Contemporary issues, current best practice and ways forward in soil
protist ecology
Abstract
Soil protists are increasingly studied due to a release from previous
methodological constraints and the acknowledgement of their immense
diversity and functional importance in ecosystems. However, these
studies often lack a sufficient depth in knowledge, which is visible in
the form of falsely used terms and false- or over-interpreted data with
conclusions that cannot be drawn from the data obtained. As we welcome
that also non-experts include protists in their still mostly bacterial
and/or fungal focused studies, our aim here is to help avoid some common
errors. We provide an overview of current terms to be used when working
on soil protists, like protist instead of protozoa, predator instead of
grazer, microorganisms rather than microflora and terms to be used to
describe the prey spectrum of protists. We then highlight some do’s and
don’ts in soil protist ecology including challenges related to
interpreting 18S rRNA gene amplicon sequencing data. We caution against
the use of standard bioinformatic settings optimized for bacteria and
the uncritical reliance on incomplete and partly erroneous reference
databases. We also show why causal inferences cannot be drawn from
sequence-based correlation analyses or any sampling/monitoring, study in
the field without thorough experimental confirmation and sound
understanding of the biology of taxa. Together, we envision this work to
help non-experts to more easily include protists in their soil ecology
analyses, and obtain more reliable interpretations from their protist
data and other biodiversity data that, in the end, will help to better
understand soil ecology.