Evidence of taxa-, clone-, and kin-discrimination in protists: ecological and evolutionary implications
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Unicellular eukaryotes, or protists, are among the most ancient organisms on Earth. Protists belong to multiple taxonomic groups; they are widely distributed geographically and in all environments. Their ability to discriminate among con- and heterospecifics has been documented during the past decade. Here we discuss exemplar cases of taxa-, clone-, and possible kin-discrimination in five major lineages: Mycetozoa (Dictyostelium, Polysphondylium), Dikarya (Saccharomyces), Ciliophora (Tetrahymena), Apicomplexa (Plasmodium) and Archamoebae (Entamoeba). We summarize the proposed genetic mechanisms involved in discrimination-mediated aggregation (self vs. different), including the csA, FLO and trg (formerly lag) genes, and the Proliferation Activation Factors, which facilitate clustering in some protistan taxa. We caution about the experimental challenges intrinsic to studying recognition in protists, and highlight the opportunities for exploring the ecology and evolution of complex forms of cell–cell communication, including social behavior, in a polyphyletic, still superficially understood group of organisms. Because unicellular eukaryotes are the evolutionary precursors of multicellular life, we infer that their mechanisms of taxa-, clone-, and possible kin-discrimination gave origin to the complex diversification and sophistication of traits associated with species and kin recognition in plants, fungi, invertebrates and vertebrates.
KeywordsAltruism Green-beard effect Kin selection Local mate competition Recognition alleles Sex ratio
Horizontal gene transfer
Entamoeba Proliferation Activating Factors
Tetrahymena Proliferation Activating Factors
We thank John A Endler for inviting us to write this article as part of our contribution to the Species Recognition Systems Symposium held in Lisbon, Portugal, August 2013, and sponsored by the European Society for Evolutionary Biology. A Espinosa is supported by NIH grant 8P20GM103430-13. Both authors are sponsored by New England Science Public and the Roger Williams University’s Center for the Public Understanding of Science. Two anonymous reviewers provided valuable comments to improve the manuscript.
Conflict of interest
The authors declare no competing interests.
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