Mutualism Parasitism Continuum

The hypothesis or paradigm of Mutualism Parasitism Continuum postulates that compatible host-symbiont associations can occupy a broad continuum of interactions with different fitness outcomes for each member.

At one end of the continuum lies obligate mutualism where both host and symbiont benefit from the interaction and are dependent on it for survival. At the other end of the continuum highly parasitic interactions can occur, where one member gains a fitness benefit at the expense of the others survival. Between these extremes many different types of interaction are possible.[1][2]

The degree of change between mutualism or parasitism varies depending on the availability of resources, where there is environmental stress generated by few resources, symbiotic relationships are formed while in environments where there is an excess of resources, biological interactions turn to competition and parasitism.[3]

Classically the transmission mode of the symbiont can also be important in predicting where on the mutualism-parasitism-continuum an interaction will sit.[4] Symbionts that are vertically transmitted (inherited symbionts) frequently occupy mutualism space on the continuum, this is due to the aligned reproductive interests between host and symbiont that are generated under vertical transmission. In some systems increases in the relative contribution of horizontal transmission can drive selection for parasitism.[5]

Studies of this hypothesis have focused on host-symbiont models of plants and fungi, and also of animals and microbes.

See also

References
  1. Johnson, N. C.; Graham, J. H.; Smith, F. A. (April 1997). "Functioning of mycorrhizal associations along the mutualism-parasitism continuum". New Phytologist. 135 (4): 575–585. doi:10.1046/j.1469-8137.1997.00729.x. ISSN 0028-646X.
  2. Drew, Georgia C.; Stevens, Emily J.; King, Kayla C. (October 2021). "Microbial evolution and transitions along the parasite–mutualist continuum". Nature Reviews Microbiology. 19 (10): 623–638. doi:10.1038/s41579-021-00550-7. ISSN 1740-1534. PMC 8054256. PMID 33875863.
  3. Mandyam, Keerthi G.; Jumpponen, Ari (2015-01-12). "Mutualism–parasitism paradigm synthesized from results of root-endophyte models". Frontiers in Microbiology. 5: 776. doi:10.3389/fmicb.2014.00776. ISSN 1664-302X. PMC 4290590. PMID 25628615.
  4. Ewald, Paul W. (1987). "Transmission Modes and Evolution of the Parasitism-Mutualism Continuuma". Annals of the New York Academy of Sciences. 503 (1): 295–306. Bibcode:1987NYASA.503..295E. doi:10.1111/j.1749-6632.1987.tb40616.x. ISSN 1749-6632. PMID 3304078. S2CID 39350499.
  5. Sachs, Joel L; Wilcox, Thomas P (2006-02-22). "A shift to parasitism in the jellyfish symbiont Symbiodinium microadriaticum". Proceedings of the Royal Society B: Biological Sciences. 273 (1585): 425–429. doi:10.1098/rspb.2005.3346. PMC 1560209. PMID 16615208.


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