TitleSexual ancestors generated an obligate asexual and globally dispersed clone within the model diatom species Thalassiosira pseudonana.
Publication TypeJournal Article
Year of Publication2018
AuthorsKoester JA, Berthiaume CT, Hiranuma N, Parker MS, Iverson V, Morales R, Ruzzo WL, E Armbrust V
JournalSci Rep
Date or Month Published2018 Jul 12

Sexual reproduction roots the eukaryotic tree of life, although its loss occurs across diverse taxa. Asexual reproduction and clonal lineages persist in these taxa despite theoretical arguments suggesting that individual clones should be evolutionarily short-lived due to limited phenotypic diversity. Here, we present quantitative evidence that an obligate asexual lineage emerged from a sexual population of the marine diatom Thalassiosira pseudonana and rapidly expanded throughout the world's oceans. Whole genome comparisons identified two lineages with characteristics expected of sexually reproducing strains in Hardy-Weinberg equilibrium. A third lineage displays genomic signatures for the functional loss of sexual reproduction followed by a recent global colonization by a single ancestral genotype. Extant members of this lineage are genetically differentiated and phenotypically plastic, potentially allowing for rapid adaptation when they are challenged by natural selection. Such mechanisms may be expected to generate new clones within marginal populations of additional unicellular species, facilitating the exploration and colonization of novel environments, aided by exponential growth and ease of dispersal.

Alternate JournalSci Rep
Citation Key14900
PubMed ID30002405
PubMed Central IDPMC6043606
Grant ListGBMF3776 / / Gordon and Betty Moore Foundation /