Sandin MM - Research

My interests in ecology began during my bachelor studies in Biology, where I was actively involved in the ecology department at Oviedo University trying to understand macroalgal diversity and its relationships with the environment and other organisms. Next, I pursued an international Master in Science in Marine Biodiversity and Conservation, where I obtained insights on eukaryotic diversity in today’s oceans and different approaches for its exploration. After gaining this ecological background, I was deeply interested in understanding not only biotic and abiotic relationships, but also exploring how past interactions may have shaped current diversity. Therefore, I carried out a PhD thesis on the molecular evolution and diversity of a widely distributed protist group, the Radiolaria, with Fabrice Not as supervisor at the Biological Station of Roscoff.

During my PhD project I built a reference morpho-molecular framework of Radiolaria, an ubiquitous and abundant planktonic group whose biology is little known. I gained extensive experience on single-cell isolation and characterization of protistan lineages. My PhD began with the characterization of specific orders of Radiolaria, in which I built a taxonomic framework combining morphological synapomorphies and molecular phylogenies to define morpho-molecular clades. Their excellent fossil record allowed me to calibrate a Bayesian molecular clock and to reconstruct their evolutionary history linked to global environmental and geological changes (Sandin et al., 2019; Sandin et al., 2021). These results were presented in the InterRad congress in Japan, where I was awarded the prize for the best talk for young scientists. The establishment of the reference morpho-molecular framework of Radiolaria allowed me to explore their extant diversity and biogeography in the world oceans by a metabarcoding approach, thanks to global molecular-based datasets such as the Tara oceans or Malaspina expeditions. Altogether, I integrated the most extensive, non-redundant rDNA dataset of Radiolaria to date through a detailed curation of all available molecular barcodes and environmental markers (Sandin et al., in prep). I have further strengthened a solid expertise on single-cell molecular approaches with the use of novel high-throughput sequencing techniques (such as the MinION sequencing device from Oxford Nanopore Technologies) for the exploration of intragenomic genetic diversity (Sandin et al., 2022).

After this wonderful experience I was fascinated by deep and ancient eco-evolutionary processes, and I wanted to challenge the scarce and sporadic fossil record of the early life of eukaryotes. Together with Dr. Fabien Burki developed a postdoctoral project to unveil the evolutionary processes that led eukaryotes to evolve into this incredible diversity that we observe today. In this project, I fit macro-evolutionary models into an ecological perspective to explore the diversification of eukaryotes through geological times at a broad phylogenetic scale. Uniquely, I integrated both long-read and short-read environmental rDNA sequences along with phylogenetically curated reference sequences to access the majority of the known eukaryotic molecular diversity. I then fossil calibrated the eukaryotic tree of life to infer diversification patterns throughout the history of eukaryotes. Here, I am showing that early eukaryotic diversification was initially slow and that biotic interactions established the main groups that we observe today, setting the basis for their later expansion (Sandin et al., in prep). Through my research, I have acquired extensive knowledge in eukaryotic diversity as well as in large-scale phylogenetic analysis, leading to the publication of a review on the state of the art of microbial eukaryotes (protists) diversity (Burki, Sandin and Jamy, 2021).

In my next postdoctoral project, I will merge efforts with Daniel Richter and Ramon Massana to explore the vast undescribed diversity of microbial eukaryotes that we only know from their short environmental DNA sequences. I will unveil the morphology and genomes of uncharted protist to study their role in the macro-evolution of eukaryotes. This project will attempt to reconstruct an unbiased evolutionary history of eukaryotes.