed by Metabarcoding in Middle Paraná River, Argentina

“…For example, mountain lakes have been shown to harbor an extensive diversity within large eukaryotic lineages and a high proportion of unclassified sequences (Triadó-Margarit and Casamayor, 2012;Kammerlander et al, 2015;Filker et al, 2016;Boenigk et al, 2018). This is remarkable given the extreme oligotrophic condition of some of these lakes.…”