Journal of Molecular Evolution

, Volume 42, Issue 2, pp 183–193

Evolutionary relationships of eukaryotic kingdoms

  • Sudhir Kumar
  • Andrey Rzhetsky

DOI: 10.1007/BF02198844

Cite this article as:
Kumar, S. & Rzhetsky, A. J Mol Evol (1996) 42: 183. doi:10.1007/BF02198844


The evolutionary relationships of four eukaryotic kingdoms—Animalia, Plantae, Fungi, and Protista—remain unclear. In particular, statistical support for the closeness of animals to fungi rather than to plants is lacking, and a preferred branching order of these and other eukaryotic lineages is still controversial even though molecular sequences from diverse eukaryotic taxa have been analyzed. We report a statistical analysis of 214 sequences of nuclear small-subunit ribosomal RNA (srRNA) gene undertaken to clarify these evolutionary relationships. We have considered the variability of substitution rates and the nonindependence of nucleotide substitution across sites in the srRNA gene in testing alternative hypotheses regarding the branching patterns of eukaryote phylogeny. We find that the rates of evolution among sites in the srRNA sequences vary substantially and are approximately gamma distributed with size and shape parameter equal to 0.76. Our results suggest that (1) the animals and true fungi are indeed closer to each other than to any other “crown” group in the eukaryote tree, (2) red algae are the closest relatives of animals, true fungi, and green plants, and (3) the heterokonts and alveolates probably evolved prior to the divergence of red algae and animal-fungus-green-plant lineages. Furthermore, our analyses indicate that the branching order of the eukaryotic lineages that diverged prior to the evolution of alveolates may be generally difficult to resolve with the srRNA sequence data.

Key words

Small-subunit ribosomal RNAPhylogenyAnimalsFungiPlantsAlveolatesHeterokontsStramenopiles

Copyright information

© Springer-Verlag New York Inc. 1996

Authors and Affiliations

  • Sudhir Kumar
    • 1
  • Andrey Rzhetsky
    • 1
  1. 1.Institute of Molecular Evolutionary Genetics and Department of Biology, 322 Mueller LaboratoryThe Pennsylvania State UniversityUniversity ParkUSA