Searching for hidden diversity among the phylum Platyhelminthes using global metabarcoding data

• Published in: Genome Vol. 60; no. 11; p. 974
• Main Authors: Mitsi, Konstantina, Sanchez-Arroyo, Alicia, Ruiz-Trillo, Inaki
• Format: Journal Article
• Language: English
• Published: Ottawa Canadian Science Publishing NRC Research Press 01.11.2017
• Subjects: Bar codes; Biodiversity; Dark matter; Data analysis; Data processing; Deoxyribonucleic acid; DNA; Ecological effects; Ecological monitoring; Freshwater lakes; Genetics; Invertebrates; Marine technology; Phylogeny; Platyhelminthes; Rivers; Sequences
• ISSN: 0831-2796; 1480-3321

Background: During the last decade, several initiatives have been taken to explore the marine diversity using high-throughput technologies. As a result, a bulk of metabarcoding data are now available. Using these data, we aimed to better understand the real diversity of the acoelomate Platyhelminthes, an evolutionary and ecologically important clade of animals with both free-living and parasitic species. Results: In this study, we analyzed data from seven marine (Malaspina, METABARPARKS, TaraOcean, TaraArctic, BioMarks, Blanes, DeepSea) and two freshwater (Parana River, Lake Sanabria) metabarcoding projects under a phylogenetic framework. Our main objective is to get a better insight into the diversity of Platyhelminthes and to recognize novel clades of the free-living representatives of this phylum. To achieve our goal, we first built a reference tree using 18S rDNA Gen- Bank sequences covering all known phylogenetic diversity of Platyhelminthes. We performed a phylogenetic placement of the clustered operational taxonomic units (OTUs) from the different environmental datasets in order to retain sequences with interesting phylogenetic position within, or close to, Platyhelminthes. We then used these sequences to reconstruct the phylogeny of the phylum. Furthermore, we combined our phylogenetic results with data of abundance and other ecological parameters to assess the worldwide distribution of the different clades within Platyhelminthes. Significance: To our knowledge, this is the first effort to compile such a rich and diverse dataset in order to address the question of hidden diversity within the phylum Platyhelminthes. Apart from the well-studied planarians, polyclads, and neodermatans, very little is known about the rest of the flatworm orders that are usually collectively referred to as "microturbellarians". We expect not only to better understand the diversity patterns of all Platyhelminthes but to also unravel previously undescribed free-living clades, to gain a better understanding of the microturbelarian "dark matter" and to make inferences of their ecology.