Seminar Details

The global diversity of planktonic foraminifera




Dr. Raphaël Morard - MARUM Center for Marine Environmental Sciences, University of Bremen, Germany


Planktonic foraminifera is a group of ubiquitous pelagic marine protists with reticulated pseudopods secreting a calcareous shell and clustering within the Rhizaria. Since their first systematic description by d’Orbigny (1826), planktonic foraminifera have been a cornerstone of marine sediments dating and paleoceanographic reconstructions. Their global geographic distribution, seasonal dynamics and trophic behavior have been studied by sampling in the plankton, sediment traps and surface sediments but the vast majority of existing data are based on morphological species concept. The vision on the diversity of planktonic foraminifera has been challenged by the first single-cell genetic analyses of the ribosomal Small Sub Units (SSU rDNA) of planktonic foraminifera in the mid 90’s. Sequencing of individual specimens attributed to the same morphological taxa collected across oceanic provinces showed large divergences among their DNA sequences compatible with the presence of several biological species, which appear to be morphologically “cryptic”. The subsequent three decades of single-cell barcoding carried out by multiple research teams lead to the publication of ~30 scientific papers describing the extent of the cryptic diversity in extant species of planktonic foraminifera. Yet, this large body of knowledge lacked a common molecular taxonomic framework for a robust assessment of the global diversity in planktonic foraminifera. To this end, a comprehensive dataset of ~7000 single sequences belonging to 40 of the 47 known morphospecies collected from ~700 collection sites was assembled and using automated delimitation methods bestowed with strict nomenclatural rules, DNA sequence diversity was structured into a 3-level hierarchal taxonomy below the morphospecies level. Finally, to assess the global diversity of planktonic foraminifera we investigated the occurrence of planktonic foraminifera environmental into the Tara Ocean expedition metabarcoding dataset, which has a worldwide coverage of the photic plankton zone. The resulting synthesis allows us to estimate the global extent of genetic diversity in the group and constrain the major biogeographic and ecologic features of planktonic foraminifera diversity.

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