Cited by 326Protist diversity and phylogenyMarine Invertebrate Physiology and EcologyGenomics and Phylogenetic Studies

The Closest Unicellular Relatives of Animals

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Lang, B.F., O'Kelly, C., Nerad, T., Gray, M.W., Burger, G.·2002·Current Biology

Abstract

Molecular phylogenies support a common ancestry between animals (Metazoa) and Fungi, but the evolutionary descent of the Metazoa from single-celled eukaryotes (protists) and the nature and taxonomic affiliation of these ancestral protists remain elusive. We addressed this question by sequencing complete mitochondrial genomes from taxonomically diverse protists to generate a large body of molecular data for phylogenetic analyses. Trees inferred from multiple concatenated mitochondrial protein sequences demonstrate that animals are specifically affiliated with two morphologically dissimilar unicellular protist taxa: Monosiga brevicollis (Choanoflagellata), a flagellate, and Amoebidium parasiticum (Ichthyosporea), a fungus-like organism. Statistical evaluation of competing evolutionary hypotheses confirms beyond a doubt that Choanoflagellata and multicellular animals share a close sister group relationship, originally proposed more than a century ago on morphological grounds. For the first time, our trees convincingly resolve the currently controversial phylogenetic position of the Ichthyosporea, which the trees place basal to Choanoflagellata and Metazoa but after the divergence of Fungi. Considering these results, we propose the new taxonomic group Holozoa, comprising Ichthyosporea, Choanoflagellata, and Metazoa. Our findings provide insight into the nature of the animal ancestor and have broad implications for our understanding of the evolutionary transition from unicellular protists to multicellular animals.

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  1. [8]8. Pearson, W.R. (1990). Rapid and sensitive sequence compari- son with FASTP and FASTA. Methods Enzymol. 183, 63-98.

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Authors
Lang, B. F., O'Kelly, C., Nerad, T., Gray, M. W., & Burger, G.
Affiliations
  • Canadian Institute for Advanced Research (CA)
  • American Type Culture Collection (US)
Corresponding author
Burger, G.
Venue
Current Biology
Publisher
Elsevier BV
Published
2002-10
Volume
12
Issue
20
Pages
1773-1778
ISSN
0960-9822 (ISSN-L)
OpenAlex
W1999681000
Cited by
326
References
34
Citations by year
2026: 4 · 2025: 4 · 2024: 6 · 2023: 14 · 2022: 5 · 2021: 9 · 2020: 14 · 2019: 8 · 2018: 5 · 2017: 11 · 2016: 12 · 2015: 7 · 2014: 16 · 2013: 12 · 2012: 16
FWCI
7.18
Type
journal article
Language
en
Open access
Locations
  • Current Biology (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Protist diversity and phylogeny
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Marine Invertebrate Physiology and Ecology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Genomics and Phylogenetic Studies
Keywords
animal origins, Choanoflagellata, Ichthyosporea, Monosiga brevicollis, mitochondrial genome, evolution of multicellularity, protist phylogeny
MeSH terms
Animals, DNA, Mitochondrial, Biological Evolution, Fungi, Molecular Sequence Data, Phylogeny, Plants, Eukaryota

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