Assessment of biodiversity, global distribution, and putative ecological niches of suessiacean dinoflagellates by DNA metabarcoding

Abstract

Dinoflagellates in the family Suessiaceae, so-called suessiacean dinoflagellates, play diverse roles in aquatic ecosystems, being distributed from tropical to polar waters and from marine to freshwater habitats and encompassing free-living forms, symbionts, and parasites. Despite their importance due to the variety of ecological roles and biodiversity, very few studies have characterized small suessiacean species. Recent advances in molecular techniques could provide insights into the yet unexplored ecological roles they play in aquatic environments. Using a global DNA metabarcoding dataset, this study elucidated the hidden biodiversity, global distribution, and ecological characteristics of suessiacean dinoflagellates. The results of this study indicated that the family Suessiaceae was the sixth highest in terms of read count and the ninth highest in terms of amplicon sequence variant (ASV) richness from a total of 42 categorized dinoflagellate families, suggesting that their global abundance has been greatly underestimated. Furthermore, metabarcodes of suessiacean dinoflagellates were found to be cosmopolitan in distribution, although the ecological niche of each taxon was distinctly different within the group based on their latitudinal and vertical distribution patterns. Moreover, phylogenetic analysis discovered at least five new phylogenetic groups and three new individual species within the family. Collectively, the findings of this study highlight the significance of suessiacean dinoflagellates in global aquatic ecosystems and reveal the importance of big data obtained from environmental DNA in exploring the ecological functions of understudied species.

The second most abundant dinophyte in the ponds of a botanical garden is a species new to science

“…The situation of biodiversity assessment still seems particularly precarious in the microscopy realm, where species are often only recognizable to a limited extent due to the lack of diagnostic traits. Especially, the metabarcoding studies of recent years with their extensive share of dark diversity (Jang, 2022;Mahé et al, 2017) have contributed to this insight. Some of these studies have been the basis for research into hitherto completely unknown evolutionary lineages such as Picomonas Seenivasan, Sausen, Medlin & Melkonian (Seenivasan et al, 2013) or Ancoracysta Janoušk., Tikhonenkov, Burki, A.T.Howe, F.L.Rohwer, A.P.Mylnikov & P.J.Keeling (Janouškovec et al, 2017) with isolated positions in the Tree of Life.…”

“…Numerous studies have generated previously unknown DNA sequences, some of which could not even be assigned to one of the established major phylogenetic lineages (Janouškovec et al., 2017; Massana, 2011; Seenivasan et al., 2013). Even within known lineages, there is a considerable amount of diversity that currently cannot be associated with a scientific name (Jang, 2022), ultimately due to the incompleteness of reference databases (“taxonomic gap”) that are currently available (Gottschling et al., 2020; Salmaso et al., 2022). Without the basis of a reliable identification and naming of species, however, further research, for example, on the role of species in the ecosystem, is hardly possible (Hebert et al., 2003; Thomson et al., 2018; Vitorino & Bessa, 2018).…”

“…As inferred from metabarcoding, suessialean dinophytes include a reasonable fraction of so far unknown or “dark” diversity (Jang, 2022), also among the freshwater lineages (Annenkova et al., 2011; Gottschling et al., 2021). One of the early branches of the †Suessiales is the Borghelliaceae (Knechtel et al., 2020; Moestrup et al., 2009) currently encountering 11 known species from freshwater habitats.…”

Protistan community structure and the influence of a branch of Kuroshio in the northeastern East China Sea during the late spring

“…However, with the development of various observational technologies, specific analyses of community structure have been actively conducted in recent years (Olson and Sosik, 2007;Lombard et al, 2019;Jang et al, 2022). One way to investigate taxonomic composition, relative species abundance, and spatiotemporal distribution in planktonic communities is DNA metabarcoding, which can be achieved by sequencing a short DNA region at a reasonable cost (Cuvelier et al, 2010;De Vargas et al, 2015;Abad et al, 2016;Jang, 2022). Moreover, the high sensitivity of this technique allows for the detection of rare taxa and identification of cryptic species that are typically overlooked by conventional microscopy observations because they are either too small or fragile (De Vargas et al, 2015;Abad et al, 2016).…”