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Proc Biol Sci. 2004 December 7; 271(1556): 2481–2488.
PMCID: PMC1691887

A selection mosaic in the facultative mutualism between ants and wild cotton.


In protection mutualisms, one mutualist defends its partner against a natural enemy in exchange for a reward, usually food or shelter. For both partners, the costs and benefits of these interactions often vary considerably in space because the outcome (positive, negative or neutral) depends on the local abundance of at least three species: the protector, the beneficiary of protection and the beneficiary's natural enemy. In Gossypium thurberi (wild cotton), ants benefit nutritionally from the plant's extrafloral nectaries and guard plants from herbivores. Experimentally altering the availability of both ants and extrafloral nectar in three populations demonstrated that the mutualism is facultative, depending, in part, on the abundance of ants and the level of herbivore damage. The species composition of ants and a parasitic alga that clogs extrafloral nectaries were also implicated in altering the outcome of plant-ant interactions. Furthermore, experimental treatments that excluded ants (the putative selective agents) in combination with phenotypic selection analyses revealed that selection on extrafloral nectary traits was mediated by ants and, importantly, varied across populations. This work is some of the first to manipulate interactions experimentally across multiple sites and thereby document that geographically variable selection, mediated by a mutualist, can shape the evolution of plant traits.

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Selected References

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  • Brodie Edmund D, Jr, Ridenhour BJ, Brodie ED., 3rd The evolutionary response of predators to dangerous prey: hotspots and coldspots in the geographic mosaic of coevolution between garter snakes and newts. Evolution. 2002 Oct;56(10):2067–2082. [PubMed]
  • Gaume L, McKey D, Terrin S. Ant-plant-homopteran mutualism: how the third partner affects the interaction between a plant-specialist ant and its myrmecophyte host. Proc Biol Sci. 1998 Apr 7;265(1396):569–575. [PMC free article]
  • Rudgers Jennifer A, Hodgen Jillian G, White J Wilson., 3rd Behavioral mechanisms underlie an ant-plant mutualism. Oecologia. 2003 Mar;135(1):51–59. [PubMed]
  • Siepielski Adam M, Benkman Craig W. Interactions among moths, crossbills, squirrels, and lodgepole pine in a geographic selection mosaic. Evolution. 2004 Jan;58(1):95–101. [PubMed]
  • Stinchcombe John R, Rausher Mark D. The evolution of tolerance to deer herbivory: modifications caused by the abundance of insect herbivores. Proc Biol Sci. 2002 Jun 22;269(1497):1241–1246. [PMC free article] [PubMed]
  • Thompson John N, Cunningham Bradley M. Geographic structure and dynamics of coevolutionary selection. Nature. 2002 Jun 13;417(6890):735–738. [PubMed]
  • Weeks P. Interactions between red-billed oxpeckers, Buphagus erythrorhynchus, and domestic cattle, Bos taurus, in Zimbabwe. Anim Behav. 1999 Dec;58(6):1253–1259. [PubMed]
  • Zangerl AR, Berenbaum MR. Phenotype matching in wild parsnip and parsnip webworms: causes and consequences. Evolution. 2003 Apr;57(4):806–815. [PubMed]

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