Allelopathy as an emergent, exploitable public good in the bloom-forming microalga prymnesium parvum

William W. Driscoll, Noelle J. Espinosa, Omar T. Eldakar, Jeremiah D. Hackett

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Many microbes cooperatively secrete extracellular products that favorably modify their environment. Consistent with social evolution theory, structured habitats play a role in maintaining these traits in microbial model systems, by localizing the benefits and separating strains that invest in these products from 'cheater' strains that benefit without paying the cost. It is thus surprising that many unicellular, well-mixed microalgal populations invest in extracellular toxins that confer ecological benefits upon the entire population, for example, by eliminating nutrient competitors (allelopathy). Here we test the hypotheses that microalgal exotoxins are (1) exploitable public goods that benefit all cells, regardless of investment, or (2) nonexploitable private goods involved in cell-level functions. We test these hypotheses with high-toxicity (TOX+) and low-toxicity (TOX-) strains of the damaging, mixotrophic microalga Prymnesium parvum and two common competitors: green algae and diatoms. TOX+ actually benefits from dense populations of competing green algae, which can also be prey for P. parvum, yielding a relative fitness advantage over coexisting TOX-. However, with nonprey competitors (diatoms), TOX- increases in frequency over TOX+, despite benefiting from the exclusion of diatoms by TOX+. An evolutionary unstable, ecologically devastating public good may emerge from traits selected at lower levels expressed in novel environments.

Original languageEnglish (US)
Pages (from-to)1582-1590
Number of pages9
Issue number6
StatePublished - Jun 2013


  • Cooperation
  • Multilevel selection
  • Prymnesium parvum
  • Public goods
  • Toxic algal bloom


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