The costs and benefits of being a chimera

Kevin R. Foster, Angelo Fortunato, Joan E. Strassmann, David C. Queller

Research output: Contribution to journalArticle

93 Scopus citations

Abstract

Most multicellular organisms are uniclonal. This is hypothesized to be because uniclonal organisms function better than chimeras (non-clonal organisms), owing to reduced levels of internal genetic conflict. We tested this idea using the social amoeba or slime mold Dictyostelium discoideum. When starving, the normally solitary amoebae aggregate to form a differentiated multicellular slug that migrates towards light and forms a fruiting body, facilitating the dispersal of spores. We added 107 amoebae to Petri plates containing 1, 2, 5 or 10 clones mixed together. We found an intrinsic cost to chimerism: chimeric slugs moved significantly less far than uniclonal slugs of the same size. However, in nature, joining with other clones to form a chimera should increase slug size, and larger slugs travel further. We incorporated this size effect into a second experiment by giving chimeras more cells than single clones (single clones had 106 cells, two-clone chimeras had 2 x 106 cells and so on). The uniclonal treatments then simulated a clone in a mixture that refuses to form chimeras. In this experiment, chimeras moved significantly further than the uniclonal slugs, in spite of the intrinsic cost. Thus, chimerism is costly, which may be why it evolves so seldom, but in D. discoideum the benefits of large size appear to compensate.

Original languageEnglish (US)
Pages (from-to)2357-2362
Number of pages6
JournalProceedings of the Royal Society B: Biological Sciences
Volume269
Issue number1507
DOIs
StatePublished - Nov 22 2002

Keywords

  • Chimera
  • Dictyostelium discoideum
  • Evolution of multicellularity
  • Levels of selection
  • Reproductive conflict

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)

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