Abstract
Like meiofauna in general, tardigrades are often neglected in ecological and environmental surveys. Tardigrades occur in all parts of the world, from deep marine sediments to alpine environments, and are present in most ecosystems. They are therefore potentially good candidates for biomonitoring programs. However, sampling of these minute animals is both tedious and time-consuming, impeding their inclusion in large-scale ecological surveys. In this study we argue that using a multi-marker metabarcoding approach on environmental DNA (eDNA) partly can overcome this barrier. Samples of moss, lichens, and leaf litter were investigated both by morphology-based methods and DNA metabarcoding, and the results were compared in terms of tardigrade diversity and community composition of the sampled microhabitats. DNA metabarcoding using three markers detected more species of tardigrades than identification by morphology in most samples. Also, metabarcoding detected the same community differences and microhabitat distribution patterns as morphology-based methods. In general, metabarcoding of litter samples was unreliable, with only one out of three markers consistently amplifying and detecting tardigrades. The low availability of tardigrade reference sequences in public databases restricts the taxonomic resolution in eDNA surveys, but this impediment is partly circumvented by utilizing multiple markers.
Highlights
Tardigrades are hygrophilous, microscopic invertebrates inhabiting most ecosystems on earth
This study aimed to investigate whether metabarcoding of environmental DNA successfully captures tardigrade diversity
Of the 24 obtained morpho-species sequenced for c oxidase subunit I gene (COI) barcode construction (32 barcodes revealed six distinct genetic clusters (BINs)), all DNA-species and BINs except Pseudechiniscus suillus and one cryptic variant of the Mesobiotus harmsworthi group were retrieved by both COI markers
Summary
Tardigrades are hygrophilous, microscopic invertebrates inhabiting most ecosystems on earth. Whereas the distribution of many tardigrade species has received notable attention, studies investigating habitat specificity and preference of species have been found to lack sufficient sampling effort (e.g., Guidetti et al 1999; Ito 1999; Nelson and Bartels 2007), even in cases with sample size exceeding 1000 samples (Nelson et al 2019) Such studies, which are mostly based on morphology, are timeconsuming, require a high taxonomic expertise, and often require the presence of both adult animals and eggs for confident identifications (Guidetti and Bertolani 2005). These efforts commonly still fail to identify a notable portion of the specimens to species level
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