Abstract
Bacteria are vital components of lake systems, driving a variety of biogeochemical cycles and ecosystem services. Bacterial communities have been shown to have a skewed distribution with a few abundant species and a large number of rare species. The contribution of environmental processes or geographic distance in structuring these components is uncertain. The discrete nature of lakes provides an ideal test case to investigate microbial biogeographical patterns. In the present study, we used 16S rRNA gene metabarcoding to examine the distribution patterns on local and regional scales of abundant and rare planktonic bacteria across 167 New Zealand lakes covering broad environmental gradients. Only a few amplicon sequence variants (ASVs) were abundant with a higher proportion of rare ASVs. The proportion of locally abundant ASVs was negatively correlated with the percentage of high productivity grassland in the catchment and positively with altitude. Regionally rare ASVs had a restricted distribution and were only found in one or a few lakes. In general, regionally abundant ASVs had higher occupancy rates, although there were some with restricted occupancy. Environmental processes made a higher contribution to structuring the regionally abundant community, while geographic distances were more important for regionally rare ASVs. A better understanding of the processes structuring the abundance and distribution of bacterial communities within lakes will assist in understand microbial biogeography and in predicting how these communities might shift with environmental change.
Highlights
Many ecological studies have overarching goals to understand the biodiversity and spatial distribution of organisms and to determine the drivers underlying these patterns
When the data from all lakes were combined, bacterioplankton were predominantly comprised of Gammaproteobacteria, Actinobacteria (20.9 ± 10.8%), Bacteroidia (14.8 ± 8.8%), Alphaproteobacteria (12.3 ± 7.9%), and Verrucomicrobiae (9.7 ± 6.4%) (Supplementary Figure 2 and Supplementary Table 2)
Our results indicated that the regionally abundant and rare components of the bacterial community were structured differently with environmental processes having a greater impact on the abundant community, while geographic distance and environmental processes contributed for the rare component
Summary
Many ecological studies have overarching goals to understand the biodiversity and spatial distribution (biogeography) of organisms and to determine the drivers underlying these patterns. It has been postulated that local environmental processes and geographic distances (dispersal related) factors are potential mechanisms in structuring microbial biogeography (Liu et al, 2019; Sadeghi et al, 2021). Environmental processes include abiotic (e.g., nutrients) and biotic (e.g., predation and competition) factors that regulate the community structure (Zhou and Ning, 2017). Neutral processes suggest that all taxa are functionally equivalent and not strongly affected by environmental effects and that community assembly is driven by variations in dispersal coupled with ecological drift (Hubbell, 2001; Barberán et al, 2014a; Zhou and Ning, 2017). There is compelling research which suggests that neither process is dominant in regulating microbial distribution patterns in lakes (Langenheder and Ragnarsson, 2007; Langenheder and Székely, 2011; Liu et al, 2015)
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