Abstract
Interspecific mutualisms are often vulnerable to instability because low benefit : cost ratios can rapidly lead to extinction or to the conversion of mutualism to parasite-host or predator-prey interactions. We hypothesize that the evolutionary stability of mutualism can depend on how benefits and costs to one mutualist vary with the population density of its partner, and that stability can be maintained if a mutualist can influence demographic rates and regulate the population density of its partner. We test this hypothesis in a model of mutualism with key features of senita cactus (Pachycereus schottii)-senita moth (Upiga virescens) interactions, in which benefits of pollination and costs of larval seed consumption to plant fitness depend on pollinator density. We show that plants can maximize their fitness by allocating resources to the production of excess flowers at the expense of fruit. Fruit abortion resulting from excess flower production reduces pre-adult survival of the pollinating seed-consumer, and maintains its density beneath a threshold that would destabilize the mutualism. Such a strategy of excess flower production and fruit abortion is convergent and evolutionarily stable against invasion by cheater plants that produce few flowers and abort few to no fruit. This novel mechanism of achieving evolutionarily stable mutualism, namely interspecific population regulation, is qualitatively different from other mechanisms invoking partner choice or selective rewards, and may be a general process that helps to preserve mutualistic interactions in nature.
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Selected References
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- Abrams PA, Ginzburg LR. The nature of predation: prey dependent, ratio dependent or neither? Trends Ecol Evol. 2000 Aug;15(8):337–341. doi: 10.1016/s0169-5347(00)01908-x. [DOI] [PubMed] [Google Scholar]
- Axelrod R., Hamilton W. D. The evolution of cooperation. Science. 1981 Mar 27;211(4489):1390–1396. doi: 10.1126/science.7466396. [DOI] [PubMed] [Google Scholar]
- Bergstrom Carl T., Lachmann Michael. The Red King effect: when the slowest runner wins the coevolutionary race. Proc Natl Acad Sci U S A. 2003 Jan 13;100(2):593–598. doi: 10.1073/pnas.0134966100. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bronstein Judith L., Wilson William G., Morris William F. Ecological dynamics of mutualist/antagonist communities. Am Nat. 2003 Oct;162(4 Suppl):S24–S39. doi: 10.1086/378645. [DOI] [PubMed] [Google Scholar]
- Bull J. J., Rice W. R. Distinguishing mechanisms for the evolution of co-operation. J Theor Biol. 1991 Mar 7;149(1):63–74. doi: 10.1016/s0022-5193(05)80072-4. [DOI] [PubMed] [Google Scholar]
- Campbell DR. Experimental tests of sex-allocation theory in plants. Trends Ecol Evol. 2000 Jun;15(6):227–232. doi: 10.1016/s0169-5347(00)01872-3. [DOI] [PubMed] [Google Scholar]
- Doebeli M., Knowlton N. The evolution of interspecific mutualisms. Proc Natl Acad Sci U S A. 1998 Jul 21;95(15):8676–8680. doi: 10.1073/pnas.95.15.8676. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ferdy Jean-Baptiste, Després Laurence, Godelle Bernard. Evolution of mutualism between globeflowers and their pollinating flies. J Theor Biol. 2002 Jul 21;217(2):219–234. doi: 10.1006/jtbi.2002.3018. [DOI] [PubMed] [Google Scholar]
- Ferriere Régis, Bronstein Judith L., Rinaldi Sergio, Law Richard, Gauduchon Mathias. Cheating and the evolutionary stability of mutualisms. Proc Biol Sci. 2002 Apr 22;269(1493):773–780. doi: 10.1098/rspb.2001.1900. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Holland J. Nathaniel, DeAngelis Donald L. Ecological and evolutionary conditions for fruit abortion to regulate pollinating seed-eaters and increase plant reproduction. Theor Popul Biol. 2002 May;61(3):251–263. doi: 10.1006/tpbi.2001.1571. [DOI] [PubMed] [Google Scholar]
- Morris William F., Bronstein Judith L., Wilson William G. Three-way coexistence in obligate mutualist-exploiter interactions: the potential role of competition. Am Nat. 2003 Jun 10;161(6):860–875. doi: 10.1086/375175. [DOI] [PubMed] [Google Scholar]
- Thompson J. N. The evolution of species interactions. Science. 1999 Jun 25;284(5423):2116–2118. doi: 10.1126/science.284.5423.2116. [DOI] [PubMed] [Google Scholar]
- West Stuart A., Kiers E. Toby, Simms Ellen L., Denison R. Ford. Sanctions and mutualism stability: why do rhizobia fix nitrogen? Proc Biol Sci. 2002 Apr 7;269(1492):685–694. doi: 10.1098/rspb.2001.1878. [DOI] [PMC free article] [PubMed] [Google Scholar]
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