Agnes Weiner

Norce Research · Climate and Environment

Microbial eukaryotes (aka protists) are known for their important roles in nutrient cycling across different ecosystems. However, the composition and function of protist-associated microbiomes remains largely elusive. Here, we employ cultivation-independent single-cell isolation and genome-resolved metagenomics to provide detailed insights into und...

Environmental DNA (eDNA) preserved in marine sediments is increasingly being used to study past ecosystems. However, little is known about how accurately marine biodiversity is recorded in sediment eDNA archives, especially planktonic taxa. Here, we address this question by comparing eukaryotic diversity in 273 eDNA samples from three water depths...

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 des...

The enormous population sizes and wide biogeographical distribution of many microbial eukaryotes set the expectation of high levels of intraspecific genetic variation. However, studies investigating protist populations remain scarce, mostly due to limited 'omics data. Instead, most genetics studies of microeukaryotes have thus far relied on single...

While general trends in the inflow of Atlantic Water (AW) to the European Arctic over the present interglacial (the Holocene) are well known, regional changes in climate and the AW current and subsequent environmental responses are less well established. In particular, there is only limited knowledge on the development of ocean currents after the l...

Sedimentary ancient DNA (sedaDNA) offers a novel retrospective approach to reconstructing the history of marine ecosystems over geological timescales. Until now, the biological proxies used to reconstruct paleoceanographic and paleoecological conditions were limited to organisms whose remains are preserved in the fossil record. The development of a...

Knowledge of eukaryotic life cycles and associated genome dynamics stems largely from research on animals, plants, and a small number of “model” (i.e., easily cultivable) lineages. This skewed sampling results in an underappreciation of the variability among the many microeukaryotic lineages, which represent the bulk of eukaryotic biodiversity. The...

Foraminifera, classified in the supergroup Rhizaria, are a common and highly diverse group of mainly marine protists. Despite their evolutionary and ecological importance, only limited genomic data (one partial genome and nine transcriptomic datasets) have been published for this group. Foraminiferal molecular phylogeny is largely based on 18S rRNA...

Understanding the biology of reproduction of an organismal lineage is important for retracing key evolutionary processes, yet gaining detailed insights often poses major challenges. Planktonic Foraminifera are globally distributed marine microbial eukaryotes and important contributors to the global carbon cycle. They cannot routinely be cultured un...

Understanding the biology of reproduction of an organismal lineage is important for retracing key evolutionary processes, yet gaining detailed insights often poses major challenges. Planktonic Foraminifera are globally distributed marine microbial eukaryotes and important contributors to the global carbon cycle. They cannot routinely be cultured un...

This is R-code which allows to estimate the number of gametes produced by planktonic Foraminifera, based on shell cross-sectional area and shell weight. A variety of morphological types is available for the calculations and the main parameters for the estimation can be adjusted.

Symbiotic relationships between heterotrophic and phototrophic partners are common in microbial eukaryotes. Among Arcellinida (Amoebozoa) several species are associated with microalgae of the genus Chlorella (Archaeplastida). So far, these symbioses were assumed to be stable and mutualistic, yet details of the interactions are limited. Here, we ana...

Though acting as a major component of eukaryotic biodiversity, many microbial eukaryotes remain poorly studied, including the focus of the present work, testate amoebae of the order Arcellinida (Amoebozoa) and non-model lineages of ciliates (Alveolata). In particular, knowledge of their genome structures and changes in genome content over their oft...

Understanding the biology of reproduction is important for retracing key evolutionary processes (e.g. speciation and adaptation) in any group of organisms, yet gaining detailed insights often poses a major challenge. Planktonic Foraminifera are a group of globally distributed marine microbial eukaryotes that are important contributors to the global...

Since the seminal paper in 1998 (Coolen and Overmann), sedimentary ancient DNA (sedaDNA) has become a powerful tool in paleoecology to reconstruct past changes in terrestrial and aquatic biodiversity. Still, sedaDNA is an emerging tool and there is a need for calibrations and validations to ensure the reliability of sedaDNA as a proxy to reconstruc...

Understanding the biology of reproduction is important for retracing key evolutionary processes (e.g. speciation and adaptation) in any group of organisms, yet gaining detailed insights often poses a major challenge. Planktonic Foraminifera are a group of globally distributed marine microbial eukaryotes that are important contributors to the global...

Microbial eukaryotes, i.e., protists, represent the bulk of eukaryotic diversity in terms of species diversity and biomass. Protists are globally distributed in all ecosystems and play important roles in food webs and nutrient cycles. To date it remains enigmatic how protist diversity is generated, especially in lineages with large populations in e...

Understanding the biology of reproduction is important for retracing evolutionary processes in organisms, yet gaining detailed insights poses a major challenge. Planktonic Foraminifera are globally distributed marine protists that are important contributors to the carbon cycle and are widely used as environmental proxies. Hypotheses on their divers...

Reproductive biology is integral to evolutionary processes in organisms, yet gaining detailed insights poses major challenges. Planktonic Foraminifera are globally distributed marine protists and important contributors to the global carbon cycle with distinct biodiversity patterns. Knowledge on their life cycle remains incomplete, yet the productio...

Understanding the biology of reproduction is important for retracing key evolutionary processes (e.g. speciation and adaptation) in any group of organisms, yet gaining detailed insights often poses a major challenge. Planktonic Foraminifera are a group of globally distributed marine microbial eukaryotes that are important contributors to the global...

