The global genetic diversity of planktonic foraminifera reveals the structure of cryptic speciation in plankton.

The nature and extent of diversity in the plankton has fascinated scientists for over a century. Initially, the discovery of many new species in the remarkably uniform and unstructured pelagic environment appeared to challenge the concept of ecological niches. Later, it became obvious that only a fraction of plankton diversity had been formally described, because plankton assemblages are dominated by understudied eukaryotic lineages with small size that lack clearly distinguishable morphological features.

16S rRNA gene metabarcoding and TEM reveals different ecological strategies within the genus Neogloboquadrina (planktonic foraminifer).

Uncovering the complexities of trophic and metabolic interactions among microorganisms is essential for the understanding of marine biogeochemical cycling and modelling climate-driven ecosystem shifts. High-throughput DNA sequencing methods provide valuable tools for examining these complex interactions, although this remains challenging, as many microorganisms are difficult to isolate, identify and culture. We use two species of planktonic foraminifera from the climatically susceptible, palaeoceanographically important genus Neogloboquadrina, as ideal test microorganisms for the application of 16S rRNA gene metabarcoding.

Nomenclature for the Nameless: A Proposal for an Integrative Molecular Taxonomy of Cryptic Diversity Exemplified by Planktonic Foraminifera.

Investigations of biodiversity, biogeography, and ecological processes rely on the identification of "species" as biologically significant, natural units of evolution. In this context, morphotaxonomy only provides an adequate level of resolution if reproductive isolation matches morphological divergence. In many groups of organisms, morphologically defined species often disguise considerable genetic diversity, which may be indicative of the existence of cryptic species.

PFR²: a curated database of planktonic foraminifera 18S ribosomal DNA as a resource for studies of plankton ecology, biogeography and evolution.

Planktonic foraminifera (Rhizaria) are ubiquitous marine pelagic protists producing calcareous shells with conspicuous morphology. They play an important role in the marine carbon cycle, and their exceptional fossil record serves as the basis for biochronostratigraphy and past climate reconstructions. A major worldwide sampling effort over the last two decades has resulted in the establishment of multiple large collections of cryopreserved individual planktonic foraminifera samples.

Phylogeography of the tropical planktonic foraminifera lineage globigerinella reveals isolation inconsistent with passive dispersal by ocean currents.

Morphologically defined species of marine plankton often harbor a considerable level of cryptic diversity. Since many morphospecies show cosmopolitan distribution, an understanding of biogeographic and evolutionary processes at the level of genetic diversity requires global sampling. We use a database of 387 single-specimen sequences of the SSU rDNA of the planktonic foraminifera Globigerinella as a model to assess the biogeographic and phylogenetic distributions of cryptic diversity in marine microplankton on a global scale.

Ecological partitioning and diversity in tropical planktonic foraminifera.

Background: Ecological processes are increasingly being viewed as an important mode of diversification in the marine environment, where the high dispersal potential of pelagic organisms, and a lack of absolute barriers to gene flow may limit the occurrence of allopatric speciation through vicariance. Here we focus on the potential role of ecological partitioning in the diversification of a widely distributed group of marine protists, the planktonic foraminifera. Sampling was conducted in the tropical Arabian Sea, during the southwest (summer) monsoon, when pronounced environmental conditions result in a strong disparity in temperature, salinity and productivity between distinct northern and southern water masses.

Surviving mass extinction by bridging the benthic/planktic divide.

Evolution of planktic organisms from benthic ancestors is commonly thought to represent unidirectional expansion into new ecological domains, possibly only once per clade. For foraminifera, this evolutionary expansion occurred in the Early-Middle Jurassic, and all living and extinct planktic foraminifera have been placed within 1 clade, the Suborder Globigerinina. The subsequent radiation of planktic foraminifera in the Jurassic and Cretaceous resulted in highly diverse assemblages, which suffered mass extinction at the end of the Cretaceous, leaving an impoverished assemblage dominated by microperforate triserial and biserial forms.

Global molecular phylogeography reveals persistent Arctic circumpolar isolation in a marine planktonic protist.

The high-latitude planktonic foraminifera have proved to be particularly useful model organisms for the study of global patterns of vicariance and gene flow in the oceans. Such studies demonstrate that gene flow can occur over enormous distances in the pelagic marine environment leading to cosmopolitanism but also that there are ecological and geographical barriers to gene flow producing biogeographic structure. Here, we have undertaken a comprehensive global study of genetic diversity within a marine protist species, the high-latitude planktonic foraminiferan Neogloboquadrina pachyderma.

Molecular evidence links cryptic diversification in polar planktonic protists to Quaternary climate dynamics.

It is unknown how pelagic marine protists undergo diversification and speciation. Superficially, the open ocean appears homogeneous, with few clear barriers to gene flow, allowing extensive, even global, dispersal. Yet, despite the apparent lack of opportunity for genetic isolation, diversity is prevalent within marine taxa.

Cryptic species of planktonic foraminifera: their effect on palaeoceanographic reconstructions.

Shells of planktonic foraminifera recovered from marine sediments provide a multitude of important palaeoproxies. Most of these proxies are based on the assumption that each morphospecies of planktonic foraminifera represents a genetically continuous species with a unique habitat. Recent discovery of hitherto hidden genetic diversity among modern planktonic foraminifera has significant repercussions on palaeoproxies derived from their fossil shells.