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The widely used small subunit 18S rDNA molecule greatly underestimates true diversity in biodiversity surveys of the meiofauna

Cuong Q. TANG

Molecular tools have revolutionized the exploration of biodiversity, especially in organisms for which traditional taxonomy is difficult, such as for microscopic animals (meiofauna). Environmental (eDNA) metabarcode surveys of DNA extracted from sediment samples are increasingly popular for surveying biodiversity. Most eDNA surveys use the nuclear gene-encoding small subunit rDNA gene (18S) as a marker; however, different markers and metrics used for delimiting species have not yet been evaluated against each other or against morphologically defined species (morphospecies). We assessed more than 12,000 meiofaunal sequences of 18S and of the main alternatively used marker [Cytochrome c oxidase subunit I (COI) mtDNA] belonging to 55 datasets covering three taxonomic ranks. Our results show that 18S reduced diversity estimates by a factor of 0.4 relative to morphospecies, whereas COI increased diversity estimates by a factor of 7.6. Moreover, estimates of species richness using COI were robust among three of four commonly used delimitation metrics, whereas estimates using 18S varied widely with the different metrics. We show that meiofaunal diversity has been greatly underestimated by 18S eDNA surveys and that the use of COI provides a better estimate of diversity. The suitability of COI is supported by cross-mating experiments in the literature and evolutionary analyses of discreteness in patterns of genetic variation. Furthermore its splitting of morphospecies is expected from documented levels of cryptic taxa in exemplar meiofauna. We recommend against using 18S as a marker for biodiversity surveys and suggest that use of COI for eDNA surveys could provide more accurate estimates of species richness in the future.

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Editorial board
  • BRANDNER Melissa
    • University of Nordland
    • Bodø (Norway)
  • BROCHMANN Christian
    • National Centre for Biosystematics
    • Oslo (Norway)
  • CHARITON Anthony
    • CSIRO Land and Water
    • Lucas Heights NA (Australia)
  • DEAGLE Bruce
    • University of Victoria
    • Victoria (Canada)
  • Eric Coissac
    • LECA
    • Grenoble (France)
  • KASAPIDIS Panagiotis
    • Hellenic Center for Marine Research
    • Irakleion, Crete (Greece)
    • Université de Genève
    • Genève 4 (Switzerland)
  • TABERLET Pierre
    • LECA,
    • Grenoble (France)
    • Centre for GeoGenetics
    • Copenhagen (Denmark)
  • ZINGER Lucie
    • IBENS
    • Paris (France)
  • Vodka, Bison and Metabarcoding

    31 July 2015, by BRANDNER Melissa

    The start of last month saw the occurrence of the Fifth Metabarcoding Spring School held in Białowieża National Park , Poland. A variety of scientists attended from all over the globe to learn, share and inspire with unique stories of metabarcoding.
    The scientists at the Mammal Research Institute PAS in Białowieża National Park hosted this year’s workshop. And our hats go off to them for the organizational skills, warmth and hospitality. During the week, experienced metabarcoders gave lectures on their trials and tribulations in the field of metabarcoding, sparking conversations between the attendees. The end of the first day saw flash talks from all participants of the event, creating an icebreaker and showing the wide variety of applications for metabarcoding, including, dietary studies, environmental health, fundamental ecology and exploration of rare and ancient habitats.
    Pierre Taberlet (who is rumoured to run 8000 PCR a day!) taught technical aspects such as DNA extraction in (...)

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