Understanding the biology of reproduction is important for retracing key evolutionary processes in organisms, yet gaining detailed insights often poses major challenges. Planktonic Foraminifera are globally distributed marine microbial eukaryotes and important contributors to the global carbon cycle. Their extant biodiversity shows restricted distr...

Epigenetic processes in eukaryotes play important roles through regulation of gene expression, chromatin structure and genome rearrangements. Mechanisms such as chromatin modification (e.g. DNA methylation, histone modification) and non-protein-coding RNAs (npc-RNAs) have been well studied in animals and plants. With the exception of a few model or...

Testate (shell‐building) amoebae, such as the Arcellinida (Amoebozoa), are useful bioindicators for climate change. Though past work has relied on morphological analyses to characterize Arcellinida diversity, genetic analyses revealed the presence of multiple cryptic species underlying morphospecies. Here, we design and deploy Arcellinida‐specific...

The state of a population of planktic foraminifers at a certain time reflects multiple processes in the upper ocean, including environmental conditions to which the population was exposed during its growth, the age of the cohorts, and spatiotemporal patchiness. We carried out depth-stratified (0-60, 60-100 m) replicated sampling off Puerto Rico in...

The state of a population of planktic foraminifers at a certain time reflects multiple processes in the upper ocean, including environmental conditions to which the population was exposed during its growth, the age of the cohorts, and spatiotemporal patchiness. We carried out depth-stratified (0–60, 60–100 m) replicated sampling off Puerto Rico in...

The planktonic foraminifera genus Globigerinoides provides a prime example of a species-rich genus in which genetic and morphological divergence are uncorrelated. To shed light on the evolutionary processes that lead to the present-day diversity of Globigerinoides, we investigated the genetic, ecological and morphological divergence of its constitu...

Testate amoebae (Amoebozoa, Arcellinida) are a group of unicellular eukaryotes that build shells around their cell. These shells are well preserved in the fossil record. Arcellinida communities are sensitive to environmental changes, such as shifts in temperature, moisture and pH. Therefore, they have been used extensively as bioindicators to recon...

Shell-building amoebae (Amoebozoa) are microbial eukaryotes that are highly abundant in freshwater ecosystems and represent top predators (i.e. feed on other microbes, small animals). Because of their abundance, sensitivity to abiotic environmental factors and the preservation of their tests in the fossil record, testate amoebae serve as excellent...

Xenophyophores are a diverse group of large agglutinated monothalamous Foraminifera. Their often delicate tests can measure several centimeters in size and contain the system of organic tubes containing cytoplasm (the granellare) and membrane-bound strands of waste pellets (the stercomare). All known species were found in the deep sea. According to...

Understanding the biology of reproduction is of fundamental importance to retrace key evolutionary processes, such as speciation and adaptation in any group of organisms. For planktonic Foraminifera, due to their fossil record, a wealth of knowledge exists on species turnover throughout their evolutionary history and their distribution patterns are...

Foraminifera are one of the most abundant taxa in the deep sea; our sampling in the Sea of Okhotsk and the adjacent Pacific during the SokhoBio cruise surfaced a large number of different species unique to this ecosystem. Many deep-sea Foraminifera are characterized by the formation of agglutinated tests, made up of material from the surrounding en...

The transition from benthos to plankton requires multiple adaptations, yet so far it remains unclear how these are acquired in the course of the transition. To investigate this process, we analyzed the genetic diversity and distribution patterns of a group of foraminifera of the genus Bolivina with a tychopelagic mode of life (same species occurrin...

Single-cell genetic analysis is an essential method to investigate the biodiversity and evolutionary ecology of marine protists. In protist groups that do not reproduce under laboratory conditions, this approach provides the only means to directly associate molecular sequences with cell morphology. The resulting unambiguous taxonomic identification...

Investigations of biodiversity, biogeography and ecological processes rely on the identification of "species" as biologically significant, natural units of evolution. In this context, morpho-taxonomy only provides an adequate level of resolution if reproductive isolation matches morphological divergence. In many groups of organisms, morphologically...

Molecular genetic investigations of the highly abundant extant planktonic foraminifera plexus Globigerinella siphonifera/Globigerinella calida have recently shown this group to be the genetically most diverse one within planktonic foraminifera, separating it into 12 distinct genetic types belonging to three main genetic lineages. Independently, sev...

Planktonic foraminifera are widely used as proxies for the reconstruction of past ocean conditions, a method that requires exact species classification and knowledge of their ecological adaptations. Species classification traditionally was conducted using morphological characteristics of the calcite shell. The application of genetic approaches on l...

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 rDN...

Previous genetic studies of extant planktonic foraminifera have provided evidence that the traditional, strictly morphological definition of species in these organisms underestimates their biodiversity. Here, we report the first case where this pattern is reversed. The modern (sub)tropical species plexus Globigerinoides sacculifer is characterized...

A large portion of the surface-ocean biomass is represented by microscopic unicellular plankton. These organisms are functionally and morphologically diverse, but it remains unclear how their diversity is generated. Species of marine microplankton are widely distributed because of passive transport and lack of barriers in the ocean. How does specia...

The model organism Pyrococcus furiosus has recently been reported to interact with Methanopyrus kandleri in coculture, suggesting a H2 symbiosis. In the current study we further investigated this hypothesis by growing P. furiosus with four other hyperthermophilic methanogens providing evidence that the organisms did not only exert positive effects...