Evidence of Taxa-, Clone-, and Kin-discrimination in Protists: Ecological and Evolutionary Implications.
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 versus different), including thecsA,FLOandtrg(formerlylag) genes, and the Proliferation Activation Factors (PAFs), 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.
Department of Biology, Roger Williams University, One Old Ferry Road, Bristol, Rhode Island 02809, USA.
Avelina
A
Espinosa
Department of Biology, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, Massachusetts 02747-2300, USA.
Guillermo
G
Paz-Y-Miño-C
Altruism; Green-beard effect; Kin selection; Local mate competition; Recognition alleles; Sex ratio