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Insights into global planktonic diatom diversity: The importance of comparisons between phylogenetically equivalent units that account for time


Metabarcoding has offered unprecedented insights into microbial diversity. In many studies, short DNA sequences are binned into consecutively lower Linnaean ranks, and ranked groups (e.g., genera) are the units of biodiversity analyses. These analyses assume that Linnaean ranks are biologically meaningful and that identically ranked groups are comparable. We used a metabarcode dataset for marine planktonic diatoms to illustrate the limits of this approach. We found that the 20 most abundant marine planktonic diatom genera ranged in age from 4 to 134 million years, indicating the non-equivalence of genera because some have had more time to diversify than others. However, species richness was largely independent of genus age, suggesting that disparities in species richness among genera were better explained by variation in rates of speciation and extinction. Taxonomic classifications often do not reflect phylogeny, so genus-level analyses can include phylogenetically nested genera, further confounding rank-based analyses. These results underscore the indispensable role of phylogeny in understanding patterns of microbial diversity.

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Subject categories: Microbial ecology and functional diversity of natural habitats

Integrated genomics and post-genomics approaches in microbial ecologyReferences have been reordered. Please check.OK.


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This work was supported by a grant from the Simons Foundation (403249, AJA). This material is also based upon work supported by the National Science Foundation (NSF) under Grant no. DEB-1353131. This research used computational resources available through the Arkansas High Performance Computing Center, which was funded through multiple NSF grants and the Arkansas Economic Development Commission.

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The authors declare that they have no conflict of interest.

Correspondence to Teofil Nakov.

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